Behavior of Gases

Kinetic Theory• Gases are composed of SMALL,

SEPARATE particles called MOLECULES.

• Gas molecules are in CONSTANT MOTION

• All COLLISIONS between particles are PERFECTLY ELEASTIC

• The MOLECULES of a gas display no ATTRACTION or REPULSION for one another.

Kinetic Theory

• The AVERAGE KINETIC ENERGY of the molecules is DIRECTLY PROPORTIONAL to the KELVIN temperature of the gas.

Ideal GasGas whose BEHAVIOR conforms to

the KINETIC THEORY -it is THEORETICAL.

Real GasParticles in a real gas…

Have their own volumeAttract each other

Gas behavior is most ideal…At low pressuresAt high temperaturesIn nonpolar atoms/molecules

Characteristics of Gases Gases expand to fill any container

Random motion, no attraction

Gases are fluids (like liquids)

No attraction

Gases have very low densities

No volume = lots of empty space

Gases can be compressed

No volume = lots of space

Gases undergo diffusion & effusion

Random motion

Gas Pressure:

Pressure = FORCE ÷ AREA = ____ atm

Atmospheric Pressure - the PRESSURE the earth’s ATMOSPHERE exerts due to its WEIGHT.

Barometer: Instrument used to measure �ATMOSPHERIC PRESSURE Invented by � TORRICALLI

Key Units101.325 kPa (kilopascal)

1 atm

760 mm Hg

760 torr

14.7 psi

101.3 kPa = 1 atm = 760 torr = 760 mm Hg

Standard Temperature & PressureStandard Temperature & Pressure

0°C 273 K

1 atm 101.325 kPa-OR-

STP

• Always use absolute temperature (Kelvin) when working with gases.

ºF

ºC

K

-459 32 212

-273 0 100

0 273 373

32FC 95 K = ºC + 273

Temperature