Download Chapter 14.1 PPT

Properties of Gases
Prentice-Hall Chapter 14.1
Dr. Yager
Objectives

Explain why gases are easier to compress
than solids or liquids

Describe the three factors that affect gas
pressure
Compressibility
Compressibility is a measure of how much the
volume of matter can decrease under pressure.
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.
Car Air Bag
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."
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.
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
The amount of gas (moles), volume and
temperature affect pressure.
nRT
P
; n  P
V
nRT
P
; T  P
V
nRT
P
;  V  P
V
Amount of Gas
When you add more particles, by kinetic theory,
more particles hit the sides of the container,
thereby increasing pressure.
nRT
P
; n  P
V
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.
nRT
P
;  V  P
V
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.
nRT
P
; T  P
V
1. A gas is easy to compress because:
a. the electrons around the atoms are bouncy.
b. the particles repel each other like two
magnets.
c. the space between the particles is large.
d. it is directly proportional to the volume.
1. A gas is easy to compress because:
a. the electrons around the atoms are bouncy.
b. the particles repel each other like two
magnets.
c. the space between the particles is large.
d. it is directly proportional to the volume.
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.
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.
3. To maintain a constant pressure while
the volume is increasing, one could:
subtract gas from the volume.
b. increase the temperature of the gas.
c. decrease the temperature of the gas.
d. reduce the number of moles of gas from the
volume.
a.
3. To maintain a constant pressure while
the volume is increasing, one could:
subtract gas from the volume.
b. increase the temperature of the gas.
c. decrease the temperature of the gas.
d. reduce the number of moles of gas from the
volume.
a.