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.