Agenda Behavior of Gases Gas Laws Gas Laws Worksheet

Closed System A closed system does not exchange matter with its surroundings but energy can come and go as it pleases.

Kinetic Molecular Theory Empirical (based on experiments) description of gases that the gas laws are based on.

Collisions of Gas Particles

Kinetic Molecular Theory

Postulate (Assumption) 1 Gases consist of tiny particles (atoms or molecules)

Kinetic Molecular Theory Postulate (Assumption) 2 These particles are so small, compared with the distances between them, that the volume (size) of the individual particles can be assumed to be negligible (zero).

Kinetic Molecular Theory Postulate (Assumption) 3 The particles are in constant random motion, colliding with the walls of the container. These collisions with the walls cause the pressure exerted by the gas.

Kinetic Molecular Theory Postulate (Assumption) 4 The particles are assumed not to attract or to repel each other.

Kinetic Molecular Theory Postulate (Assumption) 5 The average kinetic energy of the gas particles is directly proportional to the temperature of the gas

Ideal Gases Particles in an ideal gas… have no volume. have elastic collisions. (When they collide no energy is lost) are in constant, random, straight-line motion. don’t attract or repel each other. have an avg. KE directly related to Kelvin temperature. Courtesy Christy Johannesson

Real Gases Particles in a REAL gas… have their own volume attract each other Gas behavior is most ideal… at low pressures at high temperatures in nonpolar atoms/molecules

Kinetic Molecular Theory Gases expand to fill any container. random motion, no attraction Gases are fluids (like liquids). no attraction Gases have very low densities. no volume = lots of empty space Courtesy Christy Johannesson

Gas Variables ž Four variables to describe a gas: Pressure (P) Volume (V) Temperature (T) Amount (n)

Ideal Gas Relationships As Pressure Increases, Temperature Increases By extension – As Pressure Decreases Temperature Decreases As Volume Increases, Temperature AND Pressure Decrease By extension – As Volume Decreases, Temperature and Pressure Increase As Amount (number of moles) Increases, Pressure and Temperature Increase By extension – As Amount Decreases, Pressure and Temperature Decrease In a Closed System…

Gas Law Apparatus Air Valve Temperature Sensor Pressure Gauge Air Volume