AQA · GCSE · Physics

    Course version: 8463 · Version from Sept 2016

    The amount of energy stored in or released from a system as its…

    Full specification wording

    Energy changes in systems: The amount of energy stored in or released from a system as its temperature changes can be calculated using the equation:

    Heat a substance and its particles gain kinetic energy, so its internal store rises and its temperature climbs.

    Checked against the AQA 8463 specification (opens in a new tab) on .

    • Point 1 of 2
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    Heat a substance and its particles gain kinetic energy, so its internal store rises and its temperature climbs. How much energy that takes depends on three things: how much substance there is, how many degrees you want, and what the substance is made of. Those three appear in ΔE = m c Δθ. Water has a specific heat capacity of 4200 J/kg °C, so it takes 4200 J to warm one kilogram by one degree; the same energy would raise a kilogram of copper, at 385 J/kg °C, by about 11 °C. The equation works both ways, so a cooling object releases the same energy that heating it would need, which is why a high specific heat capacity material makes a good store and a good coolant.

    What earns the marks

    • Selecting ΔE = m c Δθ and identifying the three quantities from the question.
    • Using the temperature change rather than the final temperature.
    • A correct substitution with mass in kilograms.
    • The energy in joules, or for the correct rearrangement when c or Δθ is the unknown.

    Common mistakes and how to put them right

    • Putting the final temperature into the equation instead of the difference between start and finish.

    • Using grams for mass with a specific heat capacity quoted per kilogram.

    • Assuming a material that heats quickly must be storing more energy, when it has a low specific heat capacity.

    • Using ΔE = m c Δθ for the part of a process where the substance is changing state, when that part needs the specific latent heat equation E = m L instead.

    Exam tips

    • Write Δθ as final minus initial in its own line before substituting, so the sign and size are both clear.
    • A temperature change of 1 °C and of 1 K are the same size, so no conversion is needed.
    • If the answer comes out in the millions, check whether the mass should have been in kilograms.

    Try the lesson

    The start of the Energy changes in systems: The amount of energy stored in or released from a system as its temperature changes can be calculated using the equation: lesson, made from checked teaching notes for this specification point.

    Have a go first

    A 2 kg block of aluminium is heated and its temperature rises by 5 °C. The specific heat capacity of aluminium is 900 J/kg °C. Which calculation gives the change in thermal energy of the block in joules?

    Listen

    Heat a substance and its particles gain kinetic energy, so its internal store rises and its temperature climbs. How much energy that takes depends on three things: how much substance there is, how many degrees you want, and what the substance is made of. Those three appear in ΔE = m c Δθ. Water has a specific heat capacity of 4200 J/kg °C, so it takes 4200 J to warm one kilogram by one degree; the same energy would raise a kilogram of copper, at 385 J/kg °C, by about 11 °C. The equation works both ways, so a cooling object releases the same energy that heating it would need, which is why a high specific heat capacity material makes a good store and a good coolant. A strong answer earns marks for these points. selecting ΔE = m c Δθ and identifying the three quantities from the question. using the temperature change rather than the final temperature. a correct substitution with mass in kilograms. the energy in joules, or for the correct rearrangement when c or Δθ is the unknown. Exam tip: Write Δθ as final minus initial in its own line before substituting, so the sign and size are both clear.

    See it

    A top-down flowchart. The first box reads 'Energy supplied to a system' and points down to 'Particles gain kinetic energy', which points down to 'Internal store rises', which points down to 'Temperature climbs'. From 'Temperature climbs' three arrows lead to three boxes side by side: 'Energy stored depends on: amount of substance', 'Energy stored depends on: temperature change wanted' and 'Energy stored depends on: what the substance is made of'. All three of these point down to a single box reading 'ΔE = m c Δθ', which points down to a final box reading 'Cooling releases the same energy that heating would need'.
    It shows how heating raises a system's internal store and temperature, the three factors that set how much energy is stored, and how they combine in ΔE = m c Δθ, with cooling releasing the same energy.

    Key words

    Say what each word means before you turn the card.

    internal energy

    Try answering aloud or in your head before turning the card.

    specific heat capacity

    Try answering aloud or in your head before turning the card.

    temperature change

    Try answering aloud or in your head before turning the card.

    energy released on cooling

    Try answering aloud or in your head before turning the card.

    See every definition
    internal energy
    The energy stored in a system, which rises as its particles gain kinetic energy when the substance is heated.
    specific heat capacity
    The energy needed to warm one kilogram of a substance by one degree, quoted per kilogram.
    temperature change
    The difference between the start and finish temperatures, written as final minus initial and used rather than the final temperature.
    energy released on cooling
    The same energy that heating the object would need, because the equation works both ways.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. The first box reads 'Energy supplied to a system' and points down to 'Particles gain kinetic energy', which points down to 'Internal store rises', which points down to 'Temperature climbs'. From 'Temperature climbs' three arrows lead to three boxes side by side: 'Energy stored depends on: amount of substance', 'Energy stored depends on: temperature change wanted' and 'Energy stored depends on: what the substance is made of'. All three of these point down to a single box reading 'ΔE = m c Δθ', which points down to a final box reading 'Cooling releases the same energy that heating would need'.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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