Practical: investigate the specific heat capacity of a substance
4 marks · NormalIn a school experiment to measure the specific heat capacity of a metal, the calculated value is much higher than the manufacturer's value for that metal.
Suggest two reasons why the result might be higher than expected.
For each reason, explain how it affects the experiment.
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(a) 1. Loss of heat to surroundings (not all energy heats the metal) 2. Inaccurate measurement of temperature change (e.g. if thermometer not placed correctly)
(b) 1. If heat escapes to the surroundings, the temperature rise for the same energy input is less—so calculated c is larger. 2. If the final temperature is measured before the whole block is evenly heated, Δθ may be underestimated, raising calculated value of c.
Common mistakes: Not explaining how errors lead to a larger value
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Marking points
B1 (a) · 1 mark · Identifies any valid cause of error (e.g., heat loss, temperature not evenly distributed) – up to 2 for both.
B2 (a) · 1 mark · Second valid reason identified.
E1 (b) · 1 mark · Clearly explains how first identified error increases the result.
E2 (b) · 1 mark · Clearly explains how second identified error increases the result.
Worked solution
a) Two reasons: 1. Heat is lost to the air or the apparatus during the experiment, so not all energy heats the metal. 2. Temperature of the metal may not be measured accurately, e.g. thermometer not in good thermal contact, leading to an underestimated rise.
b) Error 1 effect: Since less heat goes into raising the metal's temperature, Δθ is smaller than expected, which makes calculated c (energy/mΔθ) appear larger. Error 2 effect: If the measured temperature does not reflect the true increase across the whole block, Δθ is too small, so c is overestimated.