Question 1 (2 marks)
Calculation
Temperature rises from 19.5 °C to 26.0 °C. Calculate change.
Show model answer / marking points
26.0 − 19.5 = 6.5 °C (2).
Required Practical 10: Temperature Changes | AQA GCSE Science | The Science Department
About this practical and its aim
Aim
Investigate factors affecting temperature changes during reactions in solution.
Introduction
When chemical reactions occur, there is a change in energy. In this practical, you will be able to measure that change and work out the energy change. The level of complexity can vary, you can record a temperature change; work out an energy change using the specific heat capacity of water; energy change per gram of reactant and finally, you could work out the energy change per mole. Key learning is also around assessing the practical's reliability and accuracy. Look at ways of improving this experiment to get consistent answers around the class.
The science behind the practical
Exothermic reactions transfer energy to surroundings, usually increasing measured temperature; endothermic processes can lower it.
Key things to remember
Measure starting and highest/lowest temperatures; keep reactant quantities consistent unless they are the variable.
Equipment and apparatus
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Polystyrene cup and lid
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beaker
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thermometer or temperature probe
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measuring cylinders
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appropriate dilute reactants
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stirrer
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balance where relevant
Method: How to carry out the experiment
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Into a polystyrene cup, add 50cm3 of tap water
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For improved stability, stand the cup inside a glass beaker
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Place a thermometer into the water and record the initial temperature
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Carefully measure out 5g of calcium chloride (replace the lid)
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Add the calcium chloride to the water and place plastic lid on and put the thermometer through the hole into the solution
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Record the highest or lowest temperature achieved = final temperature.
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Calculate the temperature change: the difference between "initial temperature" and "final temperature".
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Once completed, your teacher may ask you to repeat the same experiment to assess accuracy or to repeat with a different mass of calcium chloride to see if you get the same energy grange per gram (or mole), which you should.
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Energy change = mass of water (50) x temperature change x 4.2 (SHC of water)
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To find the energy change per gram, divide the above answer by 5 (as 5g added).
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(Higher tier) - try to calculate the energy change per mole.
Variables and fair testing
| Type of variable | What is measured or controlled? |
|---|---|
| Independent variable | Concentration, volume, mass or identity of a reactant |
| Dependent variable | Temperature change (°C) |
| Control variables | Insulation; initial temperature; stirring; vessel and thermometer; timing |
Safety and managing risks
Follow your teacher's instructions and your school's risk assessment. This page is not a substitute for a formal risk assessment.
| Hazard | Risk | Precaution |
|---|---|---|
Reactive solutions |
Irritation or burns depending on reagents |
Use approved quantities/concentrations and eye protection as assessed. |
Rapid temperature changes |
Hot solutions and container warming |
Mix controlled amounts and handle vessel carefully. |
Results, calculations and analysis
Recording, presenting and interpreting results
Table: changed variable, initial temperature (°C), peak/minimum temperature (°C), temperature change (°C). Graph the temperature change against the chosen variable.
Calculations
Temperature change = final or extreme temperature − initial temperature; energy transfer estimate Q = mcΔT when appropriate.
Conclusions, accuracy and evaluation
Drawing a conclusion
Changing the amount or concentration of reactant can change the measured temperature change.
Evaluating the investigation
Use an insulated polystyrene cup with lid, stir consistently and record temperature promptly to reduce heat exchange.
More to learn
Heat-transfer limitations
Some energy transfers to the surroundings rather than changing the measured solution temperature; improve insulation.
Common exam mistake
Use the highest or lowest measured temperature as appropriate, not necessarily the reading at the end of the lesson.
GCSE examination practice
Answer each question in full before opening the model answer. Check your work against the marking points and look for scientific key words.
Question 2 (1 marks)
Knowledge
What does a rise in solution temperature usually suggest?
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An exothermic reaction transferred energy to surroundings (1).
Question 3 (2 marks)
Evaluation
Suggest two ways to reduce energy loss during this investigation.
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Use a polystyrene cup (1); fit a lid or insulate surroundings (1).
Question 4 (2 marks)
Evaluation
Suggest one improvement to make the investigation more reliable and explain why it helps.
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Repeat measurements and calculate a mean (1), reducing the influence of random variation/anomalies (1). Alternative valid improvement specific to the experiment with explanation can gain both marks.
This page was updated on: 17th June 2026