Section 2.2Section 2.2

CHANGES OF STATE ARE CHANGES OF STATE ARE PHYSICAL CHANGESPHYSICAL CHANGES

II. Solids can become liquids, II. Solids can become liquids, and liquids can become and liquids can become solidssolids

1)1) Examples of solids that can Examples of solids that can change to liquidschange to liquids

a)a) Ice melts into waterIce melts into water

b)b) Others???Others???

A. MeltingA. Melting1)1) Melting is the process of Melting is the process of a solid a solid

becoming a liquidbecoming a liquid2)2) Different solids melt at different Different solids melt at different

temperaturestemperatures 3)3) Energy is Energy is GAINEDGAINED making the particles making the particles

move move FASTERFASTER4)4) Melting point is Melting point is the lowest temperature the lowest temperature

at which a substanceat which a substance melts melts 5)5) Substances with a well-defined melting Substances with a well-defined melting

point point have an orderly structurehave an orderly structure

B. FreezingB. Freezing1)1) Freezing is the process of Freezing is the process of a liquid a liquid

becoming a solidbecoming a solid

2)2) many substances are “frozen” at room many substances are “frozen” at room temperaturetemperature

3)3) Energy is Energy is LOSTLOST making the particles making the particles move move SLOWERSLOWER

4)4) Freezing point is Freezing point is the temp. at which a the temp. at which a liquid becomes a solidliquid becomes a solid

5)5) Freezing point of a substance equals Freezing point of a substance equals the the melting pointmelting point of that same of that same substancesubstance

A. EvaporationA. Evaporation1)1) Evaporation is the process of Evaporation is the process of a a

liquid becoming a gasliquid becoming a gas

2)2) Usually occurs at the surfaceUsually occurs at the surface

3)3) Solids can lose particles at the Solids can lose particles at the surface, similar to liquids, by the surface, similar to liquids, by the process of process of sublimationsublimation

4)4) Energy is Energy is GAINEDGAINED making the making the particles move particles move FASTERFASTER

B. BoilingB. Boiling1)1) Boiling is the process of Boiling is the process of changing changing

a liquid to a gasa liquid to a gas by producing by producing bubblesbubbles which contain which contain dissolved dissolved airair

2)2) Can occur only when a certain Can occur only when a certain temp. has been reached which is temp. has been reached which is called the called the boiling pointboiling point

3)3) The boiling point of water at The boiling point of water at higher elevations is higher elevations is lowerlower because because of lower air pressureof lower air pressure

B. Boiling (continued)B. Boiling (continued)

4)4) Different substances have different Different substances have different boiling pointsboiling points

a) Helium boils at a) Helium boils at -270-270°C (-454°F)°C (-454°F)

b) Aluminum boils at b) Aluminum boils at 25192519°C (4566°F)°C (4566°F)

5)5) Energy is Energy is GAINEDGAINED making the making the particles move particles move FASTERFASTER

C. CondensationC. Condensation

1)1) Condensation is process by which Condensation is process by which a a gas becomes a liquidgas becomes a liquid

2)2) Energy is Energy is LOSTLOST making the making the particles move particles move SLOWERSLOWER

3)3) Like evaporation, condensation Like evaporation, condensation occurs over a wide range of occurs over a wide range of temperaturestemperatures