OCR · GCSE · Physics
Course version: J249 · Version from Sept 2018
Define the term specific heat capacity and distinguish between it and the…
Full specification wording
Changes of state: define the term specific heat capacity and distinguish between it and the term specific latent heat (to include: specific latent heat of fusion and specific latent heat of vaporisation)
Specific heat capacity is the energy needed to raise the temperature of 1 kg of a substance by 1 °C (equivalently 1 K), with no change of state.
Checked against the OCR J249 specification (opens in a new tab) on .
- Point 6 of 8
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Specific heat capacity is the energy needed to raise the temperature of 1 kg of a substance by 1 °C (equivalently 1 K), with no change of state. For example, water needs about 4200 J to warm 1 kg by 1 °C, so its value is roughly 4200 J/(kg °C). Specific latent heat is different: it is the energy needed to change the state of 1 kg of a substance with no change in temperature. Melting or freezing uses the specific latent heat of fusion; boiling or condensing uses the specific latent heat of vaporisation. So a temperature change signals specific heat capacity, while a state change at constant temperature signals specific latent heat.
What earns the marks
- States that specific heat capacity is the energy needed to raise the temperature of 1 kg of a substance by 1 °C without a change of state.
- States that specific latent heat is the energy needed to change the state of 1 kg of a substance with no change in temperature.
- Links specific latent heat of fusion to melting or freezing and specific latent heat of vaporisation to boiling or condensing.
- Distinguishes the two by noting that specific heat capacity involves a temperature change while specific latent heat involves a change of state at constant temperature.
Common mistakes and how to put them right
Confuses the two quantities by describing specific heat capacity as the energy for a change of state.
Put it right by tying specific heat capacity to a 1 °C temperature rise of 1 kg.
Omits the per-kilogram basis and treats the values as totals for any amount.
Put it right by stating that both quantities are defined per 1 kg.
Attaches the latent heat terms to the wrong changes by swapping fusion and vaporisation.
Put it right by linking fusion to melting or freezing and vaporisation to boiling or condensing.
Exam tips
- Read the question stem for the words 'temperature change' or 'change of state' before choosing, because that phrase decides which quantity is meant.
- Check that any definition you select includes both '1 kg' and the relevant condition (1 °C rise or change of state).
- Eliminate options that give a total energy rather than an energy per kilogram, since both definitions are per unit mass.
Try the lesson
The start of the Changes of state: define the term specific heat capacity and distinguish between it and the term specific latent heat (to include: specific latent heat of fusion and specific latent heat of vaporisation) lesson, made from checked teaching notes for this specification point.
Have a go first
Which quantity is measured by the specific heat capacity of a material?
Listen
Specific heat capacity is the energy needed to raise the temperature of 1 kg of a substance by 1 °C (equivalently 1 K), with no change of state. For example, water needs about 4200 J to warm 1 kg by 1 °C, so its value is roughly 4200 J/(kg °C). Specific latent heat is different: it is the energy needed to change the state of 1 kg of a substance with no change in temperature. Melting or freezing uses the specific latent heat of fusion; boiling or condensing uses the specific latent heat of vaporisation. So a temperature change signals specific heat capacity, while a state change at constant temperature signals specific latent heat. A strong answer earns marks for these points. States that specific heat capacity is the energy needed to raise the temperature of 1 kg of a substance by 1 °C without a change of state. States that specific latent heat is the energy needed to change the state of 1 kg of a substance with no change in temperature. Links specific latent heat of fusion to melting or freezing and specific latent heat of vaporisation to boiling or condensing. Distinguishes the two by noting that specific heat capacity involves a temperature change while specific latent heat involves a change of state at constant temperature. A common slip: Confuses the two quantities by describing specific heat capacity as the energy for a change of state. Instead, tying specific heat capacity to a 1 °C temperature rise of 1 kg. Exam tip: Read the question stem for the words 'temperature change' or 'change of state' before choosing, because that phrase decides which quantity is meant.
Key words
Say what each word means before you turn the card.
Specific heat capacity
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Specific latent heat
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Specific latent heat of fusion
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Specific latent heat of vaporisation
Try answering aloud or in your head before turning the card.
See every definition
- Specific heat capacity
- The energy needed to raise the temperature of 1 kg of a substance by 1 °C without a change of state.
- Specific latent heat
- The energy needed to change the state of 1 kg of a substance with no change in temperature.
- Specific latent heat of fusion
- The energy needed to change the state of 1 kg of a substance by melting or freezing, with no change in temperature.
- Specific latent heat of vaporisation
- The energy needed to change the state of 1 kg of a substance by boiling or condensing, with no change in temperature.
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