Explain why two substances made of different materials but with the same mass require different amounts of energy to reach the same temperature rise.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A student heats equal masses of water and cooking oil using identical immersion heaters for the same length of time. She notices that the cooking oil reaches a higher temperature than the water.
Model answer (4 marks)
Different substances have different specific heat capacities.
Specific heat capacity is the amount of energy needed to raise the temperature of 1 kg of a substance by 1 °C.
Water has a higher specific heat capacity than cooking oil, so it requires more energy for the same temperature rise.
Since the same amount of energy is supplied to both, the substance with the lower specific heat capacity (cooking oil) reaches a higher temperature.
Specific heat capacity is the amount of energy needed to raise the temperature of 1 kg of a substance by 1 °C.
Water has a higher specific heat capacity than cooking oil, so it requires more energy for the same temperature rise.
Since the same amount of energy is supplied to both, the substance with the lower specific heat capacity (cooking oil) reaches a higher temperature.
Examiner tips
- Use the term ‘specific heat capacity’ explicitly. Show the logical chain: different c → different energy for ΔT. Mention that equal masses and equal energy input give different ΔT.
- common_mistakes
- :
- Confusing specific heat capacity with heat of fusion. Saying ‘water heats slower’ instead of ‘requires more energy’. Using ‘mass’ instead of ‘specific heat capacity’ to explain the temperature difference.
Mark scheme (4 marks)
- Different substances have different specific heat capacities
- Specific heat capacity is the amount of energy needed to raise the temperature of 1 kg of a substance by 1 °C
- Water has a higher specific heat capacity than cooking oil, so it requires more energy for the same temperature rise
- Since the same amount of energy is supplied to both, the substance with the lower specific heat capacity (cooking oil) reaches a higher temperature
Key terms in this question
Related
- All Cambridge International IGCSE Physics (0625) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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