Phase Changes
Where is this used?
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Conditioning of buildings, such as 'ice-storage'
Cooling of heat and electrical engines
Cooling: food, beverages, coffee, wine, milk products, green houses
Medical applications: transportation of blood, operating tables, hot-cold therapies
Waste heat recovery
Solar power plants
Spacecraft thermal systems
Thermal comfort in vehicles
Thermal protection of electronic devices
Thermal protection of food: transport, hotel trade, ice-cream, etc.
Textiles used in clothing
Computer cooling
Review: 3 Phases of Matter
• Solid
• Liquid
• Gas
What happens during a phase change?
• During a phase change,
heat energy is either
absorbed or released.
• Heat energy is released as
molecules slow down and
move closer together.
• Heat energy is absorbed
as molecules speed up
and expand.
Types of Phase Changes
• Types of Phase Changes
Melting
• Phase change from a
solid to a liquid
• Molecules speed up,
move farther apart, and
absorb heat energy
Freezing
• Phase Change from a
liquid to a solid
• Molecule slow down,
move closer together
and release heat
energy.
Vaporization (Boiling)
• Phase change from a
liquid to gas. It occurs at
the boiling point of
matter.
• Molecules speed up,
move farther apart, and
absorb heat energy.
Evaporation
• Phase change from a
liquid to a gas on the
surface of a liquid
(occurs at all
temperatures).
• Molecules speed up,
move farther apart, and
absorb heat energy.
Condensation
• Phase change from a
gas to a liquid.
• Molecule slow down,
move closer together
and release heat
energy.
Sublimation
• Phase change from a
solid to a gas.
• Molecules speed up,
move farther apart, and
absorb heat energy.
Deposition
• Phase change from a
gas to a solid.
• Molecules slow down,
move closer together
and release heat
energy.
Graphing a Phase Change
What is wrong with this picture?
Melting & Boiling Points
• Melting Point: The temperature at which a
solid changes into a liquid.
• Boiling Point: The temperature at which a
liquid changes into a gas.
• What is a Freezing point? Compare the
freezing and melting points of water.
Summary
Graphing a Phase Change
– Why is there no change
in temperature during a
phase change?
– Define melting and
boiling points.
– What is the melting
point and boiling point
of water?
– At what temperature
does water freeze and
become a solid?