Gas Laws

1. Gas Laws

2. Standards SPS5. Students will compare and contrast the phases of matter as they relate to atomic and molecular motion. a. Compare and contrast the atomic/molecular motion of solids, liquids, gases and plasmas. b. Relate temperature, pressure, and volume of gases to the behavior of gases.

3. Essential Questions • Why does it take longer to cook grits in Denver than in Savannah? • What floats your boat? How are mass and volume related to density? • How do the arrangement and energy of particles determine the phases of matter? • How do changes in pressure, volume, or temperature of a gas relate to each other?

4. Words To Know • Pressure • Atmosphere (atm) • Compressible • Boyle’s Law • Temperature • Charles’s Law • Gay-Lussac’s Law

5. Animation: Pressure and Temperature • Pressure and Volume

6. Description • Gas particles are in constant motion. • The particles of gases are not held by the forces that solids and liquids are. • Gases are compressible (they can be squeezed into small spaces or expanded to fill very large spaces. • Gases have 3 unique properties: Temperature, Pressure and Volume. • The properties can be predicted by three gas laws: • Boyle’s Law • Charles’s Law • Gay-Lussac’s Law

7. Pressure • When the particles are colliding against the walls of the container, they exert a force on the sides. The collective force of all the particles exerts a pressure on the walls. • Pressure is the amount of force exerted over a certain area. • The more particles that hit the sides, the higher the pressure. • Pressure is described in units called atmospheres (atm). • One atm, is equal to the pressure of air at sea level.

8. Compressibility • Since the particles of gases are not in contact with each other, there is a lot of space between them. This makes them compressible. • Compressible means that they are easily pushed into smaller spaces.

9. Boyle’s Law • When gases are compressed, their particles are closer together and they collide with the container walls more often. • When the volume of the container decreases, the pressure increases. • When the volume of the container increases, the pressure decreases. • Boyles law states: • For a fixed amount of gas at a constant temperature, the volume of the gas increases as the pressure decreases.

10. Boyle’s Law in Real Life • When the cap on the soda is closed, it is under pressure. The gas particles are not allowed to escape. • When the soda is not under pressure, the particles are allowed to spread out and escape causing the soda to go flat.

11. Charles’s Law • The faster the particles move, the higher the temperature of the substance. • The slower the particles move, the lower the temperature of the substance. • When the temperature of a gas increases, its particles speed up and collide with the sides of the container. • As the temperature increases, the volume of the gas increases. • As the temperature decreases, the volume of the gas decreases.

12. Charles’s Law • States that for a fixed amount of gas at constant pressure, the volume of the gas increases as the temperature increases.

13. Charles’s Law Real-Life Example • Tires inflated on a warm day look flat on a cold day. (The temperature decreases, so the volume decreases).

14. Charles’s Law Real-Life Example • Balloons blown up during a hot day will decrease in size overnight as the temperature cools. (The temperature decreases, so the volume decreases).

15. Gay-Lussac’s Law • When the temperature of a gas increases, its particles hit the sides of the container more often. • Gay-Lussac’s Law refers to containers that have rigid sides (sides cannot move). • As the temperature increases, the collision of the particles increase causing the pressure to increase.

16. Gay-Lussac’s Law • States that as the volume remains constant, the pressure of the gas increases as the temperature increases.