1. GASES
Holt Modern Chemistry

2. KINETIC MOLECULAR THEORY
Based on the idea that particles of matter are always in motion
Explains the properties of solids, liquids and gases in terms of energy of particles and the forces between them
IDEAL GAS
An imaginary gas that fits all the assumptions of Kinetic Molecular Theory

3. KMT ASSUMPTIONS
Gases consist of large numbers of tiny particles that are far apart
Elastic collisions between gas particles and between particles and container walls
Gas particles are in continuous, rapid, random motion; possess kinetic energy (KE)
No forces of attraction or repulsion between gas particles
Average KE depend on temperature of the gas
At same T, all gases have same KE
At same T, lighter particles have higher average speed than heavier particles

4. NATURE OF GASES EXPANSION FLUIDITY LOW DENSITY COMPRESSIBILITY
Gases have no definite shape or volume and completely fill any container in which they are enclosed
FLUIDITY
Gas particles glide easily past one another or flow because attractive forces are insignificant
LOW DENSITY
About 1/1000 the density of liquid or solid because particles are so much farther apart
COMPRESSIBILITY
Gas particles which are initially very far apart are crowded closer together during compression

5. NATURE OF GASES DIFFUSION & EFFUSION DIFFUSION EFFUSION
Spontaneous mixing of the particles of two substances caused by their random motion
EFFUSION
Process by which gas particles pass through a tiny opening

6. REAL GAS
Gas that does not behave completely according to the assumptions of KMT
JOHANNES VAN DER WAALS
Real gases occupy space and exert attractive forces on each other
Highly polar gases (Ex. NH3 (g) and H2O (g) deviate from ideal behavior to a larger degree than nonpolar gases
Due to Intermolecular Force of attraction

7. PRESSURE Force per unit area on a surface
Gas pressure results from the collisions of billion of gas particles on an object
SI Unit for FORCE – Newtons (N)
BAROMETER – device used to measure atmospheric pressure

8. UNITS OF PRESSURE SI Unit ~ Pascal (Pa) (1 Pa = 1 N/m2)
1000 Pa = 1 kPa (kiloPascal)
millimeter of mercury (mmHg) ~ pressure that supports 1 mmHg column in barometer
torr 1 torr = 1 mmHg
Atmosphere (atm) ~ average atmospheric pressure at sea level and 0ºC

9. UNITS OF PRESSURE / STP Conversions
1 atm = 760 mmHg 1 mmHg = 1 torr
1 atm = 760 torr 1 atm = kPa
1 atm = Pa
STP – Standard Temperature & Pressure
Standard Temp. – 0ºC or K
Standard Pressure – 1 atm