1. Chapter 3 Section 2 Notes
The Gas Laws

2. Review Remember that pressure is force divided by area
The SI unit for pressure is the Pascal
What happens if the same force is distributed over a smaller area?

3. Pressure in Gases
Collisions between particles of a gas and the walls of a container cause the pressure in a closed container of gas.
The more frequent the collisions, the greater the pressure.

4. Factors that affect Gas Pressure
Factors that affect the pressure of an enclosed gas are
Temperature
Volume
The number of particles.

5. Temperature
Raising the temperature of a gas will increase its pressure if the volume of the gas and the number of particles are constant.
How would tire pressure vary as a car goes from rest to driving for two hours on the highway?

6. Volume
Reducing the volume of a gas increases its pressure if the temperature of the gas and the number of particles are constant.
How does increasing and decreasing your chest cavity’s volume affect air flowing into and out of your lungs?

7. Breathing

8. Interesting Fact
Do you know why well to do households from the Victorian Era had “fainting couches?”
Women wore whalebone corsets which are tightly laced and restricted women from taking deep breaths.
As a result, women had low levels of oxygen in their blood causing them to faint.

9. Victorian Corset Dress
Ouch!

10. Number of Particles
Increasing the number of particles will increase the pressure of a gas if the temperature and volume are constant.
If you fill a bike tire to the maximum volume and then increase the number of particles, what will happen to the tire?

11. Charles’ Law 1. If temperature increases, the volume increases
Volume is directly proportional to temperature (K) of a gas if pressure and number of particles are constant
In other words, as one increases the other increases.
1. If temperature increases, the volume increases
2. If temperature decreases, the volume decreases

12. Liquid Nitrogen on Balloon
Experiment taking it further

13. Charles’ Law
What happens to car tires in the summer months verses the winter months?

14. Boyle’s law 1. If volume of a gas decreases, its pressure increases.
The volume of a fixed amount of gas varies inversely with the pressure of the gas if the temperature and number of particles remain constant.
In other words, as one increases, the other decreases.
1. If volume of a gas decreases, its pressure increases.
2. If volume of a gas increases, its pressure decreases.

15. The Combined Gas Law
The relationships described by Boyle’s Law and Charles’ Law can be described by a single law called the combined gas law.
The combined gas law allows scientists to deal with situations in which multiple variables are changing.

16. How do hot air balloons work?