States of Matter and Phase Changes

• Matter can change from one state to another.
• Energy in the form of heat is involved when matter changes state.

Solid to Liquid: Melting

• Melting changes a solid into a liquid.
• Solids melt when they absorb heat
• An icicle melts when it absorbs heat from the air around it.
• An ice cube melts in a glass of water because cold water is warmer than an ice cube, so the ice cube can absorb heat from the water.

Liquid to Gas: Evaporation

• Evaporation changes a liquid into a gas.
• Liquids evaporate when they absorb heat.
• Steam coming out of a boiling kettle is water that has turned into a gas by evaporating.

Gas to Liquid: Condensation

• Condensation changes a gas into a liquid.
• Gases condense when they release heat.
• A mirror in a bathroom may look misty or cloudy after a shower, which is caused by condensation.
• Some of the hot water from the shower evaporates, becoming water vapor (steam) in the air.
• The water vapor releases heat when it touches the cooler mirror.
• The vapor condenses into drops of water to cloud the mirror.

Liquid to Solid: Freezing

• Freezing changes a liquid into a solid.
• Water freezes when the air around it is cold enough as cold air makes water release heat.
• A refrigerator's air is not cold enough to make water release enough heat to turn into ice.
• The process of matter changing from a liquid to a solid is sometimes called solidification.