Energy changesHigherpractical skillscalorimetryenergy changes
AQA GCSE · Question 04.3 · Energy changes
Explain why using a polystyrene cup gives more accurate results than using a glass beaker.
How to approach this question
1. Compare the properties of polystyrene and glass in terms of heat transfer. Which one is a better insulator?
2. How does this property affect the experiment, which involves measuring a temperature change? What error is being reduced?
Full Answer
Polystyrene is a better thermal insulator than glass. This reduces heat loss to the surroundings, meaning the measured temperature change is closer to the true value.
This experiment measures the temperature change of a reaction, a technique called calorimetry. A major source of inaccuracy in calorimetry is the loss of thermal energy to the surroundings.
1. **Polystyrene is a good thermal insulator:** This means it does not conduct heat well.
2. **Glass is a better thermal conductor:** It allows heat to pass through it more easily.
By using a polystyrene cup, less heat from the exothermic reaction is lost to the air and the lab bench. This ensures that the measured temperature rise is as large as possible and therefore closer to the actual temperature change of the reaction, leading to a more accurate result.
Common mistakes
✗ Just saying "it keeps the heat in" without explaining why (i.e., it's an insulator).
✗ Saying polystyrene "prevents" heat loss - it only reduces it.
✗ Not comparing polystyrene to glass.
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