Download - Introduction to gases
GASESReference text: 14.1 page 413-417
THREE STATES OF MATTER Solid
Liquid
Gas
Which has a specific volume? Which has a specific shape?
GASES AND THEIR UNIQUE PROPERTIES Compressibility – how much the volume
of matter decreases under pressure
A gas can be squeezed into a small space
See the all the space between the gas particles? The particles can be squeezed closer together under pressure
FACTORS AFFECTING GAS PRESSURE Pressure is the force the gas molecules
exert on the container as they collide with it
Four variables to describe a gas:Pressure (P): measured in kilopascals (kPa)Volume (V): measured in liters (L)Temperature (T): measured in kelvins (K)Amount (n): measured in number of moles
AMOUNT OF GAS When you pump air into a container, you
increase the amount of gas inside the tire,
which increases the number of collisions between gas particles,
which increases the pressure
Relationship is direct: If you double the amount of gas, the pressure
will double
Fewer gas particles, lower pressure
More gas particles, higher pressure
In a sealed container, gases move from an area of high pressure to low pressure
VOLUME If the volume of a container is reduced,
the pressure will increase
If the volume of a container is increased, the pressure will decrease
Relationship is inverse If the volume is doubled, the pressure will
decrease by half
TEMPERATURE If the temperature is increased, the
particles will move faster,
Which causes more collisions between particles
Which increases the pressure
Increasing the temperature causes the pressure to increase
Decreasing the temperature will cause the pressure to decrease
Relationship is directAs the temperature is doubled, the pressure is doubledAs the temperature is decreased by half, the pressure will
decrease by half
QUESTIONS1. Why is a gas easy to compress?
2. List three factors that can affect gas pressure.
3. Why does a collision with an air bag cause less damage than a collision with a steering wheel? (extra help)
4. How does a decrease in temperature affect the pressure of a contained gas?
5. If the temperature is constant, what change in volume would cause the pressure of an enclosed gas to be reduced to one quarter of its original volume?
6. What happens to particle motion as the temperature increases? What if it decreases?
7. Write a paragraph explaining how the compressed gas in an aerosol can force paint out of the can. Describe how the gas pressure inside the can changes as the paint is sprayed, and identify the variable that causes this change. Refer to figure 14.5 in the text.