Chapter 3, Section 3Chapter 3, Section 3

Changes in StateChanges in State

Change of StateChange of State

Change of State: Change of State: change of a change of a substance from one physical form to substance from one physical form to anotheranother

Change of state happens by: Change of state happens by: – removing or adding energy!removing or adding energy!

Which changes the particle speed, the Which changes the particle speed, the temperature, and finally the state changes!temperature, and finally the state changes!

ENDO vs. EXOENDO vs. EXO EndothermicEndothermic: Add Energy: Add Energy

– To add energy, increase the To add energy, increase the temperature, the particle movement temperature, the particle movement increasesincreases

ExothermicExothermic: Remove Energy: Remove Energy– To remove energy, decrease the To remove energy, decrease the

temperature, the particle movement temperature, the particle movement decreasesdecreases

EX: EX: – Boiling Water. ENDO or EXOBoiling Water. ENDO or EXO– Freeze Water. ENDO or EXOFreeze Water. ENDO or EXO

Solid to Liquid?Solid to Liquid?

MeltingMelting

Endothermic ProcessEndothermic Process– Adds energyAdds energy– Temperature increasesTemperature increases– Particles move fasterParticles move faster– When a certain temperature is reached, When a certain temperature is reached,

the solid will melt (melting point)the solid will melt (melting point)

Liquid to Solid?Liquid to Solid?

FreezingFreezing

Exothermic ProcessExothermic Process– Removes energyRemoves energy– Temperature decreasesTemperature decreases– Particles slow downParticles slow down– When the liquid reaches a certain When the liquid reaches a certain

temperature, the liquid will become a temperature, the liquid will become a solid (freezing point)solid (freezing point)

Freezing is the reverse of meltingFreezing is the reverse of melting

Liquid to Gas?Liquid to Gas?

EvaporationEvaporation

Occurs at the surfaceOccurs at the surface Endothermic ProcessEndothermic Process

– Adds energyAdds energy– Temperature increasesTemperature increases– As the surface reaches a certain As the surface reaches a certain

temperature, the surface particles temperature, the surface particles change to gaschange to gas

– Happens before the liquid reaches its Happens before the liquid reaches its boiling pointboiling point

BoilingBoiling

Occurs throughout the liquidOccurs throughout the liquid Endothermic ProcessEndothermic Process

– Adds energyAdds energy– Temperature increasesTemperature increases– Particles move fasterParticles move faster– Temperature at which a liquid boils is its Temperature at which a liquid boils is its

boiling pointboiling point

Gas to Liquid?Gas to Liquid?

CondensationCondensation

Exothermic ProcessExothermic Process– Remove energyRemove energy– Temperature decreasesTemperature decreases– Particle movement decreasesParticle movement decreases– Particles clump togetherParticles clump together– Temperature at which a gas becomes a Temperature at which a gas becomes a

liquid is the condensation pointliquid is the condensation point Condensation and vaporization are Condensation and vaporization are

the reverse of each otherthe reverse of each other

Solid to Gas?Solid to Gas?

SublimationSublimation

Endothermic ProcessEndothermic Process– Adds energyAdds energy– Temperature increasesTemperature increases– Particle movement increasesParticle movement increases

Comparing Changes of State