AQA GCSE Combined Science: Trilogy Chemistry Paper 1 (Higher), 2019: Question 1

✅ Correct answer

Ca Mg Zn Cu

So the correct tick is Ca Mg Zn Cu.

💡 Key knowledge

• More reactive metals react more vigorously with acids.
• Calcium is more reactive than magnesium, zinc, and copper.
• Copper is the least reactive here and does not react with dilute hydrochloric acid.

🧠 Exam technique

Use the pattern of bubbles. More bubbles = more hydrogen gas made = faster reaction = more reactive metal.

To score the mark, you only need the correct order in the box.

❌ Common errors

• Putting copper above zinc because it is “heavier” or “looks more shiny”.
• Mixing up magnesium and zinc.
• Writing the right metals but in the wrong order.

✅ Correct answers

• Same volume of hydrochloric acid
• Same concentration of hydrochloric acid
• Same mass of metal
• Same size/surface area of metal pieces
• Same temperature

Any two sensible control variables score the 2 marks.

💡 Key knowledge

A fair test means only the type of metal should change. Everything else must stay the same so the results can be compared properly.

🧠 Exam technique

Good answers are specific. For example:

same volume of acid is better than just same acid .

❌ Common errors

• Saying “same metal” — that changes the variable being tested.
• Writing “keep it constant” without saying what it is.
• Using vague answers like “same conditions” with no detail.

✅ Correct answer

The type of metal used.

💡 Key knowledge

The independent variable is the thing you deliberately change. Here, the student changes the metal to see how it reacts with hydrochloric acid.

🧠 Exam technique

If a question asks about variables, link your answer to the experiment:

metal is the thing being compared; the acid is kept the same.

❌ Common errors

• Saying “hydrochloric acid” — that is not the thing being changed.
• Saying “the reaction” — too vague.

✅ Correct answer

Beryllium is less reactive than magnesium.

Reason: They are both in Group 2, and reactivity increases down the group. Beryllium is above magnesium in the periodic table, so it is less reactive.

💡 Key knowledge

• Group 2 metals all have 2 outer electrons.
• Down Group 2, atoms get larger and the outer electrons are further from the nucleus.
• Because of this, the outer electrons are lost more easily, so reactivity increases down the group.

🧠 Exam technique

To get both marks, include:

• a comparison word: more or less reactive
• a periodic table reason: beryllium is above magnesium in Group 2

❌ Common errors

• Saying beryllium is more reactive because it is “higher up” without the Group 2 trend.
• Giving no comparison with magnesium.
• Confusing Group 2 with Group 1 trends.

📐 Calculations step-by-step

1. Write down the mass and volume given: 3.2 g in 50 cm³.
2. Convert the volume to dm³: 50 cm³ = 0.050 dm³.
3. Use concentration = mass ÷ volume.
4. Calculate: 3.2 ÷ 0.050 = 64.

Answer = 64 g per dm³

💡 Key knowledge

For concentration in g per dm³:

concentration = mass ÷ volume

Make sure the volume is in dm³, not cm³.

🧠 Exam technique

Show the conversion clearly to earn method marks:

50 cm³ ÷ 1000 = 0.050 dm³

Always include units in the final answer.

❌ Common errors

• Using 50 cm³ directly in the calculation.
• Dividing the wrong way round.
• Writing 64 g/cm³ instead of 64 g/dm³.
• Missing the unit completely.

💡 What top answers did well

• Used the reactivity pattern correctly from the metal observations.
• Gave specific control variables for a fair test.
• Explained beryllium using Group 2 and the periodic table.
• Showed the calculation method with correct unit conversion.

❌ Where students lose marks

• Confusing independent and control variables.
• Being too vague in explanation questions.
• Forgetting to convert cm³ to dm³.
• Not giving the final unit.