1. States of Matter
Chapter 18 in

2. Particle Theory of Matter
Theory states that all matter is made up of tiny particles in constant motion.
Thermal Expansion= matter expands as it gets warmer and contracts when it cools.
Water is exception!!! Water expands as it freezes.

3. Particles of Matter
Atoms – smallest unit of an element that maintains the properties of that element
Molecules – 2 or more atoms combined in a fixed ratio
Solids – particles vibrate in fixed locations
Liquids – particles slide past one another but are still attracted to one another
Gases – particles move very fast; random and rapid

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Solids
Main characteristics:
Definite shape
Definite volume
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5. Solids Two types of solids: Crystalline= made up of crystals
Amorphous= do not keep their shape

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Liquids
Two characteristics:
No definite shape
Always take shape of their container
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7. Liquids Viscosity= liquid’s resistance to flow…
Ex: honey has high viscosity because its slow to move

8. Liquids
Surface tension – a force that acts on particles at the surface of a liquid; causes some liquids to form droplets

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Gases
Several characteristics:
No definite shape
No definite volume…expand forever!
Fill available space in container
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10. Gases
Particles can be compressed or pushed together… Ex: bike tire, hair spray can

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Plasma
Gas-like mixture of charged particles
Plasma has high temperatures (energy)
Ex: aurora borealis, lightning
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12. Change of State
Change of state – change of a substance from one physical form to another
To change the state, energy must be added or removed

13. Melting Point Melting= change of solid to liquid.
Melting pt. – temp at which a substance changes from a solid to a liquid.
Energy must be added…endothermic (the substance gains energy)

14. Freezing Pt. Freezing=change of liquid to solid.
Freezing pt. – temp at which a liquid changes into a solid
Energy is removed…exothermic
Freezing point of a substance is equal to its melting point.

15. Vaporization Liquid to Gas Evaporation Boiling Particles throughout
Vaporization at the
surface of the
liquid. The temp
may be below the
boiling point.
Particles throughout
the liquid change
to a gas. Occurs
the pressure inside
the bubbles (vapor pressure)
equals the outside pressure
(atmospheric pressure).

16. Effects of Pressure on Boiling Point
Atmospheric pressure – weight of gases that make up the atmosphere
Water boils at 100°C only at sea level
As altitude increases, pressure decreases, boiling pt. lowers
As altitude decreases, pressure increases, boiling pt. increases

17. Condensation and Sublimation
Condensation= change of substance from a gas to a liquid.
Condensation is the same as the boiling pt. at a given pressure
Energy is removed…exothermic
Sublimation= change of substance from a solid to a gas.
Energy is gained…endothermic

18. Change of Temperature vs. Change of State
When substances lose or gain energy, they either change their temperature OR their state. They do not do both at the SAME time.
At temperature change does NOT occur until a change of state is complete.

19. Heat of vaporization
Heat of fusion

20. Solid
Liquid
Gas