1. Prentice-Hall Chapter 14.1 Dr. Yager
Properties of Gases
Prentice-Hall Chapter 14.1
Dr. Yager

2. Objectives
Explain why gases are easier to compress than solids or liquids
Describe the three factors that affect gas pressure

3. Compressibility
Compressibility is a measure of how much the volume of matter can decrease under pressure.

4. Examples of Compressibility
Car air bags
A person during a collision compresses the gas inside the bag to absorb energy.
Pneumatic tires
The tires compress as they move over bumps to smooth out the ride.
Scuba diving
Air is compressed into a tank to compensate for the water pressure.

5. Car Air Bag

6.     1892 Victor Bicycle Catalog
Victor Pneumatic Tire "Owing to the speed which has been developed on racing tracks with specially light bicycles, and specially light pneumatic tires, there has sprung up a demand for an inflated tire for road bicycles."
"It is today a question whether pneumatic tires will finally come to be acknowledged as a permanent improvement in bicycle construction or not."
"We believe we present in our Victor Pneumatic tire as good a device as can be made. We think it better than any device offered."

8. Compression
Gases are easily compressed because of the large space between gas particles.
The volume of gas particles is small compared to the total gas volume.
At room temperature the distance between each particle is about 10 times the particle diameter.

10. How is Gas Behavior Modeled?
PV = nRT
P = pressure
V = volume
n = number of moles
R = gas constant
T = temperature in Kelvins
also know as the Ideal Gas Law

11. The amount of gas (moles), volume and temperature affect pressure.

12. Amount of Gas
When you add more particles, by kinetic theory, more particles hit the sides of the container, thereby increasing pressure.

13. Volume
When you decrease the volume, by kinetic theory, the sides are closer together so more particles hit the sides more often, thus increasing the pressure.

15. Temperature
When the temperature increases, by kinetic theory, the kinetic energy of the particles increase so the speed at which the particles hit the wall increases, increasing the pressure.

17. 1. A gas is easy to compress because:
the electrons around the atoms are bouncy.
the particles repel each other like two magnets.
the space between the particles is large.
it is directly proportional to the volume.

18. 1. A gas is easy to compress because:
the electrons around the atoms are bouncy.
the particles repel each other like two magnets.
the space between the particles is large.
it is directly proportional to the volume.

19. 2. At 200 feet in ocean depth the temperature decreases and the pressure increases, so the pressure in a scuba tank
a. increases at 200 ft because the pressure increases.
b. decreases at 200 ft because the pressure increases.
c. increases at 200 ft because the temperature decreases.
d. decreases at 200 ft because the temperature decreases.

20. 2. At 200 feet in ocean depth the temperature decreases and the pressure increases, so the pressure in a scuba tank
a. increases at 200 ft because the pressure increases.
b. decreases at 200 ft because the pressure increases.
c. increases at 200 ft because the temperature decreases.
d. decreases at 200 ft because the temperature decreases.

21. 3. To maintain a constant pressure while the volume is increasing, one could:
subtract gas from the volume.
increase the temperature of the gas.
decrease the temperature of the gas.
reduce the number of moles of gas from the volume.

22. 3. To maintain a constant pressure while the volume is increasing, one could:
subtract gas from the volume.
increase the temperature of the gas.
decrease the temperature of the gas.
reduce the number of moles of gas from the volume.