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# Introduction to gases

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### Introduction to gases

1. 1. Reference text: 14.1 page 413-417
2. 2.  Solid  Liquid  Gas  Which has a specific volume?  Which has a specific shape?
3. 3.  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
4. 4.  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
5. 5.  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
6. 6. Fewer gas particles, lower pressure More gas particles, higher pressure
7. 7.  In a sealed container, gases move from an area of high pressure to low pressure
8. 8.  If the volume of a container is reduced, the pressure will increase
9. 9.  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
10. 10.  If the temperature is increased, the particles will move faster,  Which causes more collisions between particles  Which increases the pressure
11. 11.  Increasing the temperature causes the pressure to increase
12. 12.  Decreasing the temperature will cause the pressure to decrease  Relationship is direct  As the temperature is doubled, the pressure is doubled  As the temperature is decreased by half, the pressure will decrease by half
13. 13. 1. 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.