4.3.2.3 - Changes of state and specific latent heat

In reference to energy, what happens when a change of state occurs?

The energy supplied changes the energy stored (internal energy) but not the temperature

So when a substance is melting / boiling, what is the energy you're inuputting being used for?

When a substance Is melting or boiling, the energy you’re inputting is used for breaking bonds between particles (rather than raising temperatures)

How does this look on heating / cooling graphs?

This creates flat spots on the heating graph, where engirt is being transferred by heating but not being used to change the temperature

Explain what happens when a substance is condensing or freezing in terms of temperature?

When a substance is condensing or freezing, bonds are forming between particles which releases energy.

This means the internal energy decreases, but the temperature does not go down until all the substance has turned into a liquid / solid

What is the ‘specific latent heat’ of a substance?

The specific latent heat of a substance Is the amount of energy required to change the state of 1 kg of the substance with no change in temperature.

(The energy needed for a substance to change state)

Give the equation for calculating the energy needed / released for a change in state.

Energy needed / released for a change of state = mass x specific latent heat

Give the units for all.

E = mL

E = in joules

m = in kg

L = J/Kg

What is the specific latent heat of fusion.

Specific latent heat - energy needed / released for a substance too change from a solid to a liquid or vice versa

What is the specific latent heat of vaporisation.

Specific latent heat - energy needed / released for a substance too change from a liquid to a gas / vapour or vice versa