Gas Laws Chapter 14

Factors Effecting Gases  1. Temperature (T)  a measure of the average kinetic energy (movement) of particles in a sample of matter  If the kinetic energy of particles increases, the temperature of the substance increases.

Temperature Units of temperature can be measured in: 1.Celsius 2.Fahrenheit 3.Kelvin Who uses these temperature scales? U.S.A. uses Fahrenheit The rest of the world uses Celsius Scientists use Kelvin

Temperature Important equations needed to do temperature conversions: °F = 1.8 (°C) + 32 K = °C + 273

Volume 2. Volume (V)  the amount of space an object takes up *Gases have an indefinite shape and size depending on pressure and temperature *Gases are compressible and expandable Units of volume can be measured in: 1.mL or L 2.cm 3

Amount 3.Amount (n)  how much of a substance is present Units of amount can be measured in: 1.***Moles (the unit of measurement we use for ALL gas laws) 2.Grams 3.Number of molecules

Pressure 4. Pressure (P)  the force per unit area P = force/area

Pressure Units of pressure can be measured in: 1.Pascals (Pa) 2.Millimeters of mercury (mm Hg) 3.Torr 4.Newton per meter squared (N/m 2 ) 5.Atmospheres (atm)

Pressure At standard temperature and pressure (STP) = O° C and 1 atm, the following pressure conversions hold true: 1 atm = 760 mm Hg = 760 torr = kPa

Boyle’s Law  If the temperature is constant, as the pressure of a gas increases, the volume decreases.  P 1 V 1 =P 2 V 2

Example A balloon contains 30.0 L of helium gas at 103 kPa. What is the volume of helium when the balloon rises to an altitude where the pressure is only 25.0 kPa?

Example The pressure on 2.50 L of N 2 O changes from 105 kPa to 40.5 kPa. If the temperature does not change, what will the new volume be?

Charles’s Law  As the temperature of a gas increases, the volume increases if the pressure is constant.

Example On hot days, you may have noticed that potato chip bags seem to “inflate”, even though they have not been opened. If you have a 250. mL bag at a temperature of 19°C, and I leave it in my car which has a temperature of 60°C, what will the new volume of the bag be?

Example A 4.00 L sample of air at 35°C expands to 5.50 L when heated. What is the new temperature of the air?

Gay-Lussac’s Law  As the temperature of an enclosed gas increases, the pressure increases if the volume is held constant.

Example The gas in a used aerosol can is at a pressure of 103 kPa at 25°C. If the can is thrown onto a fire, what will the pressure be when the temperature reaches 828°C?

Example The pressure in a car tire is 198 kPa at 27°C. After a long drive, the pressure is 225 kPa. What is the temperature of the air in the tire? Assume that the volume is constant.

Combined Gas Laws  Incorporates all 3 gas laws already learned  Only the amount of gas is held constant.

Example  A 350 mL sample of helium gas is collected at 22.0°C and 99.3 kPa. What volume would this gas occupy at STP?