AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Temperature changes in a system and specific heat capacity: If the temperature of the system increases:
When a system is heated and no change of state occurs, the energy transferred raises the average kinetic energy of the particles, so the temperature increases.
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
When a system is heated and no change of state occurs, the energy transferred raises the average kinetic energy of the particles, so the temperature increases. The temperature rise depends on three things: the mass of the material, the specific heat capacity of the material, and the energy transferred. Specific heat capacity is the energy needed to raise the temperature of 1 kg of a material by 1 °C. The relationship is ΔE = m c Δθ, where ΔE is energy transferred in joules, m is mass in kilograms, c is specific heat capacity in J/kg °C and Δθ is the temperature change in °C. For example, heating 2 kg of water (c = 4200 J/kg °C) by 10 °C needs ΔE = 2 × 4200 × 10 = 84 000 J.
What earns the marks
- A temperature increase means the average kinetic energy of the particles has increased.
- The energy transferred to raise temperature is given by ΔE = m c Δθ.
- Specific heat capacity is the energy required to raise 1 kg of a substance by 1 °C.
- Mass, specific heat capacity and temperature change all affect the energy transferred.
- Rearranging the equation allows calculation of c or Δθ when the other values are known.
- The equation applies when the substance is heated without changing state.
Common mistakes and how to put them right
Using grams instead of kilograms in ΔE = m c Δθ.
Put it right by converting mass to kg before substituting.
Mixing up specific heat capacity with specific latent heat.
Put it right by noting that c applies to temperature change, while latent heat applies to change of state.
Using the final temperature instead of the temperature change for Δθ.
Put it right by subtracting the initial temperature from the final temperature to find the change.
Exam tips
- Write the equation ΔE = m c Δθ, substitute values with units, then calculate and give the unit J.
- If asked to find c or Δθ, rearrange the equation before substituting numbers to reduce errors.
- Check whether the question involves a temperature change or a change of state before choosing c or latent heat.
Try the lesson
The start of the Temperature changes in a system and specific heat capacity: If the temperature of the system increases: lesson, made from checked teaching notes for this specification point.
Have a go first
A beaker of water is warmed on a bench. If the temperature of the system increases, what happens to the thermal energy stored by the water?
Listen
When a system is heated and no change of state occurs, the energy transferred raises the average kinetic energy of the particles, so the temperature increases. The temperature rise depends on three things: the mass of the material, the specific heat capacity of the material, and the energy transferred. Specific heat capacity is the energy needed to raise the temperature of 1 kg of a material by 1 °C. The relationship is ΔE = m c Δθ, where ΔE is energy transferred in joules, m is mass in kilograms, c is specific heat capacity in J/kg °C and Δθ is the temperature change in °C. For example, heating 2 kg of water (c = 4200 J/kg °C) by 10 °C needs ΔE = 2 × 4200 × 10 = 84 000 J. A strong answer earns marks for these points. A temperature increase means the average kinetic energy of the particles has increased. The energy transferred to raise temperature is given by ΔE = m c Δθ. Specific heat capacity is the energy required to raise 1 kg of a substance by 1 °C. Mass, specific heat capacity and temperature change all affect the energy transferred. A common slip: Using grams instead of kilograms in ΔE = m c Δθ. Instead, converting mass to kg before substituting. Exam tip: Write the equation ΔE = m c Δθ, substitute values with units, then calculate and give the unit J.
Key words
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Specific heat capacity
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ΔE = m c Δθ
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Temperature increase
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See every definition
- Specific heat capacity
- The energy needed to raise the temperature of 1 kg of a material by 1 °C.
- ΔE = m c Δθ
- The relationship where ΔE is energy transferred in joules, m is mass in kilograms, c is specific heat capacity in J/kg °C and Δθ is the temperature change in °C.
- Temperature increase
- A rise that means the average kinetic energy of the particles has increased.
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