STAR ReviewStandard 4 Gases and Their Properties

Gas PressureGas molecules inside a volume are

constantly moving around freely. During this molecular motion they

frequently collide with each other and with the surface of any enclosure there may be in.

Movement of Gases

STP Standard Temperature and Pressure

Equivalent STP valuesStandard Temperature Standard Pressure

0oC 1 atm273.15 K (SI units) 101,325 Pa (SI units)

32oF 101.325 kPa (SI units)  760 mm Hg   14.7 lb/in2

  1 bar

Absolute Zero Absolute zero is the point where no

more heat can be removed from a system,

0 K or -273.15°C In classical kinetic theory, there should

be no movement of individual molecules

• One of the first instruments used to measure gas pressure was designed by the Italian scientist Evangelista Torricelli (1608-1647).

• He invented the barometer, an instrument that measures the pressure exerted by the atmosphere.

Boyle’s Law P1V1=P2V2 As pressure increases, volume decreases

Charles’s Law

Gay-Lussac’s Law

Combined Gas Law

Ideal Gas LawPV = nRTP= pressure (atm)V= volume (Liters)N= # of molesR= constant (0.821 L.atm/mol.K)T= temperature (Kelvin)