Latent Heat

• Meaning ‘hidden heat’
• Energy involved in a state change
• If one adds heat at a constant rate to a solid will see a temperature/time graph as:

• A liquid losing heat at a constant rate will fall in temperature as:

• In each case the temperature stays constant while the change of state takes place. All the same, there is still energy transfer to or from the particles
• The quantity of energy transferred during the state change depends on what the substance is and its state

Specific Latent Heat

• energy involved in the state change of a kilogram of substance
• Unit J/kg
• ice/water: 336kJ/kg; water/steam: 2270kJ/kg