Latent Heat
Physics: AQA GCSE Higher, topic 3.2.8
Latent Heat
Latent heat is the energy that is transferred to a substance without the substance's temperature changing. This happens when a substance is changing state.
Where does latent heat go?
- When a substance changes state, this energy is absorbed (used) to create or weaken bonds, rather than transfer kinetic energy to a substance’s particles.
Why isn't latent heat measured?
- If we measure energy using the change in temperature, this energy transfer will not be measured.
- The energy is transferred without the temperature changing.
Specific latent heat
- Specific latent heat is the latent heat per 1kg of mass.
- It is a way to standardise across objects that have different masses.
Latent heat's other names
- When a solid becomes a liquid or a liquid becomes a solid, this hidden energy is called the latent heat of fusion.
- When a gas becomes a liquid, or a liquid becomes a gas, this hidden energy is called the latent heat of vaporisation.
Change in state
- The equation for calculating the energy change experienced by a substance when it changes state is:
- Energy = mass × specific latent heat
Test yourself on Latent Heat
How can you detect latent heat?
What happens to the energy supplied during a change of state at both the melting and boiling points?