AQA GCSE Combined Science: Trilogy Chemistry Paper 1 (Foundation), 2021: Question 5
11 marks · Standard Demand difficulty · Short Answer
Analyze an investigation into the temperature change when zinc is added to copper sulfate solution, including experimental improvements, data extraction, reaction classification, gradient calculation, and prediction.
Practise this questionQuestion
Question text
05 A student investigated the change in temperature when different masses of zinc were
added to copper sulfate solution.
This is the method used.
1. Measure the volume of copper sulfate solution using a measuring cylinder.
2. Pour the copper sulfate solution into a metal container.
3. Add 2 g of zinc.
4. Measure the temperature of the solution.
5. Repeat steps 1 to 4 with different masses of zinc.
Figure 7 shows the apparatus.
Figure 7
05.1 Give three improvements to the investigation to make the results more accurate.
[3 marks]
05.2 Figure 8 shows part of the measuring cylinder.
Figure 8
What is the volume of copper sulfate solution in Figure 8?
[1 mark]
Volume = cm3
05.3 When zinc was added to copper sulfate solution the temperature increased.
Figure 9 shows the reaction profile.
Figure 9
What type of reaction is shown in Figure 9?
[1 mark]
Tick ( ) one box.
Endothermic Exothermic18 Neutralisation
Figure 10 shows the results.
Figure 10
05.4 Determine the gradient of the line in Figure 10.
Use the equation:
increase in temperature in °C
gradient =
increase in mass in grams
[4 marks]
Gradient = °C per g
05.5 Suggest why the student should not use more than 10 g of zinc.
Use Figure 10.
You should extend the graph line.
[2 marks]
Mark scheme
Show the mark scheme
AO /
Question Answers Extra information Mark
Spec. Ref.
05.1 any three from: 3 AO3
5.5.1.1
• use a (glass) beaker
or
use a polystyrene cup
• insulate the metal container
• add a lid
• measure copper sulfate
solution with a pipette
• use same volume (of copper
sulfate solution)
• use a more accurate balance
• stir (the mixture)
• record the initial and the
highest temperature
• use a digital thermometer
or
use a more accurate
thermometer
• repeat the experiment and
calculate the mean (ignoring
anomalous results)
05.2 72 (cm3) 1 AO2
5.4.3.1
5.4.3.4
RPA9
05.3 exothermic 1 AO2
5.5.1.2
05.4 (increase in temperature =) AO2
50 (°C) 1 5.4.3.1
5.4.3.4
increase in mass = 6 (g) allow a value in the range 1 RPA9
5.8 – 6 (g)
50 13
(gradient = ) allow correct use of incorrectly 1
6 determined value(s) for
temperature and/or mass
= 8.33 (°C per g) 1
05.5 extends line on graph to 10 g of 1 AO2
zinc
any one from: 1
• temperature (change) of allow a temperature (change)
84 (°C) over 80 (°C) AO3
• (so the solution will be)
too hot 5.4.3.1
5.4.3.4
• (so the solution will be) RPA9
over 100 (°C)
• (so the solution will) boil
Total 11
How to answer it
Investigating Temperature Changes in Reactions
What this question tests
This question assesses your understanding of Exothermic Reactions and Practical Skills. You need to know how to reduce heat loss in experiments, read scales accurately, interpret energy level diagrams, and calculate gradients from experimental data.
Improving Experimental Accuracy
💡 Key Knowledge
In temperature change experiments, the biggest source of error is heat loss to the surroundings. Metal is a good conductor, so using a metal container (as shown in Figure 7) is a poor choice.
🧠 Exam Technique
When asked for "improvements," think about the equipment. If they use a beaker, suggest a polystyrene cup. If it's open, suggest a lid. If it's a manual thermometer, suggest a digital one.
✅ Correct Answers (Choose any three)
- Use a polystyrene cup (better insulator than metal).
- Add a lid to reduce heat loss to the air.
- Insulate the container (e.g., place it in a beaker of cotton wool).
- Stir the mixture to ensure the temperature is even throughout.
- Use a digital thermometer for more precise readings.
Reading Scales
✅ Correct Answer
72 cm³
🧠 How to read Figure 8
Look at the scale: there are 5 small divisions between 60 and 70. This means each small line represents 2 cm³. The liquid level is one line above 70.
❌ Common Error
Students often assume each line is 1 unit. If you wrote 71 cm³, you missed the scale increment!
Reaction Profiles
💡 Energy Changes
- Exothermic: Products have less energy than reactants (energy is released).
- Endothermic: Products have more energy than reactants (energy is absorbed).
✅ Correct Answer
Exothermic
The line for the products is lower than the line for the reactants, showing energy has been lost to the surroundings.
Calculating the Gradient
📐 Step-by-Step Calculation
- Identify the change in Y (Temperature): The graph shows an increase from 0 to 50. So, Change = 50 °C .
- Identify the change in X (Mass): The line ends at 6g. So, Change = 6 g .
- Apply the formula: 50 / 6
- Calculate: 8.333...
- Final Answer: 8.33 °C per g
🧠 Examiner Tip
Even if you get the numbers slightly wrong from the graph, you can still get "Error Carried Forward" marks if you show your division clearly. Always write down your working!
Extrapolating Data
🧠 Visualizing the Answer
The question asks you to extend the line. If you use a ruler to continue the straight line from Figure 10 up to 10g on the x-axis, you will see the temperature change reaches approximately 84 °C.
✅ Correct Answer
- The temperature change would be approx 84 °C.
- The solution would boil or be too hot (over 100 °C).
💡 Why 100 °C?
Copper sulfate solution is mostly water. Water boils at 100 °C. If the increase is 84 °C and the room temperature was 20 °C, the final temp would be 104 °C—which is impossible for liquid water at standard pressure!
Topics
Chemistry · C5: Energy Changes · C6: The Rate and Extent of Chemical Change
Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Chemistry Paper 1 (Foundation), 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.