1. The Behavior of Gases
Chapter 3 Section 3

2. Objective
You will know what types of measurements are useful when working with gases.
You will know how volume, temperature, and pressure of a gas are related.

3. Food for Thought What are the properties of gases? What is volume?
How does gas exert pressure?

4. Measuring Gases
When working with a gas, it is helpful to know its volume, temperature, and pressure.
Volume, the amount of space that matter fills, is measures in units of cubic centimeters or millimeters.
Because gas particles move and fill the space available, the volume of gas is the same as the volume of its container.

5. A helium tank the height of this girl can fill over 500 balloons
A helium tank the height of this girl can fill over 500 balloons! How is the helium on the tank different from the helium in the balloons?

6. Temperature is a measure of the average energy of random motion of the particles of a substance.
The faster the particles are moving, the greater their energy and higher the temperature.
*Particles in a gas move very fast even at ordinary temperatures!

7. Because gas particles are moving, they are constantly colliding with one another. They also collide with the walls of their container. As a result, the gasses push on the walls of the container.
The pressure of the gas is the force of its outward push divided by the area of the walls of the container.
Pressure is measured in units of pascals (Pa), or kilopascals (kPa).

8. The firmness of a gas filled object comes from the pressure of the gas.
Example: a basketball that is firm has a high pressure, a basketball that is soft has a low pressure.

9. Apply What unites are used to measure pressure?
Describe the motion of the gas particles in a container with high pressure.

10. Temperature and Volume
By looking at the picture, what appears to be the relationship between temperature and volume?

11. Charles Law
Jacques Charles examined the relationship between temperature and volume and came to this conclusion….
When the temperature of a gas increases at a constant pressure, its volume increases.
When the temperature decreases at a constant pressure, its volume decreases.

12. So…. Volume and temperature and directly proportional.
As one increases so does the other. As one decreases so does the other.

13. Pressure and Volume
Pressure is related to the volume of a container. The relationship between the two is called Boyle’s Law.
Boyle’s Law says: 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.

15. When the product of two variables is a constant, the variables are inversely proportional.

16. Pressure and Temperature
Pressure is also related to the temperature of a gas.
The higher the temperature, the faster the gas particles move.
The faster the gas particles move, the more frequently they collide with the walls of their container, and the greater the pressure will be.
When the temperature of a gas at constant volume is increased, the pressure of the gas increases.
When the temperature is decreased, the pressure of the gas decreases.

17. Practice…

18. Exit Slip
1. Describe how the motions of gas particles are related to the pressure exerted by the gas.
2. Why does pumping air into a basketball increase the pressure inside the ball?
3. Explain why increasing the temperature of a gas in a closed, rigid container causes the pressure in the container to increase.