Grade 12 Physical Sciences Chemistry — Limpopo practice
Notes
Answer every question. Show the formula, the substitution, and the answer with units. Calculators allowed. These are original practice papers in the style of the province, not a copy of a department PDF.
120 min · 91 Marks · 30 questions
Learn the paper in the app: notes, a marks breakdown, the formula you need, and the board working. You do not need to download it.
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: CH₃CH₂OH is named
Before any working — hunt first
Given
Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: CH₃CH₂OH is named. Circle that word — that is the missing variable.
Find
We are required to find: CH₃CH₂OH is named. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: Two carbons, an −OH on carbon 1: ethanol. Then substitute the given, one line at a time, to get CH₃CH₂OH is named.
In other words — as if you have never seen this before
Two carbons, an −OH on carbon 1: ethanol.
2. What do we already know?
CH₃CH₂OH is named
3. Which method — and why this one?
Two carbons, an −OH on carbon 1: ethanol.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: CH₃CH₂OH is named. Circle that word — that is the missing variable.
Find: We are required to find: CH₃CH₂OH is named. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: Two carbons, an −OH on carbon 1: ethanol. Then substitute the given, one line at a time, to get CH₃CH₂OH is named.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
CH₃CH₂OH is named
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
Two carbons, an −OH on carbon 1: ethanol.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
Two carbons, an −OH on carbon 1: ethanol.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
ethanol
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
ethanol
Copy onto your answer sheet — in this order
Answer: ethanol
6. Check it like a marker
Two carbons, an −OH on carbon 1: ethanol.
7. A trap first-timers fall into
ethanoic acid
1.2 · 6 Marks
[H₃O⁺]=1×10⁻3. pH=
Notes: [H₃O⁺]=1×10⁻3. pH=
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: [H₃O⁺] = 1 × 10⁻3. pH =
Before any working — hunt first
Given
Numbers and units already in the sentence: 1 · 10⁻ · 3. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: pH =. Circle that word — that is the missing variable.
Find
We are required to find: pH =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: pH = −log(10⁻3) = 3. Then substitute the given, one line at a time, to get pH =.
In other words — as if you have never seen this before
pH = −log(10⁻3) = 3. Write two decimal places: 3.00.
2. What do we already know?
[H₃O⁺]=1×10⁻3. pH=
3. Which method — and why this one?
pH = −log(10⁻3) = 3. Write two decimal places: 3.00.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: 1 · 10⁻ · 3. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: pH =. Circle that word — that is the missing variable.
Find: We are required to find: pH =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: pH = −log(10⁻3) = 3. Then substitute the given, one line at a time, to get pH =.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
[H₃O⁺]=1×10⁻3. pH=
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
pH = −log(10⁻3) = 3. Write two decimal places: 3.00.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
pH = −log(10⁻3) = 3. Write two decimal places: 3.00.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
3.00
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
3.00
Copy onto your answer sheet — in this order
Answer: 3.00
6. Check it like a marker
pH = −log(10⁻3) = 3. Write two decimal places: 3.00.
7. A trap first-timers fall into
11
2.1 · 6 Marks · Chemical equilibrium
A catalyst in an equilibrium
Chemical equilibrium
Formulas
Kc=[C]ᶜ [D]ᵈ[A]ᵃ [B]ᵇ
Equilibrium constant
Notes: A catalyst in an equilibrium
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: A catalyst in an equilibrium
Before any working — hunt first
Given
Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: A catalyst in an equilibrium. Circle that word — that is the missing variable.
Find
We are required to find: A catalyst in an equilibrium. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: Both activation energies drop. Then substitute the given, one line at a time, to get A catalyst in an equilibrium.
In other words — as if you have never seen this before
Both activation energies drop. K_c stays the same.
2. What do we already know?
A catalyst in an equilibrium
3. Which method — and why this one?
Both activation energies drop. K_c stays the same.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: A catalyst in an equilibrium. Circle that word — that is the missing variable.
Find: We are required to find: A catalyst in an equilibrium. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: Both activation energies drop. Then substitute the given, one line at a time, to get A catalyst in an equilibrium.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
A catalyst in an equilibrium
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
Both activation energies drop. K_c stays the same.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
Both activation energies drop. K_c stays the same.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
speeds both directions and leaves K_c unchanged
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
speeds both directions and leaves K_c unchanged
Copy onto your answer sheet — in this order
Answer: speeds both directions and leaves K_c unchanged
6. Check it like a marker
Both activation energies drop. K_c stays the same.
7. A trap first-timers fall into
increases the yield
2.2 · 8 Marks
Zn E° = −0.76 V and Cu E° = +0.34 V. E°cell =
Notes: Zn E° = −0.76 V and Cu E° = +0.34 V. E°cell =
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: Zn E° = −0.76 V and Cu E° = +0.34 V. E°cell =
Before any working — hunt first
Given
Numbers and units already in the sentence: 0.76 V · 0.34 V. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: E°cell =. Circle that word — that is the missing variable.
Find
We are required to find: E°cell =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: E°cell = 0. Then substitute the given, one line at a time, to get E°cell =.
In other words — as if you have never seen this before
E°cell = 0.34 − (−0.76) = 1.10 V. Copper is the cathode.
2. What do we already know?
Zn E° = −0.76 V and Cu E° = +0.34 V. E°cell =
3. Which method — and why this one?
E°cell = 0.34 − (−0.76) = 1.10 V. Copper is the cathode.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: 0.76 V · 0.34 V. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: E°cell =. Circle that word — that is the missing variable.
Find: We are required to find: E°cell =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: E°cell = 0. Then substitute the given, one line at a time, to get E°cell =.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Zn E° = −0.76 V and Cu E° = +0.34 V. E°cell =
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
E°cell = 0.34 − (−0.76) = 1.10 V. Copper is the cathode.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
E°cell = 0.34 − (−0.76) = 1.10 V. Copper is the cathode.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
1.10 V
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
1.10 V
Copy onto your answer sheet — in this order
Answer: 1.10 V
6. Check it like a marker
E°cell = 0.34 − (−0.76) = 1.10 V. Copper is the cathode.
7. A trap first-timers fall into
0.42 V
3.1 · 6 Marks
Haber uses about 450 °C because
Notes: Haber uses about 450 °C because
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: Haber uses about 450 °C because
Before any working — hunt first
Given
Numbers and units already in the sentence: 450 °C. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: Haber uses about 450 °C because. Circle that word — that is the missing variable.
Find
We are required to find: Haber uses about 450 °C because. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: Low T favours yield. Then substitute the given, one line at a time, to get Haber uses about 450 °C because.
In other words — as if you have never seen this before
Low T favours yield. High T favours rate. 450 °C is the factory compromise.
2. What do we already know?
Haber uses about 450 °C because
3. Which method — and why this one?
Low T favours yield. High T favours rate. 450 °C is the factory compromise.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: 450 °C. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: Haber uses about 450 °C because. Circle that word — that is the missing variable.
Find: We are required to find: Haber uses about 450 °C because. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: Low T favours yield. Then substitute the given, one line at a time, to get Haber uses about 450 °C because.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Haber uses about 450 °C because
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
Low T favours yield. High T favours rate. 450 °C is the factory compromise.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
Low T favours yield. High T favours rate. 450 °C is the factory compromise.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
it is a compromise between rate and yield
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
it is a compromise between rate and yield
Copy onto your answer sheet — in this order
Answer: it is a compromise between rate and yield
6. Check it like a marker
Low T favours yield. High T favours rate. 450 °C is the factory compromise.
7. A trap first-timers fall into
the reaction is endothermic
3.2 · 8 Marks
In a Polokwane school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Notes: In a Polokwane school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: In a Polokwane school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Before any working — hunt first
Given
Numbers and units already in the sentence: 0.40 mol·dm⁻³ · 16 s. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: Average rate =. Circle that word — that is the missing variable.
Find
We are required to find: Average rate =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: rate = 0. Then substitute the given, one line at a time, to get Average rate =.
In other words — as if you have never seen this before
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
2. What do we already know?
In a Polokwane school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
3. Which method — and why this one?
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: 0.40 mol·dm⁻³ · 16 s. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: Average rate =. Circle that word — that is the missing variable.
Find: We are required to find: Average rate =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: rate = 0. Then substitute the given, one line at a time, to get Average rate =.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
In a Polokwane school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
0.025 mol·dm⁻³·s⁻¹
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
0.025 mol·dm⁻³·s⁻¹
Copy onto your answer sheet — in this order
Answer: 0.025 mol·dm⁻³·s⁻¹
6. Check it like a marker
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
7. A trap first-timers fall into
6.4 mol·dm⁻³·s⁻¹
7 · 3 Marks · Rates of reaction
A catalyst speeds a reaction because it
Rates of reaction
Formulas
rate=ΔcΔt
Change in concentration over time
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: A catalyst speeds a reaction because it
Before any working — hunt first
Given
Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: A catalyst speeds a reaction because it. Circle that word — that is the missing variable.
Find
We are required to find: A catalyst speeds a reaction because it. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: Lower E_a means a larger fraction of collisions succeed. Then substitute the given, one line at a time, to get A catalyst speeds a reaction because it.
In other words — as if you have never seen this before
Lower E_a means a larger fraction of collisions succeed. The catalyst is regenerated.
2. What do we already know?
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
Lower E_a means a larger fraction of collisions succeed. The catalyst is regenerated.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: A catalyst speeds a reaction because it. Circle that word — that is the missing variable.
Find: We are required to find: A catalyst speeds a reaction because it. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: Lower E_a means a larger fraction of collisions succeed. Then substitute the given, one line at a time, to get A catalyst speeds a reaction because it.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
Lower E_a means a larger fraction of collisions succeed. The catalyst is regenerated.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
Lower E_a means a larger fraction of collisions succeed. The catalyst is regenerated.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
opens a path with a lower activation energy
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
opens a path with a lower activation energy
Copy onto your answer sheet — in this order
Answer: opens a path with a lower activation energy
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
8 · 2 Marks
The molecular formula of butane is
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: The molecular formula of butane is
Before any working — hunt first
Given
Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: The molecular formula of butane is. Circle that word — that is the missing variable.
Find
We are required to find: The molecular formula of butane is. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: C₄H₁₀. Then substitute the given, one line at a time, to get The molecular formula of butane is.
In other words — as if you have never seen this before
C₄H₁₀
2. What do we already know?
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
C₄H₁₀
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: The molecular formula of butane is. Circle that word — that is the missing variable.
Find: We are required to find: The molecular formula of butane is. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: C₄H₁₀. Then substitute the given, one line at a time, to get The molecular formula of butane is.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
C₄H₁₀
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Reason
An alkane is CₙH₂ₙ₊₂. For n = 4, C₄H₁₀.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
C₄H₁₀
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
C₄H₁₀
Copy onto your answer sheet — in this order
Answer: C₄H₁₀
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
9 · 4 Marks
Haber uses ~450 °C because
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: Haber uses ~450 °C because
Before any working — hunt first
Given
Numbers and units already in the sentence: 450 °C. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: Haber uses ~450 °C because. Circle that word — that is the missing variable.
Find
We are required to find: Haber uses ~450 °C because. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: Exothermic wants low T for yield; factory wants high T for rate. Then substitute the given, one line at a time, to get Haber uses ~450 °C because.
In other words — as if you have never seen this before
Exothermic wants low T for yield; factory wants high T for rate.
2. What do we already know?
Copy these onto the left of your page, one per line, with units: 450 °C. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
Exothermic wants low T for yield; factory wants high T for rate.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: 450 °C. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: Haber uses ~450 °C because. Circle that word — that is the missing variable.
Find: We are required to find: Haber uses ~450 °C because. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: Exothermic wants low T for yield; factory wants high T for rate. Then substitute the given, one line at a time, to get Haber uses ~450 °C because.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: 450 °C. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
Exothermic wants low T for yield; factory wants high T for rate.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
Exothermic wants low T for yield; factory wants high T for rate.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
it is a compromise between rate and yield
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
it is a compromise between rate and yield
Copy onto your answer sheet — in this order
Answer: it is a compromise between rate and yield
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
10 · 3 Marks
Zn −0.76 V, Cu +0.34 V. E°cell
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: Zn −0.76 V, Cu +0.34 V. E°cell
Before any working — hunt first
Given
Numbers and units already in the sentence: 0.76 V · 0.34 V. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: E°cell. Circle that word — that is the missing variable.
Find
We are required to find: E°cell. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: 1. Then substitute the given, one line at a time, to get E°cell.
In other words — as if you have never seen this before
1.10 V
2. What do we already know?
Copy these onto the left of your page, one per line, with units: 0.76 V · 0.34 V. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
1.10 V
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: 0.76 V · 0.34 V. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: E°cell. Circle that word — that is the missing variable.
Find: We are required to find: E°cell. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: 1. Then substitute the given, one line at a time, to get E°cell.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: 0.76 V · 0.34 V. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
1.10 V
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Reason
0.34−(−0.76)=1.10 V.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
1.10 V
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
1.10 V
Copy onto your answer sheet — in this order
Answer: 1.10 V
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
11 · 2 Marks · Chemical equilibrium
N₂(g) + 3H₂(g) ⇌ 2NH₃(g). Raising the pressure shifts the equilibrium
Chemical equilibrium
Formulas
Kc=[C]ᶜ [D]ᵈ[A]ᵃ [B]ᵇ
Equilibrium constant
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: N₂(g) + 3H₂(g) ⇌ 2NH₃(g). Raising the pressure shifts the equilibrium
In other words — as if you have never seen this before
to the right
2. What do we already know?
Copy these onto the left of your page, one per line, with units: 3H · 2NH. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
to the right
4. Step-by-step working
01 / 07
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 07
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: 3H · 2NH. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
03 / 07
Step C — Name the method in words
to the right
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
04 / 07
Reason
4 mol of gas become 2 mol. Higher pressure favours the side with fewer moles.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
05 / 07
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
06 / 07
Step F — Box the answer with its unit
to the right, toward fewer gas molecules
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
07 / 07
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
to the right, toward fewer gas molecules
Copy onto your answer sheet — in this order
Answer: to the right, toward fewer gas molecules
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
12 · 2 Marks · Rates of reaction
Powdered zinc fizzes faster than a lump in the same acid because
Rates of reaction
Formulas
rate=ΔcΔt
Change in concentration over time
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: Powdered zinc fizzes faster than a lump in the same acid because
In other words — as if you have never seen this before
Same reaction. More surface, more collisions that can succeed.
2. What do we already know?
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
Same reaction. More surface, more collisions that can succeed.
4. Step-by-step working
01 / 07
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 07
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
03 / 07
Step C — Name the method in words
Same reaction. More surface, more collisions that can succeed.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
04 / 07
Working
Same reaction. More surface, more collisions that can succeed.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
05 / 07
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
06 / 07
Step F — Box the answer with its unit
more surface means more collisions per second
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
07 / 07
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
more surface means more collisions per second
Copy onto your answer sheet — in this order
Answer: more surface means more collisions per second
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
13 · 2 Marks
In a Bloemfontein school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Notes: In a Bloemfontein school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: In a Bloemfontein school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Before any working — hunt first
Given
Numbers and units already in the sentence: 0.40 mol·dm⁻³ · 16 s. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: Average rate =. Circle that word — that is the missing variable.
Find
We are required to find: Average rate =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: rate = 0. Then substitute the given, one line at a time, to get Average rate =.
In other words — as if you have never seen this before
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
2. What do we already know?
In a Bloemfontein school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
3. Which method — and why this one?
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: 0.40 mol·dm⁻³ · 16 s. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: Average rate =. Circle that word — that is the missing variable.
Find: We are required to find: Average rate =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: rate = 0. Then substitute the given, one line at a time, to get Average rate =.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
In a Bloemfontein school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
0.025 mol·dm⁻³·s⁻¹
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
0.025 mol·dm⁻³·s⁻¹
Copy onto your answer sheet — in this order
Answer: 0.025 mol·dm⁻³·s⁻¹
6. Check it like a marker
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
7. A trap first-timers fall into
6.4 mol·dm⁻³·s⁻¹
14 · 2 Marks
C₄H₁₀ has two chain isomers. They are
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: C₄H₁₀ has two chain isomers. They are
Before any working — hunt first
Given
Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: They are. Circle that word — that is the missing variable.
Find
We are required to find: They are. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: butane and 2-methylpropane. Then substitute the given, one line at a time, to get They are.
In other words — as if you have never seen this before
butane and 2-methylpropane
2. What do we already know?
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
butane and 2-methylpropane
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: They are. Circle that word — that is the missing variable.
Find: We are required to find: They are. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: butane and 2-methylpropane. Then substitute the given, one line at a time, to get They are.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
butane and 2-methylpropane
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Reason
Same formula, different carbon chain. Butene is C₄H₈.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
butane and 2-methylpropane
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
butane and 2-methylpropane
Copy onto your answer sheet — in this order
Answer: butane and 2-methylpropane
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
15 · 2 Marks
Ethanol plus ethanoic acid, with an acid catalyst, makes
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: Ethanol plus ethanoic acid, with an acid catalyst, makes
In other words — as if you have never seen this before
an ester and water
2. What do we already know?
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
an ester and water
4. Step-by-step working
01 / 07
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 07
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
03 / 07
Step C — Name the method in words
an ester and water
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
05 / 07
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
06 / 07
Step F — Box the answer with its unit
an ester and water
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
07 / 07
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
an ester and water
Copy onto your answer sheet — in this order
Answer: an ester and water
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
16 · 2 Marks
The functional group of an alcohol is
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: The functional group of an alcohol is
Before any working — hunt first
Given
Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: The functional group of an alcohol is. Circle that word — that is the missing variable.
Find
We are required to find: The functional group of an alcohol is. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: hydroxyl, –OH. Then substitute the given, one line at a time, to get The functional group of an alcohol is.
In other words — as if you have never seen this before
hydroxyl, –OH
2. What do we already know?
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
hydroxyl, –OH
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: The functional group of an alcohol is. Circle that word — that is the missing variable.
Find: We are required to find: The functional group of an alcohol is. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: hydroxyl, –OH. Then substitute the given, one line at a time, to get The functional group of an alcohol is.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
hydroxyl, –OH
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Reason
Name the alcohol with the -ol ending and the number on the carbon that holds the OH.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
hydroxyl, –OH
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
hydroxyl, –OH
Copy onto your answer sheet — in this order
Answer: hydroxyl, –OH
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
17 · 2 Marks
If [H₃O⁺] = 1.0 × 10⁻⁵, then [OH⁻] =
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: If [H₃O⁺] = 1.0 × 10⁻⁵, then [OH⁻] =
Before any working — hunt first
Given
Numbers and units already in the sentence: 1.0 · 10⁻. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: 0 × 10⁻⁵, then [OH⁻] =. Circle that word — that is the missing variable.
Find
We are required to find: 0 × 10⁻⁵, then [OH⁻] =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: 1. Then substitute the given, one line at a time, to get 0 × 10⁻⁵, then [OH⁻] =.
In other words — as if you have never seen this before
1.0 × 10⁻⁹
2. What do we already know?
Copy these onto the left of your page, one per line, with units: 1.0 · 10⁻. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
1.0 × 10⁻⁹
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: 1.0 · 10⁻. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: 0 × 10⁻⁵, then [OH⁻] =. Circle that word — that is the missing variable.
Find: We are required to find: 0 × 10⁻⁵, then [OH⁻] =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: 1. Then substitute the given, one line at a time, to get 0 × 10⁻⁵, then [OH⁻] =.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: 1.0 · 10⁻. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
1.0 × 10⁻⁹
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Reason
[OH⁻]=Kw[H₃O⁺]=10⁻¹⁴10⁻⁵=10⁻⁹.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
1.0 × 10⁻⁹
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
1.0 × 10⁻⁹
Copy onto your answer sheet — in this order
Answer: 1.0 × 10⁻⁹
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
18 · 2 Marks · Electrochemistry
An electrolytic cell
Formulas
E°cell=E°cathode−E°anode
Standard cell potential
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: An electrolytic cell
Before any working — hunt first
Given
Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: An electrolytic cell. Circle that word — that is the missing variable.
Find
We are required to find: An electrolytic cell. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: needs an external source. Then substitute the given, one line at a time, to get An electrolytic cell.
In other words — as if you have never seen this before
needs an external source
2. What do we already know?
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
needs an external source
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: An electrolytic cell. Circle that word — that is the missing variable.
Find: We are required to find: An electrolytic cell. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: needs an external source. Then substitute the given, one line at a time, to get An electrolytic cell.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
needs an external source
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Reason
The power supply forces a non-spontaneous redox reaction.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
needs an external source of electrical energy
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
needs an external source of electrical energy
Copy onto your answer sheet — in this order
Answer: needs an external source of electrical energy
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
19 · 2 Marks
At 25 °C, K_w is
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: At 25 °C, K_w is
Before any working — hunt first
Given
Numbers and units already in the sentence: 25 °C. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: At 25 °C, K_w is. Circle that word — that is the missing variable.
Find
We are required to find: At 25 °C, K_w is. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: 1. Then substitute the given, one line at a time, to get At 25 °C, K_w is.
In other words — as if you have never seen this before
1.0 × 10⁻¹⁴
2. What do we already know?
Copy these onto the left of your page, one per line, with units: 25 °C. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
1.0 × 10⁻¹⁴
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: 25 °C. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: At 25 °C, K_w is. Circle that word — that is the missing variable.
Find: We are required to find: At 25 °C, K_w is. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: 1. Then substitute the given, one line at a time, to get At 25 °C, K_w is.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: 25 °C. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
1.0 × 10⁻¹⁴
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Reason
[H₃O⁺][OH⁻] = 1.0 × 10⁻¹⁴. Each is 10⁻⁷ in pure water.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
1.0 × 10⁻¹⁴
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
1.0 × 10⁻¹⁴
Copy onto your answer sheet — in this order
Answer: 1.0 × 10⁻¹⁴
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
20 · 3 Marks
Zn E°=−0.76 V, Cu E°=+0.34 V. E°cell=
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: Zn E° = −0.76 V, Cu E° = +0.34 V. E°cell =
Before any working — hunt first
Given
Numbers and units already in the sentence: 0.76 V · 0.34 V. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: E°cell =. Circle that word — that is the missing variable.
Find
We are required to find: E°cell =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: E°cell = 0. Then substitute the given, one line at a time, to get E°cell =.
In other words — as if you have never seen this before
E°cell = 0.34 − (−0.76) = 1.10 V. Cu is cathode.
2. What do we already know?
Copy these onto the left of your page, one per line, with units: 0.76 V · 0.34 V. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
E°cell = 0.34 − (−0.76) = 1.10 V. Cu is cathode.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: 0.76 V · 0.34 V. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: E°cell =. Circle that word — that is the missing variable.
Find: We are required to find: E°cell =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: E°cell = 0. Then substitute the given, one line at a time, to get E°cell =.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: 0.76 V · 0.34 V. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
E°cell = 0.34 − (−0.76) = 1.10 V. Cu is cathode.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
E°cell = 0.34 − (−0.76) = 1.10 V. Cu is cathode.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
1.10 V
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
1.10 V
Copy onto your answer sheet — in this order
Answer: 1.10 V
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
21 · 2 Marks · Chemical equilibrium
For an exothermic forward reaction, heating the mixture shifts equilibrium
Chemical equilibrium
Formulas
Kc=[C]ᶜ [D]ᵈ[A]ᵃ [B]ᵇ
Equilibrium constant
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: For an exothermic forward reaction, heating the mixture shifts equilibrium
In other words — as if you have never seen this before
to the left
2. What do we already know?
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
to the left
4. Step-by-step working
01 / 07
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 07
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
03 / 07
Step C — Name the method in words
to the left
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
04 / 07
Reason
Heat is a product. Adding heat favours the reverse, endothermic direction.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
05 / 07
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
06 / 07
Step F — Box the answer with its unit
to the left
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
07 / 07
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
to the left
Copy onto your answer sheet — in this order
Answer: to the left
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
22 · 2 Marks
HBr adds to ethene to give
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: HBr adds to ethene to give
Before any working — hunt first
Given
Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: HBr adds to ethene to give. Circle that word — that is the missing variable.
Find
We are required to find: HBr adds to ethene to give. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: bromoethane. Then substitute the given, one line at a time, to get HBr adds to ethene to give.
In other words — as if you have never seen this before
bromoethane
2. What do we already know?
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
bromoethane
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: HBr adds to ethene to give. Circle that word — that is the missing variable.
Find: We are required to find: HBr adds to ethene to give. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: bromoethane. Then substitute the given, one line at a time, to get HBr adds to ethene to give.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
bromoethane
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Reason
Addition across the double bond. No ultraviolet light is required.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
bromoethane
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
bromoethane
Copy onto your answer sheet — in this order
Answer: bromoethane
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
23 · 2 Marks
[H₃O⁺]=1×10⁻2. pH=
Notes: [H₃O⁺]=1×10⁻2. pH=
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: [H₃O⁺] = 1 × 10⁻2. pH =
Before any working — hunt first
Given
Numbers and units already in the sentence: 1 · 10⁻ · 2. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: pH =. Circle that word — that is the missing variable.
Find
We are required to find: pH =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: pH = −log(10⁻2) = 2. Then substitute the given, one line at a time, to get pH =.
In other words — as if you have never seen this before
pH = −log(10⁻2) = 2. Write two decimal places: 2.00.
2. What do we already know?
[H₃O⁺]=1×10⁻2. pH=
3. Which method — and why this one?
pH = −log(10⁻2) = 2. Write two decimal places: 2.00.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: 1 · 10⁻ · 2. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: pH =. Circle that word — that is the missing variable.
Find: We are required to find: pH =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: pH = −log(10⁻2) = 2. Then substitute the given, one line at a time, to get pH =.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
[H₃O⁺]=1×10⁻2. pH=
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
pH = −log(10⁻2) = 2. Write two decimal places: 2.00.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
pH = −log(10⁻2) = 2. Write two decimal places: 2.00.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
2.00
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
2.00
Copy onto your answer sheet — in this order
Answer: 2.00
6. Check it like a marker
pH = −log(10⁻2) = 2. Write two decimal places: 2.00.
7. A trap first-timers fall into
12
24 · 2 Marks
In a Mahikeng school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Notes: In a Mahikeng school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: In a Mahikeng school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Before any working — hunt first
Given
Numbers and units already in the sentence: 0.40 mol·dm⁻³ · 16 s. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: Average rate =. Circle that word — that is the missing variable.
Find
We are required to find: Average rate =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: rate = 0. Then substitute the given, one line at a time, to get Average rate =.
In other words — as if you have never seen this before
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
2. What do we already know?
In a Mahikeng school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
3. Which method — and why this one?
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: 0.40 mol·dm⁻³ · 16 s. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: Average rate =. Circle that word — that is the missing variable.
Find: We are required to find: Average rate =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: rate = 0. Then substitute the given, one line at a time, to get Average rate =.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
In a Mahikeng school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
0.025 mol·dm⁻³·s⁻¹
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
0.025 mol·dm⁻³·s⁻¹
Copy onto your answer sheet — in this order
Answer: 0.025 mol·dm⁻³·s⁻¹
6. Check it like a marker
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
7. A trap first-timers fall into
6.4 mol·dm⁻³·s⁻¹
25 · 2 Marks
The Haber process makes ammonia using
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: The Haber process makes ammonia using
Before any working — hunt first
Given
Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: The Haber process makes ammonia using. Circle that word — that is the missing variable.
Find
We are required to find: The Haber process makes ammonia using. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: N₂, H₂ and iron. Then substitute the given, one line at a time, to get The Haber process makes ammonia using.
In other words — as if you have never seen this before
N₂, H₂ and iron
2. What do we already know?
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
N₂, H₂ and iron
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: The Haber process makes ammonia using. Circle that word — that is the missing variable.
Find: We are required to find: The Haber process makes ammonia using. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: N₂, H₂ and iron. Then substitute the given, one line at a time, to get The Haber process makes ammonia using.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
N₂, H₂ and iron
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Reason
N₂ + 3H₂ ⇌ 2NH₃. Iron is the catalyst. V₂O₅ is the Contact process.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
N₂, H₂ and an iron catalyst
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
N₂, H₂ and an iron catalyst
Copy onto your answer sheet — in this order
Answer: N₂, H₂ and an iron catalyst
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
26 · 2 Marks
CH₃CH₂CH₂OH is named
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: CH₃CH₂CH₂OH is named
Before any working — hunt first
Given
Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: CH₃CH₂CH₂OH is named. Circle that word — that is the missing variable.
Find
We are required to find: CH₃CH₂CH₂OH is named. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: CAPS: number before −ol, with hyphens. Then substitute the given, one line at a time, to get CH₃CH₂CH₂OH is named.
In other words — as if you have never seen this before
CAPS: number before −ol, with hyphens. Not 1-propanol.
2. What do we already know?
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
CAPS: number before −ol, with hyphens. Not 1-propanol.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: CH₃CH₂CH₂OH is named. Circle that word — that is the missing variable.
Find: We are required to find: CH₃CH₂CH₂OH is named. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: CAPS: number before −ol, with hyphens. Then substitute the given, one line at a time, to get CH₃CH₂CH₂OH is named.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
CAPS: number before −ol, with hyphens. Not 1-propanol.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
CAPS: number before −ol, with hyphens. Not 1-propanol.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
propan-1-ol
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
propan-1-ol
Copy onto your answer sheet — in this order
Answer: propan-1-ol
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
27 · 2 Marks
Propene is
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: Propene is
Before any working — hunt first
Given
Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: Propene is. Circle that word — that is the missing variable.
Find
We are required to find: Propene is. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: unsaturated. Then substitute the given, one line at a time, to get Propene is.
In other words — as if you have never seen this before
unsaturated
2. What do we already know?
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
unsaturated
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: Propene is. Circle that word — that is the missing variable.
Find: We are required to find: Propene is. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: unsaturated. Then substitute the given, one line at a time, to get Propene is.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
unsaturated
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Reason
The double bond can still add atoms.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
an unsaturated hydrocarbon
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
an unsaturated hydrocarbon
Copy onto your answer sheet — in this order
Answer: an unsaturated hydrocarbon
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
28 · 2 Marks
In a Gqeberha school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Notes: In a Gqeberha school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: In a Gqeberha school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Before any working — hunt first
Given
Numbers and units already in the sentence: 0.40 mol·dm⁻³ · 16 s. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: Average rate =. Circle that word — that is the missing variable.
Find
We are required to find: Average rate =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: rate = 0. Then substitute the given, one line at a time, to get Average rate =.
In other words — as if you have never seen this before
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
2. What do we already know?
In a Gqeberha school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
3. Which method — and why this one?
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: 0.40 mol·dm⁻³ · 16 s. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: Average rate =. Circle that word — that is the missing variable.
Find: We are required to find: Average rate =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: rate = 0. Then substitute the given, one line at a time, to get Average rate =.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
In a Gqeberha school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
0.025 mol·dm⁻³·s⁻¹
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
0.025 mol·dm⁻³·s⁻¹
Copy onto your answer sheet — in this order
Answer: 0.025 mol·dm⁻³·s⁻¹
6. Check it like a marker
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
7. A trap first-timers fall into
6.4 mol·dm⁻³·s⁻¹
29 · 2 Marks
The functional group of ethanoic acid is
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: The functional group of ethanoic acid is
Before any working — hunt first
Given
Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: The functional group of ethanoic acid is. Circle that word — that is the missing variable.
Find
We are required to find: The functional group of ethanoic acid is. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: carboxyl. Then substitute the given, one line at a time, to get The functional group of ethanoic acid is.
In other words — as if you have never seen this before
carboxyl
2. What do we already know?
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
3. Which method — and why this one?
carboxyl
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: no numbers yet — only a name, a diagram, or a worded unknown. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: The functional group of ethanoic acid is. Circle that word — that is the missing variable.
Find: We are required to find: The functional group of ethanoic acid is. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: carboxyl. Then substitute the given, one line at a time, to get The functional group of ethanoic acid is.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
Copy these onto the left of your page, one per line, with units: every number and its unit in the sentence. Mixing cm with m, or minutes with seconds, loses a method mark.
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
carboxyl
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Reason
–COOH is the carboxyl group. An alcohol is only –OH.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
carboxyl
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
carboxyl
Copy onto your answer sheet — in this order
Answer: carboxyl
6. Check it like a marker
Does your answer appear as one of the options? Do the units match what was asked (m, N, J, °)? If you put the number back into the original equation, does it still hold? Estimate: is the size sensible?
7. A trap first-timers fall into
First-timers often grab the first formula they remember, mix units (cm with m, minutes with seconds), or drop a minus sign. Write the formula in words first: “this equals that, because…”
30 · 2 Marks
In a Kimberley school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Notes: In a Kimberley school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
How we got there
Read this like a teacher at the board. We go slowly, name every number, and say why we take each step.
Explain in another language · 11
1. What is the question asking?
Read the question twice. Circle the unknown. Underline every number and unit. The paper is asking: In a Kimberley school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Before any working — hunt first
Given
Numbers and units already in the sentence: 0.40 mol·dm⁻³ · 16 s. Copy each one into a column. A name without a number is not given.
Missing
After you copy the given, the letter that still has no number is missing. The paper is pointing at: Average rate =. Circle that word — that is the missing variable.
Find
We are required to find: Average rate =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate
What we need to calculate: rate = 0. Then substitute the given, one line at a time, to get Average rate =.
In other words — as if you have never seen this before
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
2. What do we already know?
In a Kimberley school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
3. Which method — and why this one?
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
4. Step-by-step working
01 / 08
Step A — Read the question twice
Slow down. Circle the word that names the unknown. Underline every number and its unit. Do not grab a formula yet — first decide what the paper is actually asking.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
02 / 08
Step A2 — Hunt: Given, Missing, Find, Calculate
Given: Numbers and units already in the sentence: 0.40 mol·dm⁻³ · 16 s. Copy each one into a column. A name without a number is not given.
Missing: After you copy the given, the letter that still has no number is missing. The paper is pointing at: Average rate =. Circle that word — that is the missing variable.
Find: We are required to find: Average rate =. Write that as a symbol on the left, with a question mark, before you touch a formula.
Calculate: What we need to calculate: rate = 0. Then substitute the given, one line at a time, to get Average rate =.
Why this step: Do not name the letters yet. First hunt: what already has a number (Given), what has no number (Missing), the word the paper wants (Find), and which formula still contains the missing letter (Calculate).
03 / 08
Step B — Write the given in a column
In a Kimberley school lab, concentration falls by 0.40 mol·dm⁻³ in 16 s. Average rate =
Why this step: A column with units stops you mixing cm with m, or minutes with seconds. Markers can also see you started correctly.
04 / 08
Step C — Name the method in words
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
Why this step: If you can say the method in a sentence, you will pick the right formula. First-timers skip this and grab the first equation they remember.
05 / 08
Working
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.
Why this step: We only do one job per line so a marker can follow the marks — and so you can find a slip without starting over.
06 / 08
Step G — Sense-check the size
Ask: is this the kind of number a Grade 10–12 paper would want? A speed of 3 000 ms for a learner walking, or a probability bigger than 1, means a unit or algebra slip. Estimate first: round the numbers and do the sum in your head.
Why this step: Markers write ‘unrealistic’ in the margin when the method is right but the size is wild. A 10-second head check often finds a missing 10² or a unit that never changed.
07 / 08
Step F — Box the answer with its unit
0.025 mol·dm⁻³·s⁻¹
Why this step: A number without a unit is half a mark on a Physics paper, and a marker can miss a Maths answer that is buried in working.
08 / 08
Step H — What the marker is looking for
On an NSC memo you usually earn: (1) a method mark for naming the right formula or idea in words, (2) an accuracy mark for substituting the given numbers with units, (3) an accuracy mark for the boxed answer with its unit. Write those three lines even if you are unsure of the arithmetic — blank pages score zero.
Why this step: First-timers chase the final number and leave the method blank. The memo still pays out for the idea and the substitution even when the last line is wrong.
5. The answer
0.025 mol·dm⁻³·s⁻¹
Copy onto your answer sheet — in this order
Answer: 0.025 mol·dm⁻³·s⁻¹
6. Check it like a marker
rate = 0.4016=0.025 mol·dm⁻³·s⁻¹. Heat would raise the fraction of collisions that reach E_a.