PHASE CHANGESPHASE CHANGES

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Phases Changes in Matter: Phases Changes in Matter: (Also examples of Physical Changes)(Also examples of Physical Changes)

1. Melting1. Melting

2. Freezing2. Freezing

3. Vaporization3. Vaporization

4. Condensation4. Condensation

5. Sublimation5. Sublimation

Physical Change: a substance changes from one form to another, but it remains the same kind of substance. No new matter is formed.

Solid-Liquid Phase ChangesSolid-Liquid Phase Changes

MeltingMelting: the change of a solid to a : the change of a solid to a

liquid.liquid.

1. Occurs when a substance absorbs 1. Occurs when a substance absorbs

heat energy.heat energy.

2. The crystal structure of the particles2. The crystal structure of the particles

breaks down, allowing the particles to breaks down, allowing the particles to

flow freely around one another.flow freely around one another.

Melting-pointMelting-point: : the temperature at which a the temperature at which a

solid changes to asolid changes to a liquid. (Ice melts at 0°C)liquid. (Ice melts at 0°C)

MeltingMelting

Liquid-Solid Phase ChangesLiquid-Solid Phase Changes

FreezingFreezing: the change of a liquid into a solid.: the change of a liquid into a solid.1. occurs when a substance loses heat energy.1. occurs when a substance loses heat energy.

Freezing-pointFreezing-point: the temperature at which a substance : the temperature at which a substance changes from a liquid to a solid.changes from a liquid to a solid.

1. The freezing point of a substance is equal to 1. The freezing point of a substance is equal to its its

melting point. ( ice melts at 0°C and water melting point. ( ice melts at 0°C and water freezes at 0°C)freezes at 0°C) AlcoholsAlcohols: have freezing points much lower than 0°C.: have freezing points much lower than 0°C.

1. Used in automobile antifreeze.1. Used in automobile antifreeze.2. Even the coldest winter temperatures will not 2. Even the coldest winter temperatures will not

cause the water in the radiator to freeze.cause the water in the radiator to freeze.

FreezingFreezing

Liquid-Gas Phase ChangesLiquid-Gas Phase Changes

VaporizationVaporization: : the change of a substance from a the change of a substance from a liquid to a gas.liquid to a gas.

1. Particles in a liquid absorb enough1. Particles in a liquid absorb enough heat energy to escape from the heat energy to escape from the liquid phase.liquid phase.

EvaporationEvaporation: if vaporization takes place at the : if vaporization takes place at the surface of the liquid.surface of the liquid. CondensationCondensation: if a substance in the gas phase : if a substance in the gas phase loses heat energy, it changes into a loses heat energy, it changes into a liquid.liquid. ExampleExample: 1) a cold glass iced drink tends to : 1) a cold glass iced drink tends to become wet on the outside. This is become wet on the outside. This is because water vapor condenses.because water vapor condenses. 2) Rain2) Rain

CondensationCondensation

Liquid-Gas Phase ChangesLiquid-Gas Phase Changes

C. C. BoilingBoiling: particles inside a liquid change to gas, and : particles inside a liquid change to gas, and then the particles travel to the surface of the then the particles travel to the surface of the liquid and into the air.liquid and into the air.

D. D. Boiling-pointBoiling-point: the temperature at which a liquid boils. : the temperature at which a liquid boils. Water boils at 100°C.Water boils at 100°C.

1. Related to the pressure of the air above it.1. Related to the pressure of the air above it.a. the lower the air pressure ( the less the a. the lower the air pressure ( the less the

“ “push” of the air pressing down), the more push” of the air pressing down), the more easily the bubbles of gas can form within easily the bubbles of gas can form within the liquid and then escape. the liquid and then escape. Lowering the air pressure lowers the boiling point.Lowering the air pressure lowers the boiling point.

b. at high altitudes the air pressure is much b. at high altitudes the air pressure is much lower, so you would be able to boil water atlower, so you would be able to boil water at ordinary room temperature.ordinary room temperature.

Solid-Gas Phase ChangesSolid-Gas Phase Changes

SublimationSublimation: when a substance’s : when a substance’s surface particles escapesurface particles escape directly into the gas directly into the gas phase. They do not phase. They do not pass through the liquid pass through the liquid phase.phase.

ExampleExample: Dry Ice: Dry Icewww.youtube.com/embed/ukhtimOxECk

SublimationSublimationDry IceDry Ice

Deposition: Gas to SolidDeposition: Gas to Solid

When water vapor When water vapor in air loses so in air loses so much energy it much energy it turns directly into a turns directly into a solid.solid.

Frost!Frost!

Energy in Phase ChangeEnergy in Phase Change

DEPOSITION

More About the Phase ChangesMore About the Phase Changes

Earth is known as the “water” planet.Earth is known as the “water” planet. 1. ¾ of the Earth’s surface is water1. ¾ of the Earth’s surface is water 2. 1% of the Earth’s atmosphere exists in 3 phases2. 1% of the Earth’s atmosphere exists in 3 phases

a. Icea. Ice b. Liquid waterb. Liquid water c. Water vaporc. Water vapor

A solid substance has less energy than the same A solid substance has less energy than the same substance in the liquid phase.substance in the liquid phase.

A gas usually has more energy than the liquid phase of A gas usually has more energy than the liquid phase of the same substance.the same substance.

Ice has less energy than liquid water.Ice has less energy than liquid water. Steam has more energy than ice or liquid water.Steam has more energy than ice or liquid water.

More About the Phase ChangesMore About the Phase Changes Because energy content is responsible for the different phases Because energy content is responsible for the different phases

of matter, substances can be made to change phase by adding of matter, substances can be made to change phase by adding or taking away energy.or taking away energy.

*The easiest way to do this is to heat or cool the *The easiest way to do this is to heat or cool the substance.substance.

ExamplesExamples: 1) Liquid water is put into freezer to remove : 1) Liquid water is put into freezer to remove heat and make ice.heat and make ice.

2) On a stove you add heat to make liquid2) On a stove you add heat to make liquid water turn to steam.water turn to steam.

Physical ChangePhysical Change: a substance changes from one form to another, but : a substance changes from one form to another, but it remains the same kind of substance. No new it remains the same kind of substance. No new matter is formed.matter is formed.

Chemical Properties/ChangesChemical Properties/Changes

Chemical PropertiesChemical Properties: : The properties that The properties that describe how a substance changes into other newdescribe how a substance changes into other newsubstances.substances.ExampleExample: The ability of a substance to burn.: The ability of a substance to burn.

1. 1. FlammabilityFlammability: The ability to burn. (Hydrogen): The ability to burn. (Hydrogen)2. 2. Supporting-BurningSupporting-Burning (Oxygen) (Oxygen)

Chemical ChangesChemical Changes: : The changes that substancesThe changes that substancesundergo when they turn into other substances.undergo when they turn into other substances.ExampleExample: The process of burning.: The process of burning.

Chemical Properties/ChangesChemical Properties/Changes

A A Chemical PropertyChemical Property describes describes a substance’sa substance’sability to change into a different substanceability to change into a different substance; ;

A A Chemical ChangeChemical Change is the process by which theis the process by which thesubstance changessubstance changes..

Chemical ReactionChemical Reaction: : ((another name for a chemical changeanother name for a chemical change) ) The process in which the physical and chemicalThe process in which the physical and chemicalproperties of the original substance change as aproperties of the original substance change as anew substance with different physical andnew substance with different physical andchemical properties is formed.chemical properties is formed.