AQA GCSE Combined Science: Trilogy Chemistry Paper 1 (Higher), 2024: Question 1

✅ Correct answers

Any two valid conclusions score the 2 marks. Acceptable answers include:

• The mass of copper produced increased from 1900 to 2010.
• Before about 1930, the mass of copper produced increased only slightly.
• After about 1930, the mass of copper produced increased rapidly.
• The highest mass of copper was produced in 2010.
• The lowest mass of copper was produced in 1900.
• The increase was not linear.

💡 Key knowledge

• A conclusion must come from the graph, not from outside knowledge.
• You can comment on a trend, a comparison, or a highest/lowest value.
• The graph curves upwards, so the increase is getting faster over time.
• The mark scheme allows about 1925 to 1930 as the turning point.

🧠 Exam technique

• For “give two conclusions”, write two separate clear statements.
• Use the graph language: increased, highest, lowest, rapidly, slightly, not linear.
• If possible, include dates to make your point precise.
• Do not explain why the trend happened unless the question asks you to.

❌ Common errors

• Copying exact numbers incorrectly from the graph.
• Saying “it increased steadily” — this is wrong because the increase is not linear.
• Giving reasons such as “more demand for copper” — not needed and not from the graph.
• Repeating the same idea twice in different words.

Examiner insight: Students often lost marks by making vague comments like “it went up a lot”. Stronger answers described how the trend changed, for example “slight increase before 1930, rapid increase after 1930”.

✅ Correct answer

A full-mark answer should include all three ideas:

• The atoms are different sizes.
• This distorts the layers.
• So the layers cannot easily slide over each other.

💡 Key knowledge

• Pure metals have regular layers of atoms.
• Those regular layers can slide more easily.
• In an alloy, atoms of different sizes disrupt the regular arrangement.
• This makes movement of layers more difficult, so the metal is harder.

🧠 Exam technique

• The question says Use Figure 2, so refer to the different-sized atoms shown.
• For 3 marks, build a chain of reasoning.
• Best structure: different sizes → distorted layers → cannot slide easily → harder

❌ Common errors

• Saying “the alloy is harder because zinc is hard” — not the marking point.
• Talking about stronger bonds — the mark scheme wants the sliding/layer idea.
• Forgetting to mention that the atoms are different sizes.
• Saying only “the structure is different” without explaining the effect on layers.

Examiner insight: Top answers linked the particle diagram directly to hardness. Weaker answers often stopped at “different sizes” and did not explain that this prevents layers sliding.

✅ Correct answer

Mass of copper = 4.54 g (to 3 significant figures)

📐 Calculations

Method 1: Find % copper first

1. Percentage of copper = 100 − 13.5 = 86.5%
2. Mass of copper = 86.5/100 × 5.25
3. Mass of copper = 4.54125 g
4. Round to 3 significant figures = 4.54 g

Method 2: Find zinc mass, then subtract

1. Mass of zinc = 13.5/100 × 5.25 = 0.70875 g
2. Mass of copper = 5.25 − 0.70875 = 4.54125 g
3. Round to 3 significant figures = 4.54 g

💡 Key knowledge

• Percentage by mass tells you how much of the total mass is one substance.
• If zinc is 13.5%, then copper must be 86.5%.
• To find a percentage of a mass: percentage ÷ 100 × total mass
• Always give the final answer with the correct unit: g.

🧠 Exam technique

• Show all working — this is a 4-mark calculation.
• Write the percentage conversion clearly before using it.
• Do not round too early; round only at the end.
• Check if your answer is sensible: copper should be most of the 5.25 g because 86.5% is much more than half.

❌ Common errors

• Using 13.5% as the percentage of copper instead of zinc.
• Doing 5.25 ÷ 13.5 or another incorrect percentage method.
• Forgetting to divide by 100.
• Rounding to 4.5 g instead of 3 significant figures.
• Missing the unit g.

Examiner insight: Many students got part way through correctly but lost the final mark by not rounding to 3 significant figures. The best responses showed a full method and then wrote a clearly labelled final answer.

✅ 01.1 Graph conclusions

Choose any two valid trend statements, such as:

• Production increased from 1900 to 2010.
• After about 1930, production increased rapidly.

✅ 01.2 Alloy hardness

Use this chain:

different-sized atoms → distorted layers → layers cannot slide easily → harder

✅ 01.3 Calculation

100 − 13.5 = 86.5% copper

86.5/100 × 5.25 = 4.54125 g

Answer = 4.54 g