I. Physical PropertiesI. Physical Properties

GasesGases

A. Kinetic Molecular A. Kinetic Molecular TheoryTheoryA. Kinetic Molecular A. Kinetic Molecular TheoryTheory

Particles in an ideal gas…• have no (very small) volume.• have elastic collisions. • are in constant, random, straight-

line motion.• don’t attract or repel each other.• have an avg. KE directly related to

Kelvin temperature.

C. Characteristics of C. Characteristics of GasesGasesC. Characteristics of C. Characteristics of GasesGasesGases expand to fill any container.

• random motion

Gases are fluids (like liquids).

Gases have very low densities.• lots of empty space

C. Characteristics of C. Characteristics of GasesGasesC. Characteristics of C. Characteristics of GasesGasesGases can be compressed.

• lots of empty space

Gases undergo diffusion & effusion.• random motion

D. TemperatureD. TemperatureD. TemperatureD. Temperature

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

E. PressureE. PressureE. PressureE. Pressure

area

forcepressure

Which shoes create the most pressure?

7

Atmospheric PressureAtmospheric PressureAtmospheric PressureAtmospheric Pressure

Atmospheric pressureis the pressure exerted by a column of air from the top of the atmosphere to the surface of the Earth.

Copyright © 2009 by Pearson Education, Inc.

E. PressureE. PressureE. PressureE. Pressure

Barometer• measures atmospheric pressure

Mercury Barometer

Aneroid Barometer

E. PressureE. PressureE. PressureE. Pressure

Manometer• measures contained gas pressure

U-tube Manometer Bourdon-tube gauge

E. PressureE. PressureE. PressureE. Pressure

KEY UNITS AT SEA LEVEL

101.325 kPa (kilopascal)

1 atm

760 mm Hg

760 torr

14.7 psi

2m

NkPa

F. STPF. STPF. STPF. STP

Standard Temperature & PressureStandard Temperature & Pressure

0°C 273 K

1 atm 101.325 kPa-OR-

STP

G. VolumeG. VolumeG. VolumeG. Volume

Volume- The space occupied by the gas. They have an indefinite volume, they will fill any container.

Units of measure: L liter or ml milliliter

At STP, one mole of gas occupies 22.4 L of volume