Chapter 23 Change of Phase

1. Chapter 23Change of Phase

2. Phases of Matter: • Plasma • Gas • Liquid • Solid Energy

3. The Atmosphere

5. Pressure and Temperature According to Gay-Lussac’s Law, as the pressure of a gas decreases, there is a corresponding decrease in the temperature. This is why the temperature of the air drops with increasing altitude.

6. Evaporation • Evaporation is a change of phase from liquid to gas that takes place at the surface of a liquid. • Temperature is related to kinetic energy and molecules in a liquid are constantly bumping into each other; some gain energy while others lose energy. • Occasionally, some molecules gain enough energy to escape the surface of the liquid. • They are now considered a vapor, molecules in the gaseous phase

7. Evaporation is a cooling process. • When water molecules escape the surface of liquid water, they leave behind molecules with less kinetic energy. This results in a net cooling of the liquid.

9. The Water Cycle

10. Condensation • The opposite process to evaporation is condensation • Condensation is the changing of a gas to a liquid • Condensation is a warming process • Condensation of water vapor forms clouds

11. Types of Clouds

12. Pyrocumulus Cloud formed by forest fire:

13. Relative Humidity • Relative Humidity is the amount of moisture in the air compared to what the air can "hold“ • Warm air can hold more water vapor than cool air Temperature

14. Thunderstorms

15. Thunderstorms • Thunderstorms can spawn severe weather • High Winds • Lightning • Hail • Tornados

16. Tornado Preparedness • Move to an interior portion of your home or school, away from windows during a tornado • Do not open windows to equalize pressure! This is a myth! • Have evacuation routes planned out ahead of time • Do not stay in your car. Your car can become a flying projectile with you in it!

17. Boiling • Evaporation takes place at the surface of a liquid • A change in phase from liquid to gas can also take place beneath the surface of a liquid • The gas that forms beneath the surface causes bubbles to form • These bubbles are buoyed upward to the surface where they escape, this change in phase is called boiling

18. Freezing • When energy is withdrawn from a liquid, molecular motion slows down until the forces of attraction between the molecules causes them to get closer to one another • The molecules then vibrate about a fixed position which causes a solid to form. This change in phase from liquid to solid is called freezing • If sugar or salt is dissolved in the water, the freezing temperature will be lowered. • These “foreign” molecules or ions get in the way of water molecules that ordinarily would join them together in the ice crystal structure