**characteristics of gas** -

- possible for substance to coexist as solid, liquid, and gas at the same time
**vapor**- gaseous form of a substance normally existing as liquid/solid- expands to fill the container it’s in (gas volume = volume of container)
- pressure added to gas >> gas gets compressed easily >> volume decreases
- form homogeneous mixtures (regardless of type of gases involved)

** pressure** - force acted upon a given area

- P = F/A
**newton**(N) - SI unit for force, kg-m/s2**pascal**(Pa) - SI unit for pressure, N/m2- kPA = 1000 Pa
- bar = 105 Pa, approximate atmospheric pressure at sea level

- barometer - invented by Evangelista Torricelli, measures atmospheric pressure
- manometer - used to measure pressure of liquids/gases, similar to barometer

- standard atmospheric pressure = pressure needed to support column of mercury 760 mm high
- atm = 760 mm Hg, 760 torr = 1.01325 x 105 Pa = 101.325 kPa
- 1 torr = 1 mm Hg

** Boyle’s Law** - pressure-volume relationship

- volume of gas (at constant temperature) inversely proportional to pressure
- P1V1 = P2V2

** Charle’s Law** - temperature-volume relationship

- volume of gas (at constant pressure) directly proportional to temperature
- V1/T1 = V2/T2

** Avogadro’s Law** - quantity-volume relationship

- law of combining volumes - at given pressure/temperature, volumes of reacting gases exist in simple ratios
- equal volumes of gases at same temperature/pressure have equal numbers of molecules
- volume of gas (at constant pressure/temperature) directly proportional to number of moles of gas
- V = constant x n