9702 · 14.3
Specific heat capacity and specific latent heat flashcards
Revision flashcards for Cambridge 9702 Specific heat capacity and specific latent heat (syllabus 14.3). Flip, recall, then mark a real past-paper question.
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Define specific heat capacity.
The thermal energy needed to raise the temperature of 1 kg of a substance by 1 K (or 1 °C) without changing its state.
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What is the formula used to calculate the heat required to change a substance's temperature?
$Q = mc\Delta T$, where $Q$ is heat energy, $m$ is mass, $c$ is specific heat capacity, and $\Delta T$ is temperature change.
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What is the SI unit for specific heat capacity?
Joules per kilogram per Kelvin (J kg⁻¹ K⁻¹).
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Define specific latent heat.
The thermal energy needed to change the state of 1 kg of a substance without changing its temperature.
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What is the formula for calculating heat energy during a state change?
$Q = mL$, where $Q$ is heat energy, $m$ is mass, and $L$ is specific latent heat.
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What happens to the energy supplied to a substance during a phase change?
The energy is used to increase the potential energy of the particles by breaking intermolecular bonds, rather than increasing their kinetic energy.
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Why is the specific latent heat of vaporisation usually greater than the specific latent heat of fusion for the same substance?
Converting a liquid to a gas requires breaking significantly more intermolecular bonds than converting a solid to a liquid.
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How does evaporation cause cooling?
High-energy particles escape from the liquid surface, reducing the average kinetic energy and temperature of the remaining liquid.
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During an experiment to find specific heat capacity, why might the calculated value be higher than the actual value?
Due to unavoidable energy losses from the heated substance to the surroundings.
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How can accuracy be improved in experimental determinations of specific heat or latent heat?
By using insulation, minimising heat losses, and reducing electrical resistance in heating wires.
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What is the SI unit for specific latent heat?
Joules per kilogram (J kg⁻¹).