AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Change in thermal energy = mass × speci f ic heat capacity × temperature…
Full specification wording
Energy changes in systems: change in thermal energy = mass × speci f ic heat capacity × temperature change ∆E = m c ∆ θ change in thermal energy, ∆E, in joules, J mass, m, in kilograms, kg specific heat capacity, c, in joules per kilogram per degree Celsius, J/kg °C temperature change, ∆θ, in degrees Celsius, °C 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.
Specific heat capacity, c, is the energy needed to raise the temperature of one kilogram of a substance by one degree Celsius, measured in J/kg °C. In the equation ΔE = m c Δθ, mass is in…
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 2 of 2
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Specific heat capacity, c, is the energy needed to raise the temperature of one kilogram of a substance by one degree Celsius, measured in J/kg °C. In the equation ΔE = m c Δθ, mass is in kilograms, Δθ is the temperature change in degrees Celsius and ΔE comes out in joules. To measure c for water, heat a known mass in an insulated container with an immersed electric heater, record the energy from a joulemeter, or from E = P t, and measure the temperature rise with a thermometer. Then c = ΔE ÷ (m Δθ). The value always comes out too high because some energy heats the container and escapes to the surroundings rather than the water. Insulating the container, fitting a lid and starting the water below room temperature all reduce that error.
What earns the marks
- Measuring the mass of the substance with a balance and recording the starting temperature.
- Measuring the energy supplied using a joulemeter or from power multiplied by time.
- Measuring the temperature rise after a stated time with a thermometer.
- Substituting into c = ΔE ÷ (m Δθ) and giving the unit J/kg °C.
- Insulating the container and identifying energy transfer to the surroundings as a source of error.
Common mistakes and how to put them right
Recording only the final temperature, leaving no way to work out Δθ.
Quoting the unit as J/kg or as J/°C rather than J/kg °C.
Assuming all the electrical energy reaches the substance, so ignoring the container and the surroundings.
Starting the timer before the heater is switched on, which inflates the energy supplied.
Exam tips
- In a six-mark method, give the measuring instrument for every quantity and the equation you will use at the end.
- Name insulation and a lid as controls, then say they reduce energy transfer to the surroundings.
- State the direction of any error: heating the container makes the measured specific heat capacity too high.
Try the lesson
The start of the Energy changes in systems: change in thermal energy = mass × speci f ic heat capacity × temperature change ∆E = m c ∆ θ change in thermal energy, ∆E, in joules, J mass, m, in kilograms, kg specific heat capacity, c, in joules per kilogram per degree Celsius, J/kg °C temperature change, ∆θ, in degrees Celsius, °C 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. lesson, made from checked teaching notes for this specification point.
Have a go first
Which statement defines the specific heat capacity of a substance?
Listen
Specific heat capacity, c, is the energy needed to raise the temperature of one kilogram of a substance by one degree Celsius, measured in J/kg °C. In the equation ΔE = m c Δθ, mass is in kilograms, Δθ is the temperature change in degrees Celsius and ΔE comes out in joules. To measure c for water, heat a known mass in an insulated container with an immersed electric heater, record the energy from a joulemeter, or from E = P t, and measure the temperature rise with a thermometer. Then c = ΔE ÷ (m Δθ). The value always comes out too high because some energy heats the container and escapes to the surroundings rather than the water. Insulating the container, fitting a lid and starting the water below room temperature all reduce that error. A strong answer earns marks for these points. measuring the mass of the substance with a balance and recording the starting temperature. measuring the energy supplied using a joulemeter or from power multiplied by time. measuring the temperature rise after a stated time with a thermometer. substituting into c = ΔE ÷ (m Δθ) and giving the unit J/kg °C. Exam tip: In a six-mark method, give the measuring instrument for every quantity and the equation you will use at the end.
Key words
Say what each word means before you turn the card.
specific heat capacity
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units J/kg °C
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temperature rise
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sources of error
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See every definition
- specific heat capacity
- The amount of energy required to raise the temperature of one kilogram of a substance by one degree Celsius.
- units J/kg °C
- The units of specific heat capacity, joules per kilogram per degree Celsius.
- temperature rise
- The temperature change, ∆θ, in degrees Celsius, measured with a thermometer after a stated time.
- sources of error
- Energy transferred to the container and the surroundings, which makes the experimental value too high.
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Test your understanding of Energy changes in systems: change in thermal energy = mass × speci f ic heat capacity × temperature change ∆E = m c ∆ θ change in thermal energy, ∆E, in joules, J mass, m, in kilograms, kg specific heat capacity, c, in joules per kilogram per degree Celsius, J/kg °C temperature change, ∆θ, in degrees Celsius, °C 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.
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