KINETIC THEORY The word kinetic indicates motion. The Kinetic Theory describes the motion of gas particles.

KINETIC THEORY The Kinetic Theory has a few assumptions: One assumption is that the gas particles are very tiny and spread out. Therefore, a gas is mostly EMPTY SPACE.

KINETIC THEORY Another assumption: Gas particles are always in motion. They bump into each other and into the walls of the container. They undergo ELASTIC collisions!

KINETIC THEORY Elastic Collisions are collisions that do NOT lose or transfer energy when they collide. Gas particles have little or no attraction for each other. They don’t repel each other either.

KINETIC THEORY Not all gas particles have the same amount of kinetic energy. Some are fast and some are slow. The kinetic energy is proportional to the temperature of the gas particles. When the temperature is high, the particles have more energy and move faster.

BOYLE’S LAW In a sealed container, the volume and the pressure of a gas are inversely proportional at constant temperature.

BOYLE’S LAW Inversely proportional means that as the volume goes up, the pressure goes down. OR if the volume goes down, the pressure goes up. Mathematically it looks like this: V1P1 = V2P2

BOYLE’S LAW Consider some gas particles trapped inside a jar. If the volume of the jar is 500ml at a pressure of 740mm Hg, what will the volume be if the pressure changes to 1500mm Hg? V1P1 = V2P2

(500ml)*(740mm Hg) = (V2)*(1500mm Hg) BOYLE’S LAW (500ml)*(740mm Hg) = (V2)*(1500mm Hg) V2 = 246.7ml

BOYLE’S LAW Try a second problem: A balloon has a volume of 0.8 liters at a pressure of 1.2 atm. What would be the new pressure if the volume is increased to 2.3 liters? Remember: V1P1 = V2P2

Answer: 0.417 atm Now let’s look at some data of pressure and volume of a gas in a sealed container. What happens to the volume of a gas when the pressure decreases? Pressure Volume 133 kPa 0.63 liters 122 kPa 0.69 liters 111 kPa 0.75 liters 100 kPa 0.84 liters 88 kPa 0.95 liters 77 kPa 1.09 liters 66 kPa 1.27 liters

That’s right, the volume increases! Take a look at the graph of the data, it forms a beautiful hyperbola.

Let’s Review Boyle’s Law Use the equation V1P1 = V2P2 to solve problems when the pressure and volume change while the temperature is constant. A pressure vs. volume graph is in the shape of a hyperbola. Don’t mix units, be consistent!

Standard Pressure Standard pressure is a perfect day on the beach, right at sea level. The values are: 101.3 kPa = 1.0 atm = 760 mmHg Get your calculator, it’s time to go to Moodle and do some Boyle’s Law Problems.