Changes of State

Melting

Freezing Vapor

izatio

n

Conde

nsati

on

Change of State• A phase change is when a substance converts from one

state to another.– Ex. Solid to a liquid

• All changes of state are ____________changes.• During a change of state, the _________of a substance changes.

– Particles in liquid water move faster than the particles of ice, therefore liquid water has more energy than ice.

Melting: Solids to Liquids

• Melting is the change of state from a solid to a liquid.

• Melting Point is the temperature at which a substance changes from a solid to a liquid.

• Melting is an endothermic change.– Endothermic Change means that energy is

______________(enters).

Freezing: Liquids to Solids

• ___________is the change of state from a liquid to a solid.

• Freezing is an ______________________.

– Exothermic changes means that energy is ______________(exits).

Vaporization: Liquids to Gases

• _______________is the change of state from a liquid to a gas.

• ___________is vaporization that occurs throughout a liquid. A liquid boils at its boiling point.

• ___________is vaporization that occurs at the ___________of a liquid below its boiling point.

• Vaporization is _______________.

Condensation: Gases to Liquids

• _____________is the change of state from a gas to a liquid.

• Gas becomes a liquid at its condensation point.

• The _______________of a substance is the same as its boiling point.

• Condensation is _______________.

Sublimation: Solids Directly to Gas• __________________is the change of state from a solid

directly to a gas. There is no liquid state.

• Dry ice is an example of a solid changing straight to a gas.

• Sublimation is _______________.

Summarizing the Changes of State

Change of State Direction Endothermic or exothermic

Example

____________ solid liquid endothermic

Freezing liquid solid ______________ Liquid water freezes into ice at 0oC

____________ liquid gas ______________ Liquid water vaporizes into steam at 100oC

Condensation gas liquid exothermic

____________ solid gas endothermic Solid dry ice sublimes into a gas at –78oC

Heating Curve of Water

Time

Tem

pera

ture

(o C

)

0

100 Boiling Point

Melting Point

Temperature remains at the melting point until all of the solid has melted.

Temperature remains at the boiling point until all of the solid has vaporized.