Phase Changes A change from one state of matter (solid, liquid, gas) to another. Physical change because appearance is changed, not chemical make-up; reversible.

Phase Changes

• A change from one state of matter (solid, liquid, gas) to another.

• Physical change because appearance is changed, not chemical make-up; reversible.

• Heat energy is either absorbed (molecules speed up) or released (molecules slow down)

• Ex. Melting: Ice to water; heat absorbed

Types of Phase Changes

Melting

• Phase change from a solid to a liquid

• Molecules speed up, move farther apart, and absorb heat energy

Freezing

• Phase Change from a liquid to a solid

• Molecule slow down, move closer together and release heat energy.

Evaporation

• Phase change from a liquid to a gas (occurs at the boiling point)

• Molecules speed up, move farther apart, and absorb heat energy.

Condensation

• Phase change from a gas to a liquid.

• Molecules slow down, move closer together and release heat energy.

Sublimation

• Phase change from a solid to a gas.

• Molecules speed up, move farther apart, and absorb heat energy.

Deposition

• Phase change from a gas to a solid.

• Molecules slow down, move closer together and release heat energy.

• Vapor in air turns directly into frost on a windshield