THE GAS LAWS Section 4.1 pg. 150 – 160

Gas Laws They are based on the temperature, pressure and volume relationships that all gases have in common 1. Boyle’s Law 2. Charles’ Law 3. Combined Gas Law

Boyle’s Law Anglo- Irish chemist Robert Boyle ( ) was a founding member of the Royal Society of London.

Boyle’s Law Considers the effects of pressure on the volume of a gas only while ___________________________ This is an inverse relationship: P = V P = V Boyle’s Law states: “as the pressure on a gas increases, the _____________of the gas decreases proportionally if temperature and mass are constant” Boyle’s Equation:

Boyle’s Law “As the pressure on a gas increases, the volume of the gas decreases proportionally if temperature and mass are constant”

Boyle’s Law - Graphically Pressure (kPa) Volume (L) PV (kPa  L)

Demos Cartesian Diver DemoDiver ◦ “The Cartesian diver is named after the French philosopher, Rene Descartes ( ), and is a very old experiment. The volume of a gas decreases as the pressure on the gas increases. As you squeeze the bottle, the pressure is transferred from your hand to the water and from the water to the air trapped inside the diver. As the volume of air in the diver gets smaller, more water enters the diver, making it heavier and less buoyant, and the diver sinks to the bottom. As the pressure is released, the air inside the diver expands and increases the buoyancy so that the diver rises.” Expanding Marshmallow DemoMarshmallow Demo ◦ “The marshmallow expands as the volume in the syringe increases and the pressure decreases. It shrinks as the volume is reduced and the pressure is increased”

Boyle’s Law - EXAMPLE 1. A sample of gas at 1.0 atm is in a 1.0 L container. What is the pressure when the volume is changed to 2.0L? (Assume T and m are constant)

Boyle’s Law – EXAMPLE 2. A 2.0 L party balloon at 98 kPa is taken to the top of a mountain where the pressure is 75 kPa. Assume that the temperature and mass of the gas remain the same. What is the new volume of the balloon.

Practice – Boyle’s Law WB PG 35 ALL

Charles’ Law Jacque Charles ( ) He made the first flight of a hydrogen balloon on August 27, This balloon was destroyed by terrified peasants when it landed outside of Paris.

Charles’ Law Shows the relationship between ______________ (must be in Kelvin) and volume of gas if pressure and mass are constant This is a direct relationship: T = VT = V Charles’ Law states: “as the ___________ of a gas increases, the volume increases proportionally, provided that the pressure and mass remain constant” Charles’ Equation :

Charles’ Law “As the temperature of a gas increases, the volume increases proportionally, provided that the pressure and mass remain constant”

Charles’ Law - Graphically When the graphs of several careful volume-temperature experiments are extrapolated, all the lines meet at absolute zero, 0K or -273° C

Demos Pop Can demo ◦ Charles’ Law at work

Charles’ Law - EXAMPLE 1. A gas inside a cylinder with a movable piston is heated to 315°C. The initial volume of gas in the cylinder is 0.30 L at 25°C. What will be the final volume when the temperature is 315°C?

Charles’ Law – EXAMPLE 1. A Hot Air Balloon is being prepared for flight when the air temperature is 20˚C. The propane burner warms the air in the balloon causing the volume to expand by 20%(Each 1.00L becomes 1.20L). What is the final temperature of the air in the balloon.

Charles’ Law Practice WB PG 36 ALL

The Combined Gas Law Combined Gas Law You can get Boyle’s Law back by assuming temperature is constant. You can get Charles’ Law back by assuming pressure is constant

The Combined Gas Law When Boyle’s and Charles’ laws are combined, the resulting ______________________ produces a relationship among the volume, temperature, and pressure of any fixed mass of gas. The combined gas law is a useful starting point for all cases with gases, even if one of the variables is a constant. ◦ A variable that is constant can easily be eliminated from the combined gas law equation, reducing it back to Boyle’s or Charles’ Law

Combined Gas Law - EXAMPLE 1. A gas cylinder with a fixed volume contains a gas at a pressure of 652 kPa and a temperature of 25°C. If the cylinder is heated to 150°C, use the combined gas law to calculate the new pressure.

Combined Gas Law - EXAMPLE 2. A balloon containing helium gas at 20 °C and a pressure of 100 kPa has a volume of 7.50 L. Calculate the volume of the balloon after it rises 10 km into the upper atmosphere, where the temperature is –36 °C and the outside air pressure is 28 kPa. (Assume that no gas escapes and that the balloon is free to expand so that the gas pressure within it remains equal to the air pressure outside.)

SUMMARY STP: 0 °C and kPa (exact values) SATP: 25 °C and 100 kPa (exact values) kPa = 1 atm = 760 mm Hg (exact values) absolute zero = 0 K or – °C K = (°C) (for calculation) Boyle’s Law P 1 V 1 = P 2 V 2 Charles’ Law V 1 = V 2 T 1 = T 2 Combined Gas Law P 1 V 1 = P 2 V 2 T 1 = T 2

Practice WB PG 37 ALL

Homework Boyle’s Law: pg. 152 # 6-9 Charles’ Law: pg. 156 # Combined Gas Law: pg. 159 # 20 – 23 Gas Laws Worksheets Section 4.1 Review pg 161 ◦ Qs # 1-7