# What are some examples of changes of state?

May 23, 2015

Phase changes include vaporization, condensation, melting, freezing, sublimation, and deposition.

Evaporation, a type of vaporization, occurs when particles of a liquid reach a high enough energy to leave the surface of the liquid and change into the gas state. An example of evaporation is a puddle of water drying out. It dries out because the molecules of water evaporate into the atmosphere.

Boiling is a type of rapid vaporization that occurs when a the particles of a liquid are heated to its boiling point. Large bubbles of gas form throughout the the liquid and move to the surface, leaving the liquid. Steam is the gaseous water molecules that form above boiling water.

Condensation occurs when the particles in a gas cool enough (lose energy) to change to the liquid state. An example of condensation is when a glass of ice water forms water droplets on the outside. The molecules of water vapor next to the glass cool and condense into liquid water.

Melting occurs when a solid is heated until its particles reach a high enough energy to reach its melting point, changing it into the liquid state. An example of melting is an ice cube turning into liquid water when you set it on a surface, or hold it in your hand.

Freezing occurs when a liquid is cooled until its particles reach a low enough energy to reach its freezing point, changing it into the solid state. This occurs to liquid water when it is placed in a freezer. (Actually, anything that is solid is frozen!)

Sublimation occurs when a solid changes into the gas state without passing through the liquid state. Iodine is an example of a substance that sublimes, as well as solid carbon dioxide (dry ice), snow, and ice.

Deposition occurs when a gas changes into a solid without passing through the liquid state. Examples of deposition include the formation of snow in clouds, formation of frost on windows and the ground, and discharging a ${\text{CO}}_{2}$ fire extinguisher.