Latent Heat

Conceptual Questions

• Under normal conditions (atmospheric pressure) what are the temperatures at which you can have liquid water?

• What are the temperatures that you can have ice?

• What range of temperatures for ice water?

• What range of temperatures for boiling water?

Learning Objectives

• Understand and calculate heat capacity to find energy needed to make phase changes.

• Describe phase changes like freezing, melting, evaporation, and condensation.

Latent heat of fusion

• How much energy does it take to freeze a gram of water?

• What is the temperature of the water before and after freezing?

Latent heat of vaporization

• How much energy does it take to boil a gram of water?

• What is the temperature of the water before and after boiling?

Heat capacities

Water	4.18 J per g per Kelvin
Ice	2.11 J per g per Kelvin
Steam	2.00 J per g per Kelvin

Phase change

During a phase change, the temperature stays the same.

Latent heat

The amount of energy added or removed from material to change phase.

Latent heats

Evaporation	2.26 kJ per gram
Melting	0.334 kJ per gram

Relation to enthalpy

You may have seen these quantities referred to as enthalpy of fusion or the enthalpy of vaporization.