Phases Of Matter

CH23

Physics (B) Fall, 2010-2011

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Phase (State) Changes

• First, what are the phases of matter?– Solid– Liquid– Gas– Plasma

• Phase depends on T and P, & amount of heat added or removed from substance

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Phases of Matter• Solids-molecules are slow moving, close together (except

ice!), have a definite shape, have a definite volume• Liquids-molecules are moving faster than solids, spreading

apart, have a definite volume, but not a definite shape….liquids take the shape of the container

• Gases-molecules in constant motion, random & free, molecules are very far apart, no definite shape, no definite volume

• Plasma-similar to a gas, but contains charged particles with ooh-koo energy, exists at very high temps (K is used)

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Phases of Matter• If Plasma exists at high temps, then how

does a Plasma TV work?

• http://videos.howstuffworks.com/science-channel/37745-deconstructed-plasma-tvs-video.htm

• How cool is that!?!

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Phase Changes-How Does a Substance Change From One to Another?

• Two things required to change phases:1. Energy Absorbed or Energy Released From Substance, i.e. Q

or Q

2. Constant Temperature: ΔT = 0, Tfinal=Tinitial

T=ONE TEMP. THE WHOLE TIME

• Phase changes can go Solid→ Liquid→ Gas

OR Gas→ Liquid → Solid

AND Solid → Gas (Sublimation)

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Phase Diagram-Solid-to-Gas

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Tem

p. (

°C)

-50

80 100 540 Heat Energy ADDED (cal)

Melting

Evaporating/Vaporizing

Phase Diagram-Gas-to-Solid

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Tem

p. (

°C)

-50

80 100 540 Heat Energy REMOVED (cal)

Freezing

Condensing

Phase Changes of Water• There are five processes that deal with

phase changes:– Evaporation– Condensation– Boiling – Freezing– Sublimation

• Let’s take a look….

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Phase Changes of Water

• Evaporation: Change of phase from liquid to gas that takes place at the surface of a liquid

• Condensation: Change of phase from gas to a liquid that takes place at the surface

• These two are direct opposite processes

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Phase Changes of Water

• Boiling: Change of Phase from Liquid to gas BENEATH a liquid’s surface

• Freezing: Change of Phase from Liquid to solid at the surface of a liquid

• These two are direct opposite processes

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Phase Change of Water• But there is one funky process:

Sublimation: The phase change from solid directly to gas from the surface of the solid

Examples: Dry Ice (CO2 solid form), Fog from snow

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Let’s Go Witness This Stuff?!

You Gotta See It To Believe It!

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