More About Gases Charles Law GayLussacs Law Kinetic

More About Gases Charles’ Law Gay-Lussac’s Law Kinetic Molecular Theory (KMT)

Charles’ Law Jacques Charles determined the relationship between temperature and volume of a gas. He measured the volume of air at different temperatures, and observed a behavior pattern which led to his law. During his experiments pressure of the system and amount of gas were held constant.

Temperature The temperature of a gas is generally measured with a thermometer in Celsius. All calculations involving gases should be made after converting the Celsius to Kelvin temperature. Kelvin = C° + 273

Volume of balloon at room temperature Volume of balloon at 5°C

Charles’ Law Example: A gas has a volume of 3. 0 L at 127°C. What is its volume at 227 °C? V 1 V 2 = T 1 T 2 T 1 = 127°C + 273 = 400 K V 1 = 3. 0 L T 2 = 227°C + 273 = 500 K V 2 = ?

2) Plug in the variables: 3. 0 L V 2 = 400 K 500 K 3) Cross multiply and solve (500 K)(3. 0 L) = V 2 (400 K) V 2 = 3. 75 L

Gay-Lussac’s Law: P and T In Gay-Lussac’s Law the pressure exerted by a gas is directly related to the Kelvin temperature. Volume and the amount of gas are constant. P 1 = P 2 T 1 T 2

Calculation with Gay-Lussac’s Law A gas has a pressure at 2. 0 atm at 18°C. What is the new pressure when the temperature is 62°C? (Volume and the amount of gas are constant) 1. Set up the problem: P 1 = 2. 0 atm P 2 = T 1 = 18°C + 273 = 291 K T 2 = 62°C + 273 = 335 K ?

Calculation with Gay-Lussac’s Law (continued) 2. Solve Gay-Lussac’s Law for P 2: P 1 = P 2 T 1 T 2 P 2 = P 1 x T 2 T 1 P 2 = 2. 0 atm x 335 K = 2. 30 atm 291 K

What is Kinetic Molecular Theory (KMT)? • A theory that envisions molecules in motion • Best describes properties and behaviors of gases * Imagines particles of a gas like ping pong balls, moving and crashing into each other and the walls of a container in a three-dimensional space.

Basic Principles of KMT 1. Gases consist of tiny particles.

2. Gas particles are very far apart; the volume occupied by a gas consists mostly of empty space (typically about 99. 9% empty).

3. Gas particles move randomly in all directions, traveling in straight lines.

Gas particles collide with each other and with the walls of the container without losing energy.

4. The higher the average speed of the particles, the higher the temperature of that substance.