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States of Matter
Ch. 10
The Nature of Gases
10-1
States of Matter (Review)• Remember…
– Solids have volume and shape; vibrating but fixed position
– Liquids have volume and NO shape; slide past each other
– Gases have NO volume or shape• Particles are the
farthest away from each other
Kinetic Theory (GAS)• Kinetic Theory states that tiny
particles of matter are in constant, random motion.
– Particles are far apart, not attracted to each other
– Travel in straight paths, independent of one another at high speeds (1660km/hr)!
– Elastic collision = when gas particles collide no energy is lost
• Kinetic Energy = the energy of moving objects
Gas Pressure
• Gas Pressure = force exerted by a gas per unit of surface area of an object.
• Vacuum = empty space, no particles no pressure.
Atmospheric Pressure• Atmospheric pressure (atm) = collisions of
air molecules with objects.
• Barometer = used to measure atmospheric pressure.
• Pascal (Pa) = SI unit of pressure
• 1 atm = 101.3kPa = 760 mm Hg = 14.7 psi
• Ex: 253 mm Hg = ? atm
253 mm Hg x 1 atm = 0.333 atm
760mm Hg
Pressure vs. Elevation
1) Elevation increases,Atm Pressure decreases
Temperature• Temperature = average kinetic
energy of the particles in a material– Ex: when water is heated its particles are moving much faster than when it is cold
2) As Temperature
Kinetic Energy (faster)
As Temperature
Kinetic Energy (slower)
Temperature vs. Pressure3) Temperature increases, Pressure increases
The Nature of Liquids
10-2
Vapor
Vaporization = liquid to a gas
Vapor pressure = force due to gas above liquid in sealed container
Evaporation vs. BoilingEvaporation = occurs at surface of liquid that is NOT boiling.Boiling = vaporization throughout the liquid due to heat or pressureBoiling Point = temperature at which the vapor pressure of liquid is equal to the external (atmospheric) pressure.
Draw!
Vapor Pressure < Atm Pressure Vapor Pressure > Atm Pressure
AP
VP
AP
VP
4) AltitudeBoiling Point
ex: Boiling point in Mammoth is 95°C
5) Atm Pressure Boiling Pt
ex: Boiling point in Death Valley is 105°C
The Nature of Solids
10-3
Solids
• Melting Point = temperature at which solid turns to liquid.
• Freezing Point = liquid solid
• Freezing Point = Melting Point!
• Most have crystalline structure.
• Some are amorphous (lack structure); ex: glass, rubber, plastic
Changes of State
10-4
Changing State• Changes of State:
– Melting:
S L– Freezing:
L S– Evaporation:
L G– Condensation:
G L– Sublimation:
S G– Deposition:
G S
Freezing
Phase Diagram• Phase Diagram = gives
the temperature and pressure at which a substance exists as a solid, liquid, and gas.
– Triple Point = set of conditions in which all 3 phases (solid/liquid/gas) exist together.