Specific Heat Capacity
Understand Specific Heat Capacity for GCSE Physics with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Specific heat capacity is the energy needed to raise the temperature of 1 kg of a substance by 1 °C, linked by E = mcΔθ.
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Topic overview
The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius. This is a required practical.
The equation is change in thermal energy = mass × specific heat capacity × temperature change, or ΔE = mcΔθ. Water has a high specific heat capacity of about 4200 J/kg°C, which is why it is used in heating systems and why coastal areas have milder climates.
In the practical, a block of known mass is heated with an immersion heater while a joulemeter measures the energy supplied and a thermometer measures the temperature rise. Insulating the block reduces energy loss to the surroundings, which would otherwise make the measured value too high.
Revision notes
The equation
Change in thermal energy = mass × specific heat capacity × temperature change, ΔE = mcΔθ.
Mass in kilograms, specific heat capacity in J/kg°C, temperature change in degrees Celsius, energy in joules. Note it is the temperature CHANGE, not the final temperature.
What specific heat capacity means
It is the energy needed to raise the temperature of 1 kg of a substance by 1 °C.
A high value means a lot of energy is needed for a small temperature rise. Water's value of about 4200 J/kg°C is unusually high, which is why it is used in central heating systems.
The practical
Heat a block of known mass with an immersion heater, measuring the energy supplied with a joulemeter and the temperature with a thermometer.
Insulate the block to reduce energy transfer to the surroundings, which would otherwise mean more energy was needed than the theoretical value, giving too high a result.
Key points
- Specific heat capacity is energy per kg per °C.
- ΔE = mass × specific heat capacity × temperature change.
- Water's value is about 4200 J/kg°C.
- Use the temperature change, not the final temperature.
- Insulate the block to reduce energy loss.
- Energy loss makes the measured value too high.
Worked examples
Example 1
Calculate the energy needed to raise the temperature of 2 kg of water by 30 °C. Specific heat capacity of water = 4200 J/kg°C. [3 marks]
Model answer
Energy = mass × specific heat capacity × temperature change = 2 × 4200 × 30 (1 mark). 2 × 4200 = 8400 (1 mark). 8400 × 30 = 252 000 J (1 mark).
Example 2
Define specific heat capacity. [2 marks]
Model answer
The specific heat capacity is the amount of energy required to raise the temperature of one kilogram of a substance (1 mark) by one degree Celsius (1 mark).
Example 3
Explain why the block should be insulated during the experiment. [2 marks]
Model answer
Insulation reduces the energy transferred to the surroundings (1 mark), so the measured value of specific heat capacity is closer to the true value rather than being too high (1 mark).
Common mistakes
Using the final temperature instead of the change.
The equation needs the temperature CHANGE, so subtract the starting temperature.
Using grams instead of kilograms.
Mass must be in kilograms.
Saying insulation makes the value too low.
Energy loss means more energy is supplied than needed, so the calculated value is too HIGH.
Confusing specific heat capacity with specific latent heat.
Specific heat capacity changes temperature; latent heat changes state.
Exam tips
- Calculate the temperature change before substituting.
- Use kilograms and degrees Celsius.
- Explain insulation in terms of energy loss to the surroundings.
- Remember water's value of about 4200 J/kg°C.
Key terms
- Specific heat capacity
- Energy needed to raise 1 kg by 1 °C.
- Temperature change
- The difference between final and starting temperature.
- Joulemeter
- Apparatus measuring the energy supplied.
- Immersion heater
- A heater placed inside the block being heated.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.