states of matter ch. 10. the nature of gases 10-1

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.