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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)
3
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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