2. A gas is composed of particles, usually molecules or atoms. Small hard spheres, negligible volume and far apart. No attractive forces. Gases fill their containers with shape and volume.

3. The particles in a gas move rapidly in constant random motion. Travel in straight lines and move independently. Change directions when there are collisions. Ave speed of oxygen is 155 km/h. Speed impeded due to collisions with air and other molecules: causes random walk.

4. All collisions are perfectly elastic.

Kinetic energy is transferred from on e particle to another during collisions. Total KE remains constant.

1. Force is exerted by particles when colliding. Force of one gas particle is extremely small.

2. Gas Pressure is the result of simultaneous collisions of billions upon billions of gas particles with an object.

3. If there are no gas particles, there are no collisions and no pressure: Vacuum - resulting empty space.

4. Atmospheric pressure results from the collisions of air molecules with objects. Gravity hold air molecules and causes pressure. Air thinner as climb in elevation.

5. Barometers measure atmospheric pressure. SI unit of pressure is the Pascal (Pa). Early units mm Hg, and Atmosphere. Sea level = 101.3 kPa (STP).

6. Standard atmosphere (1atm) is the pressure required to support 760 mm Hg in a mercury barometer at 25^oC.

7. Aneroid barometer does not contain Hg. Uses metal diaphragm.

1. When heated, some kinetic energy is absorbed, some increases kinetic energy.

2. Not all molecules in a gas are moving with the same kinetic energy.

3. There is a wide range of kinetic energy in a sample. When heated the"average kinetic energy" increases, as does the range of energy.

4. Increase of average kinetic energy causes increase in temperature.

5. Cooling causes particles to move more slowly and average kinetic energy declines.

6. Absolute zero is the temperature at which the motion of particles theoretically ceases. Defined as 0K (Kelvin) = -273^oC.Never has been actually produced in laboratory.

7. Kelvin temperature scale is directly proportional to average kinetic energy. 200 K has 2X kinetic energy as 100 K.

1. Liquid particles are also in motion. They "slide" past each other.

2. Unlike gases, they are not completely independent. Intermolecular forces.

3. Particles vibrate and spin in fixed positions.

4. Particles do not have enough KE to overcome intermolecular forces. Forces also reduce space between molecules.

5. Liquids are denser than gases.

6. Increasing pressure on liquids (and solids) has little effect (no compressibility). Liquids and solids are called condensed states of matter.

7. 2 properties that effect forces are vapor pressure and boiling point.

1. Evaporation or vaporization is the conversion of a liquid to a gas or vapor below its boiling point.

2. Molecules with a minimum KE break away from the surface. Some collide with air and return, others escape.

3. When heated there is an increase in average kinetic energy, and increase in evaporation.

4. Since only molecules with higher kinetic energy leave first, remaining molecules are lower in average KE: cooling effect. Example: perspiration-cooling effect; remaining molecules absorb more body heat.

5. Evaporation in closed container creates vapor pressure above the liquid.

6. After time Rate of evaporation =rate of condensation: dynamic equilibrium.

7. Increase in temperature, increases KE and vapor pressure - more molecules above liquid.

8. Increased collisions with walls = increase in pressure.