Change of phase fall 2010

Agenda Bell work

• Notes: Change of Phase

• States of Matter Phet Simulation

• Pass in Lab Reports

• Define Specific Heat Capacity

• Distinguish between High and Low Specific Heat.

• Give an example of each

• How does water’s Specific heat control earth’s climate

• What is special about Islands and Peninsula's?

Change of PhaseChange of Phase

March 14, 2013March 14, 2013

ObjectivesObjectives

1.1. Explain changes in phase according to Explain changes in phase according to heat and energyheat and energy

2.2. Define each of the phase changesDefine each of the phase changes

Heat TransferHeat Transfer

When matter changes phase, a transfer of When matter changes phase, a transfer of thermal energy is involvedthermal energy is involved

EvaporationEvaporation

Liquid changes to gasLiquid changes to gas

Molecules that gainMolecules that gain

kinetic energy at the surface kinetic energy at the surface

get bumped free get bumped free

Becomes gas phase above Becomes gas phase above the liquidthe liquid

EvaporationEvaporation

Molecules that leave the liquid have the Molecules that leave the liquid have the most energy most energy

Energy of the liquid decreasesEnergy of the liquid decreases

Temperature of the liquid goes downTemperature of the liquid goes down

EX. PerspirationEX. Perspiration

Would evaporation be a cooling process if Would evaporation be a cooling process if there were no transfer of molecular energy there were no transfer of molecular energy from water to the air above?from water to the air above?

BoilingBoiling

Evaporation occurring within a liquid as Evaporation occurring within a liquid as well as its surfacewell as its surface

Bubbles of vapor form Bubbles of vapor form in the liquid and are in the liquid and are buoyed to the surface, buoyed to the surface, where they escapewhere they escape

Boiling like evaporation is a cooling Boiling like evaporation is a cooling processprocess

Boiling water is in thermal equilibriumBoiling water is in thermal equilibrium

It is being cooled by It is being cooled by boiling as fast as it boiling as fast as it is being heated by is being heated by energy from the energy from the heat sourceheat source

Since boiling is a cooling process, would it Since boiling is a cooling process, would it be a good idea to cool your hot, sticky be a good idea to cool your hot, sticky hands by dipping them into boiling water?hands by dipping them into boiling water?

CondensationCondensation

Gas to a LiquidGas to a Liquid

High energy molecules close to the surface High energy molecules close to the surface become attracted to the liquidbecome attracted to the liquid

Hit the surface with increased kinetic energyHit the surface with increased kinetic energy

Raising the temperature of the waterRaising the temperature of the water

Gas has a lot of energy to give upGas has a lot of energy to give up

If the water level in a dish of water remains If the water level in a dish of water remains unchanged from one day to the next, can unchanged from one day to the next, can you conclude that no evaporation or you conclude that no evaporation or condensation is taking place?condensation is taking place?

Melting and FreezingMelting and Freezing

Melting - solid to a liquidMelting - solid to a liquid

heat is absorbed the molecules vibrate heat is absorbed the molecules vibrate more and more breaking the attractive more and more breaking the attractive forcesforces

Freezing - liquid to a solidFreezing - liquid to a solid

energy is taken from the liquid, molecular energy is taken from the liquid, molecular motion slows down motion slows down

attractive forces between attractive forces between them bind them togetherthem bind them together

SublimationSublimation

Molecules jump directly from solid phase Molecules jump directly from solid phase to gaseous phaseto gaseous phase

Snow and ice melting on a hot sunny daySnow and ice melting on a hot sunny day

Dry ice in airDry ice in air

DepositionDeposition Molecules jump directly from gas phase to Molecules jump directly from gas phase to

solid phasesolid phase

Snow forming Snow forming high in the high in the atmosphereatmosphere