Phase ChangesPhase Changes

Review: 4 Phases of MatterReview: 4 Phases of Matter

• SolidSolid

• LiquidLiquid

• GasGas

• PlasmaPlasma

What is a What is a Phase Change?

• It is a change from one state of It is a change from one state of matter matter (solid, liquid, gas) to another.(solid, liquid, gas) to another.

• Phase changes are Phase changes are physical physical changeschanges because: because:

- It only affects physical - It only affects physical appearance, appearance,

not chemical make-up.not chemical make-up.

- Reversible- Reversible

What happens during a What happens during a phase change?phase change?

• During a phase During a phase

change, change, heat heat

energyenergy is either is either

absorbedabsorbed or or

released.released.

What is Exothermic change?What is Exothermic change?

• Heat energyHeat energy is released as is released as

molecules slow down and move molecules slow down and move

closer together.closer together.

Example: Gas to LiquidExample: Gas to Liquid

What is Endothermic What is Endothermic change?change?

• Heat energyHeat energy is absorbed as is absorbed as

molecules speed up and expand.molecules speed up and expand.

Example: From solid to liquidExample: From solid to liquid

Types of Phase ChangesTypes of Phase Changes

What is Melting?What is Melting?

• Phase change from Phase change from a solid to a liquida solid to a liquid

• Molecules speed Molecules speed up, move farther up, move farther apart, apart, and absorb and absorb heat energyheat energy

What is Freezing?What is Freezing?

• Phase Change from Phase Change from a liquid to a solida liquid to a solid

• Molecules slow Molecules slow down, move closer down, move closer together and together and release heat release heat energy.energy.

Vaporization (Boiling)Vaporization (Boiling)• Phase change from Phase change from

a liquid to gas. It a liquid to gas. It occurs at the occurs at the boiling point of boiling point of matter.matter.

• Molecules speed Molecules speed up, move farther up, move farther apart, and apart, and absorb absorb heat energy.heat energy.

What is Evaporation?What is Evaporation?• Phase change from Phase change from

a liquid to a gasa liquid to a gas

• Molecules speed up, Molecules speed up,

move farther apart, move farther apart,

and and absorbabsorb heat heat

energy.energy.

What is Condensation?What is Condensation?• Phase change from a Phase change from a

gas to a liquid.gas to a liquid.

• Molecule slow down, Molecule slow down, move closer together move closer together and and release heat release heat energy.energy.

Sublimation is?Sublimation is?

• Phase change from a solid directly to a Phase change from a solid directly to a gas.gas.

• Liquid state Liquid state doesn’tdoesn’t happen..!!!happen..!!!

• Molecules speed up, move farther Molecules speed up, move farther apart, and apart, and absorb heat energyabsorb heat energy..

• Example: Example: As As dry icedry ice (frozen carbon dioxide gas) (frozen carbon dioxide gas)

gets warmer, it turns gets warmer, it turns

into carbon dioxide gasinto carbon dioxide gas

Deposition is?Deposition is?

• Phase change from a gas Phase change from a gas to a solid.to a solid.

• Again.. Liquid state Again.. Liquid state doesn’tdoesn’t happen..!!! happen..!!!

• Molecules slow down, Molecules slow down, move closer together move closer together and and release heat energy.release heat energy.

Melting & Boiling PointsMelting & Boiling Points• What is What is Melting PointMelting Point: :

The temperature at which a The temperature at which a solid changes into a liquid.solid changes into a liquid.

• What is What is Boiling Point:Boiling Point:

The temperature at which a The temperature at which a liquid changes into a gas.liquid changes into a gas.

• What is a What is a Freezing point?Freezing point?

Point at which liquid Point at which liquid becomes solid.becomes solid.

SummarySummary

SummarySummary

• When Heat energy is released it is called?When Heat energy is released it is called?

Exothermic changeExothermic change

Think of the prefix Think of the prefix ExoExo as Exit as Exit

SummarySummary

• When Heat energy is absorbed it is called?When Heat energy is absorbed it is called? Endothermic changeEndothermic change The prefix The prefix endoendo means in means in

Graphing a Phase ChangeGraphing a Phase Change

– Why is there no change in Why is there no change in temperaturetemperature

when changing solid to liquid and liquid to gas?when changing solid to liquid and liquid to gas?

– Because the heat energy is used get the Because the heat energy is used get the

molecules molecules

to move faster and faster, until ice changes to to move faster and faster, until ice changes to

liquidliquid

and eventually liquid will change to gasand eventually liquid will change to gas

Graphing a Phase ChangeGraphing a Phase Change

– Define melting pointDefine melting point * Melting Point happens when all the * Melting Point happens when all the molecules molecules

have so much energy that they now have so much energy that they now change change

into the liquid state of matter into the liquid state of matter

Graphing a Phase ChangeGraphing a Phase Change• What is the What is the melting point melting point and boiling and boiling point of water?point of water?

• Pure Water Pure Water meltsmelts

at at 0 C or 32 F0 C or 32 F• Pure Water Pure Water boilsboils

at at 100 C100 C or 212 or 212 F F

o o

o o

Graphing a Phase ChangeGraphing a Phase ChangeAt what At what temperature does temperature does water freeze and water freeze and become a solidbecome a solid??

•Pure Water freezes Pure Water freezes at at

0 C or 32 F0 C or 32 F

o o

•DirectionsDirections

Take out your science notebook Take out your science notebook or your phone notes and write or your phone notes and write down thedown the

following questions and answersfollowing questions and answers

1. Name six common phase changes.1. Name six common phase changes.

Melting, freezing, vaporization, condensation, Melting, freezing, vaporization, condensation,

sublimation, and deposition.sublimation, and deposition.

2. What happens to the temperature of a 2. What happens to the temperature of a

substance during a phase change?substance during a phase change?

The temperature of a substance does not The temperature of a substance does not

change during a phase change.change during a phase change.

3. What is the difference between evaporation 3. What is the difference between evaporation

and boiling?and boiling?

Evaporation takes place at the surface of a Evaporation takes place at the surface of a

liquid and occurs at temperatures below the liquid and occurs at temperatures below the

boiling point. Boiling point of pure water is boiling point. Boiling point of pure water is

100 degrees Celcius100 degrees Celcius

4. How does the energy of a system change 4. How does the energy of a system change

during a phase change?during a phase change?

Energy is either released or absorbed Energy is either released or absorbed

during a phase change.during a phase change.

5. What happens to the arrangement of water 5. What happens to the arrangement of water

molecules as water melts and freezes?molecules as water melts and freezes?

The arrangement of molecules becomes less The arrangement of molecules becomes less

orderly as water melts and more orderly as orderly as water melts and more orderly as

water freezes.water freezes.

6. What is the difference between Endothermic 6. What is the difference between Endothermic and Exothermic change?and Exothermic change?

During During endothermic changeendothermic change energy is energy is absorbed absorbed

from the surroundings, such as hot stovefrom the surroundings, such as hot stove During During exothermic changeexothermic change energy is released energy is released into the surroundingsinto the surroundings7. What are the freezing and boiling points of 7. What are the freezing and boiling points of

pure waterpure water Freezing point is 0 degree Celcius and 32 Freezing point is 0 degree Celcius and 32

degreesdegrees FahrenheitFahrenheit Boiling point is 100 degrees Celsius and 212 Boiling point is 100 degrees Celsius and 212

degrees Fahrenheitdegrees Fahrenheit

HomeworkHomework tonight……tonight……

• Complete:Complete:

“ “Molecules on the move Molecules on the move worksheetworksheet””

• Write the correct Phase of matter Write the correct Phase of matter and also include whether it was and also include whether it was an Exothermic or Endothermic an Exothermic or Endothermic changechange

• HW is due tomorrow..!! Oh yes..!HW is due tomorrow..!! Oh yes..!