AQA GCSE Combined Science: Trilogy Chemistry Paper 1 (Foundation), 2023: Question 2

8 marks · Low Demand difficulty · Short Answer

Identify lab equipment, calculate mean temperature change, and explain reactivity differences in a metal displacement reaction investigation.

Practise this question

Question

A multi-part exam question about an investigation into the temperature change when magnesium is added to zinc sulfate solution. It includes a diagram of a beaker containing 50 cubic centimeters of solution and magnesium with a thermometer labeled X. There is a table showing temperature increases for three experiments (7.6, 7.3, and 7.6 degrees Celsius) and a placeholder Y for the mean. Questions ask to identify equipment, calculate the mean, use proportionality to find a temperature increase for a different mass of magnesium, identify the reaction type, and explain why copper does not react.
Question text

02 A student investigated the temperature change when magnesium was added to

zinc sulfate solution.

Figure 5 shows the apparatus.

Figure 5

02.1 Which piece of equipment is labelled X?

[1 mark]

Tick ( ) one box.

Beaker

Ruler

Thermometer

02.2 Which piece of equipment is the best to use to measure volumes of solution?

[1 mark]

Tick ( ) one box.

Conical flask

Evaporating basin

Measuring cylinder 9

The student added 1.0 g of magnesium to 50 cm3 of zinc sulfate solution and

measured the temperature increase.

The student repeated the experiment two more times.

*08* Table 1 shows the results.

Table 1

Temperature increase in °C

Experiment 1 Experiment 2 Experiment 3 Mean

7.6 7.3 7.6 Y

02.3 Calculate value Y in Table 1.

[2 marks]

Y = °C

02.4 The student then added 1.2 g of magnesium to 50 cm3 of zinc sulfate solution.

The temperature increased by 9.0 °C.

Calculate the temperature increase when the student adds 0.40 g of magnesium

to 50 cm3 of zinc sulfate solution.

[2 marks]

10 Temperature increase = °C

02.5 What is the name given to a reaction which causes the temperature to increase?

[1 mark]

Tick ( ) one box.

Endothermic

Exothermic

Thermal decomposition

02.6 The student repeated the experiment with 1.2 g of copper and

50 cm3 of zinc sulfate solution.

The temperature did not increase.

Give one reason why.

[1 mark]

Mark scheme

Show the mark scheme The mark scheme for question 2 shows the correct answers and marking points. For 02.1, the answer is thermometer. For 02.2, it is measuring cylinder. For 02.3, the calculation for the mean Y is (7.6 + 7.3 + 7.6) / 3 = 7.5. For 02.4, the calculation is (0.40 / 1.2) * 9.0 = 3.0. For 02.5, the answer is exothermic. For 02.6, the reason is that copper did not react or is less reactive than zinc.

Question 2

AO /

Question Answers Extra information Mark

Spec. Ref.

02.1 thermometer 1 AO1

5.4.1.2

5.5.1.1

RPA10

AO /

Spec. Ref.

02.2 measuring cylinder 1 AO1

5.4.1.2

5.5.1.1

RPA10

AO /

Spec. Ref.

02.3 7.6 + 7.3 + 7.6 22.5 AO2

(Y =) or 1

33 5.4.1.2

5.5.1.1

RPA10

= 7.5 (°C) 1

allow for 2 marks

7.6 + 7.6

(Y =) = 7.6 (°C)

AO /

Spec. Ref.

02.4 (temperature increase =) AO2

0.40 5.4.1.2

× 9.0 1

1.2 5.5.1.1

RPA10

= 3.0 (°C) 1

AO /

Spec. Ref.

02.5 exothermic 1 AO1

5.5.1.1

RPA10

AO /

Spec. Ref.

02.6 copper did not react (with zinc 1 AO3

sulfate) 5.4.1.2

or 5.5.1.1

copper is less reactive (than allow copper is less reactive RPA10

zinc) (than magnesium)

Total Question 2 8

How to answer it

Temperature Changes in Displacement Reactions

What this question tests

This question assesses your ability to identify laboratory equipment, calculate mean values from experimental data, use proportionality in chemical reactions, and apply the Reactivity Series to explain why certain reactions do not occur.

Parts 02.1 & 02.2

Laboratory Equipment

Identifying tools for measurement

Correct Answers

  • 02.1: Thermometer
  • 02.2: Measuring cylinder

Key Knowledge

A thermometer measures temperature change. A measuring cylinder is the standard tool for measuring liquid volumes accurately in a school lab.

Exam Technique

Beakers and conical flasks often have volume markings, but they are approximate. If a question asks for the "best" way to measure volume, always choose measuring cylinder or pipette/burette.

Part 02.3

Calculating the Mean

Finding the average temperature increase

Step-by-Step Calculation

  1. Add the three results together: 7.6 + 7.3 + 7.6 = 22.5
  2. Divide the total by the number of experiments (3): 22.5 / 3 = 7.5
  3. Final Answer Y = 7.5 °C

Common Errors

Students often forget to press "=" on their calculator after adding the numbers and before dividing. If you type 7.6 + 7.3 + 7.6 / 3 , the calculator only divides the last number by 3!

Mark Scheme Note: 1 mark for the correct working, 1 mark for the correct answer. The examiner also allows 7.6 if you treated 7.3 as an anomaly and averaged the two 7.6 values.

Part 02.4

Proportionality

Predicting results based on mass

Step-by-Step Calculation

We know that 1.2 g of Magnesium gives a 9.0 °C increase. We need to find the increase for 0.40 g.

  1. Find the ratio of the masses: 0.40 / 1.2 = 1/3 (or 0.333...)
  2. Apply this ratio to the temperature: 9.0 × (0.40 / 1.2) = 3.0
  3. Final Answer = 3.0 °C

Examiner Insight

Top-level responses spotted that 0.40 g is exactly one-third of 1.2 g. Therefore, the temperature increase will also be exactly one-third of 9.0 °C.

Part 02.5

Energy Changes

Naming the reaction type

Correct Answer

Exothermic

Key Knowledge

  • Exothermic: Energy is released to the surroundings. The temperature of the solution increases.
  • Endothermic: Energy is taken in from the surroundings. The temperature of the solution decreases.
Part 02.6

The Reactivity Series

Why some reactions don't happen

Correct Answer

Copper is less reactive than zinc (so it cannot displace it).

Key Knowledge

In a displacement reaction, a more reactive metal takes the place of a less reactive metal in a compound. Because copper is lower than zinc in the reactivity series, no reaction occurs, and no heat is released.

Common Errors

Avoid saying "Copper is not reactive enough." You must compare it to the other metal. Use the phrase "less reactive than zinc" to secure the mark.

Topics

Chemistry · C4: Chemical Changes · C5: Energy Changes

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Chemistry Paper 1 (Foundation), 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.