AQA GCSE Chemistry Chemistry Paper 1 (Foundation), November 2021: Question 4

9 marks · Low Demand difficulty · Short Answer

Investigate the reactivity of metals with hydrochloric acid using temperature change data and an exothermic reaction profile diagram.

Practise this question

Question

Question 4 displays a method for investigating metal reactivity using temperature changes when added to hydrochloric acid. Table 4 lists temperature increases across four trials for cobalt (6, 7, 5, 9; mean 7), magnesium (54, 50, 37, 55; mean X), and zinc (18, 16, 18, 20; mean 18). Sub-questions include calculating the mean for magnesium excluding an anomaly, deducing the reactivity order, finding the uncertainty for zinc, identifying the variable type for acid volume, suggesting an improvement to measuring metal powder, and labelling an exothermic reaction profile diagram with components A, B, and C.
Question text

04 A student investigated the reactivity of metals with hydrochloric acid.

This is the method used.

1. Measure 50 cm3 of hydrochloric acid into a polystyrene cup.

2. Measure the temperature of the hydrochloric acid.

3. Add one spatula of metal powder to the hydrochloric acid and stir.

4. Measure the highest temperature the mixture reaches.

5. Calculate the temperature increase for the reaction.

6. Repeat steps 1 to 5 three more times.

7. Repeat steps 1 to 6 with different metals.

Table 4 shows the student’s results.

Table 4

Temperature increase in °C Mean

Metal temperature

Trial 1 Trial 2 Trial 3 Trial 4 increase in °C

Cobalt 6 7 5 9 7

Magnesium 54 50 37 55 X

Zinc 18 16 18 20 18

04.1 Calculate the mean temperature increase X for magnesium in Table 4.

Do not include the anomalous result in your calculation.

[2 marks]

17 X =

°C

04.2 Determine the order of reactivity for the metals cobalt, magnesium and zinc.

Use Table 4.

[1 mark]

Most reactive

Least reactive

04.3 The range of measurements either side of the mean shows the uncertainty in the

mean temperature increase.

Complete the sentence.

Use Table 4.

[1 mark]

The mean temperature increase for zinc is 18 ± °C

04.4 What type of variable is the volume of hydrochloric acid in this investigation?

[1 mark]

Tick ( ) one box.

Control

Dependent

Independent

04.5 Suggest one way of improving step 3 in the method to give results which are more

repeatable.

[1 mark]

04.6 Figure 6 shows a reaction profile for the reaction of magnesium with

hydrochloric acid.

Figure 6

What do labels A, B and C represent on Figure 6?

Choose answers from the box.

[3 marks]

activation energy energy overall energy change

products progress of reaction reactants

A

B

C

Mark scheme

Show the mark scheme Mark scheme for Question 4 outlines acceptable answers: 04.1 requires (54 + 50 + 55)/3 = 53 °C (2 marks); 04.2 requires magnesium, zinc, cobalt (1 mark); 04.3 requires 2 (1 mark); 04.4 requires 'control' (1 mark); 04.5 requires using the same mass of metal or powder (1 mark); 04.6 identifies A as progress of reaction, B as activation energy, and C as products (3 marks). Total marks: 9.

Question 4

AO /

Question Answers Extra information Mark

Spec. Ref.

04.1

54 + 50 + 55 1 AO3

= 53 (°C) 1 AO2

if no other mark awarded allow 1

mark for 4.4.1.2

4.5.1.1

54 + 50 + 37 + 55

= 49 (°C)

AO /

Spec. Ref.

04.2 allow ecf from question 04.1 AO3

(most reactive) magnesium 1 4.4.1.2

zinc 4.5.1.1

(least reactive) cobalt RPA4

AO /

Spec. Ref.

04.3 (18 ±) 2 (°C) 1 AO2

4.3.1.4

AO /

Spec. Ref.

control 1 AO1

04.4 4.4.1.2

4.5.1.1

RPA4

Question 4 continued

AO /

Spec. Ref.

04.5 use the same mass of metal / 1 AO3

14 powder 4.4.1.2

4.5.1.1

RPA4

AO /

Spec. Ref.

04.6 (A) progress of reaction 1 AO1

4.5.1.2

(B) activation energy 1

(C) products 1

Total 9

How to answer it

Investigating Metal Reactivity & Energy Changes

📌 What this question tests

This question focuses on Required Practical 4 (Temperature changes) and Chemical Changes (Reactivity Series):

  • Identifying anomalous data and calculating an accurate mean.
  • Deducing a reactivity series from exothermic temperature increases.
  • Calculating experimental measurement uncertainty ( ± uncertainty ).
  • Distinguishing between independent, dependent, and control variables.
  • Evaluating methods to improve experimental repeatability.
  • Labeling exothermic reaction profile diagrams correctly.

Part (a) — Question 04.1

Mean Temperature Calculation (Excluding Anomalies)

📐 Step-by-Step Calculation

Step 1: Spot the anomaly
Trials for Magnesium: 54, 50, 37, 55.
37 °C is significantly lower than the other three values (it is anomalous).
Step 2: Calculate the mean of normal trials
Total = 54 + 50 + 55 = 159
Mean = 159 ÷ 3 = 53 °C
X = 53 °C

❌ Common Errors

  • Including 37: Adding all four numbers (54 + 50 + 37 + 55) ÷ 4 = 49 °C . This only gets 1 compensation mark.
  • Dividing by 4 after ignoring 37: Always divide by the number of valid trials used (3)!
Mark Scheme: 1 mark for correct working (54 + 50 + 55) ÷ 3 ; 1 mark for final answer of 53 .

Part (b) — Question 04.2

Deducing Order of Reactivity

✅ Correct Answer

Most reactive: Magnesium (53 °C)

Middle: Zinc (18 °C)

Least reactive: Cobalt (7 °C)

💡 Key Knowledge

The reaction of metals with acid is exothermic (gives out heat energy). A more reactive metal reacts faster and more vigorously, transferring more energy to the surroundings in a short time, leading to a higher temperature rise.

🧠 Exam Technique

Always double-check the direction: does the prompt ask for most reactive to least or least to most? Here, "Most reactive" is at the top.

Mark Scheme: 1 mark for correct order: Magnesium, Zinc, Cobalt. (Allow error carried forward from 04.1 if calculated value changes order).

Part (c) — Question 04.3

Determining Measurement Uncertainty

✅ Correct Answer

The mean temperature increase for zinc is 18 ± 2 °C

📐 How Uncertainty is Found

  • Trials for Zinc: 18, 16, 18, 20. Mean = 18.
  • Method 1 (Distance from mean): The lowest value is 16 (18 − 2) and highest is 20 (18 + 2). Hence ± 2.
  • Method 2 (Half the range): Range = 20 − 16 = 4.
    Uncertainty = Range ÷ 2 = 4 ÷ 2 = 2.

❌ Common Errors

  • Writing the full range (4) instead of half the range (2).
  • Writing ±18 instead of reading what comes after the "±" sign.
Mark Scheme: 1 mark for 2 .

Parts (d) & (e) — Questions 04.4 & 04.5

Variables and Practical Improvements

Question 04.4: Variable Type

Correct Box: [✔] Control

  • Independent: The metal used (what is changed).
  • Dependent: Temperature increase (what is measured).
  • Control: Volume of acid, concentration of acid (kept constant for a fair test).

Question 04.5: Improving Repeatability

Correct Answer:

Use the same mass of metal / powder (or weigh the metal using a balance).

Why "one spatula" is poor: A spatula is not a scientific unit of measurement! Spatula scoops vary wildly in mass, causing spread in results.
Mark Scheme 04.4: 1 mark for "Control".
Mark Scheme 04.5: 1 mark for "use the same mass of metal / powder" or measuring with a balance.

Part (f) — Question 04.6

Reaction Profiles

✅ Correct Labels

  • A: progress of reaction
  • B: activation energy
  • C: products

💡 Reaction Profile Rules

  • Horizontal Axis (A): Represents time or the progress of reaction.
  • Vertical Arrow (B): From reactant level to the peak of the curve is always the activation energy (the minimum energy needed for particles to react).
  • Final Level (C): Represents the chemicals formed at the end, which are the products.
  • Since products are lower than reactants, overall energy is released (exothermic).

❌ Common Errors

  • Confusing activation energy (from reactants to peak) with overall energy change (from reactants to products).
  • Mixing up reactants (start of curve) and products (end of curve).
Mark Scheme: 1 mark each for A (progress of reaction), B (activation energy), C (products). Total = 3 marks.

Topics

Chemistry · Required Practicals · C4: Chemical Changes · C5: Energy Changes · Required Practicals · C3: Quantitative Chemistry

Question and mark scheme from the AQA GCSE Chemistry examination, Chemistry Paper 1 (Foundation), November 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.