Phase transitions

Definition

Phase transitions are the processes by which a substance changes from one state of matter (solid, liquid, gas) to another. These changes occur due to variations in temperature and pressure.

5 Must Know Facts For Your Next Test

1. Phase transitions include melting, freezing, vaporization, condensation, sublimation, and deposition.
2. During a phase transition at constant pressure, the temperature of a substance remains constant while it absorbs or releases heat.
3. The amount of heat required for a phase transition is described by latent heat (e.g., latent heat of fusion for melting/freezing).
4. $\Delta G = 0$ during a phase transition at equilibrium where $G$ is Gibbs free energy.
5. Phase diagrams graphically represent the conditions under which different phases occur and coexist at equilibrium.

Review Questions

• What happens to the temperature of a substance during a phase transition at constant pressure?
• How does latent heat differ between melting and vaporization?
• What information can be obtained from a phase diagram?

Related terms

Latent Heat:

The amount of heat required to change the phase of a substance without changing its temperature.

Gibbs Free Energy:

A thermodynamic potential that measures the maximum reversible work obtainable from a thermodynamic system at constant temperature and pressure.

Phase Diagram:

A graphical representation that shows the conditions under which distinct phases occur and coexist at equilibrium.