Bell Ringer 9-15-09 Solid --> Liquid = _________ Liquid --> Gas = _________ Gas --> Liquid = _________ Liquid --> Solid = _________ Solid --> Gas = __________

Gas Behavior Chapter 3 Section 3

Measuring Gases Recall: Volume- amount of space that matter fills Measured in cubic centimeters (cm3), liters (L), milliliters (mL), and other units

Measuring Gases Recall: The particles within any substance are constantly moving. Temperature- measure of the average energy of the particles in a substance Faster the particles move --> greater the energy and greater the temperature Thermometer - “speedometer” for molecules At room temp (20oC), the particles in a gas move at about 500 meters per second- twice the speed of a jet plane

Measuring Gases Pressure of the gas- force of its outward push divided by the area of the walls of the container Pressure is measured in units of pascals (Pa). Pressure = force area Ex: Higher gas pressure in a basketball keeps it inflated

1. Pressure and Volume 1. Boyle’s Law- Boyle found that when the pressure of a gas at constant temperature is increased, the volume of the gas decreases. When the pressure is decreased, the volume increases. p. 86 Boyle's Law

Examples of Boyle’s Law The bubbles exhaled by a scuba diver grow as the approach the surface of the ocean. (The pressure exerted by the weight of the water decreases with depth, so the volume of the bubbles increases as they rise.) Deep sea fish die when brought to the surface. (The pressure decreases as the fish are brought to the surface, so the volume of gases in their bodies increases, and pops bladders, cells, and membranes). Pushing in the plunger of a plugged-up syringe decreases the volume of air trapped under the plunger.

2. Pressure and Temperature Sand storm Illustration 2. Gas particles travel quickly and randomly At constant volume (closed container) Increasing temperature, increases pressure Decreasing temperature, decreases pressure

3. Charles’ Law Charles found that when the temperature of a gas is increased at constant pressure, its volume increases. When the temperature of a gas is decreased at constant pressure, its volume decreases. Balloon illustration in video Hot Air Balloons

Examples of Charles’ Law A football inflated inside and then taken outdoors on a winter day shrinks slightly. A slightly underinflated rubber life raft left in bright sunlight swells up (Why shouldn't you overinflate your life raft when your ship goes down in tropical waters?) The plunger on a turkey syringe thermometer pops out when the turkey is done (The volume of air trapped under the plunger increases when the temperature inside the turkey climbs).