More About GasesCharles’ LawGay-Lussac’s LawKinetic Molecular Theory (KMT)

Charles’ LawJacques 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

room temperature

Volume of balloon at 5°C

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? V1 V2

T1 T2

=

T1 = 127°C + 273 = 400K

V1 = 3.0 L

T2 = 227°C + 273 = 500K

V2 = ?

2) Plug in the variables:

2) Plug in the variables:

(500K)(3.0L) = V2 (400K)(500K)(3.0L) = V2 (400K)

V2 = 3.75 LV2 = 3.75 L

3.0L V23.0L V2

400K 500K400K 500K

=

=3) Cross multiply and

solve3) Cross multiply and

solve

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.

P1 = P2

T1 T2

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:

P1 = 2.0 atm P2 =

T1 = 18°C + 273 T2 = 62°C + 273 = 291 K = 335 K

?

Calculation with Gay-Lussac’s Law (continued)

2. Solve Gay-Lussac’s Law for P2:

P1 = P2

T1 T2

P2 = P1 x T2

T1

P2 = 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.