Properties of Gases

1) they exert pressure

2) they exist at different, measurable temperatures

3) they take up space (have volume)

4) they have low (weak) intermolecular forces between molecules(that's why they are gases)

Kinetic Theory

1) the particles in a gas are assumed to be small, hard spheres with an insignificant volume

2)  the motion of particles in a gas is rapid and random.

3)  the collisions between gas particles are perfectly elastic

Gas Pressure

results from the force exerted by a gas per unit surface area of an object

Atmospheric Pressure

a result of the collisions of atoms and molecules in the air with objects

Absolute Zero

the theoretical temperature at which gas molecules have no kinetic energy and where they  have zero volume and exert zero pressure

Intermolecular Forces

the interactions between disruptive motions of particles in a liquid and the attractions among the particles

Vaporization

the conversion of a liquid to a gas or a vapor

Evaporation

the conversion of a liquid to a gas or vapor at a temperature below the boiling point.  Occurs at the surface of a liquid.

Vacuum

an empty space with no particles or matter

Barometer

a device used to measure atmospheric pressure

Vapor Pressure

a measure of the force exerted by a gas above a liquid

Dynamic Equilibrium

when the rate of evaporation of a liquid equals the rate of condensation of a vapor

Manometer

a device used to measure vapor pressure

Boiling Point

the temperature at which the vapor pressure of the liquid is just equal to the external pressure on the the liquid

Normal Boiling Point

the temperature at which a liquid boils at a apressure of 101.3 kPa (or 760 mm Hg or 1 atm)

Condensation

transition from the vapor (gas) phase to the liquid phase

Melting

transition from the solid phase to the liquid phase

Freezing

the transition from the liquid phase to solid phase

Sublimation

transition from the solid phase to the gas phase

Critical Point

the temperature above which a substance cannot exist as a liquid.  It will be a gas no matter what pressure

Triple Point

the only set of conditions at which all three phases can exist in equilibrium with one another