A student investigates the specific heat capacity of water by heating a known mass of water using an immersion heater and recording the temperature at regular time intervals. Describe how the student can ensure their results are as accurate and reliable as possible, and explain why it is important to stir the water throughout the experiment.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Specific heat capacity is the amount of energy needed to increase the temperature of one kilogram of a substance by one degree Celsius. A student uses an immersion heater, a thermometer, a joulemeter and an insulated beaker to investigate the specific heat capacity of water.
Model answer (5 marks)
Use insulation around the beaker to minimise heat loss to the surroundings, improving the accuracy of the energy measurement.
Repeat the experiment and calculate a mean temperature reading to improve reliability.
Use a joulemeter (or record the current, voltage and time) to accurately determine the energy supplied to the water.
Stir the water throughout the experiment so that the thermal energy is distributed evenly; this ensures the thermometer gives a representative temperature.
Because temperature is a measure of the average kinetic energy of the particles, an uneven energy distribution would give a misleading reading of the average kinetic energy of all the water particles.
Repeat the experiment and calculate a mean temperature reading to improve reliability.
Use a joulemeter (or record the current, voltage and time) to accurately determine the energy supplied to the water.
Stir the water throughout the experiment so that the thermal energy is distributed evenly; this ensures the thermometer gives a representative temperature.
Because temperature is a measure of the average kinetic energy of the particles, an uneven energy distribution would give a misleading reading of the average kinetic energy of all the water particles.
Examiner tips
- Use the exact terminology: ‘specific heat capacity’, ‘joulemeter’, ‘mean temperature’. Show the logical sequence: insulation → accurate energy → repeat → mean → stir → representative temperature. Mention that stirring prevents temperature gradients and gives a true average.
- common_mistakes
- :
- Failing to mention insulation or the joulemeter. Not explaining why stirring gives a representative temperature. Using vague terms like ‘make it more accurate’ without specifying the method.
Mark scheme (5 marks)
- Use insulation around the beaker to reduce heat loss to the surroundings, improving accuracy of energy measurements
- Repeat the experiment and calculate a mean temperature reading to improve reliability
- Use a joulemeter (or record current and voltage and time) to accurately measure the energy supplied to the water
- Stirring ensures the thermal energy is distributed evenly throughout the water so the thermometer gives a representative temperature reading
- Temperature is a measure of the average kinetic energy of the particles, so an uneven distribution of energy would give a misleading reading of the average kinetic energy of all the water particles
Key terms in this question
specific heat capacity · temperature
Related
- All OCR A-Level Physics A (H556) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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