1. Agenda 3/31/2015 Slip Quiz Part 1 Ch13 SGCM 13.4 Phase changes and labette(s) Homework Slip quiz Part 2

2. Slip Quiz Part 1 1. The Combined Gas Law is shown by A.KE = ½ mv 2 B PV = constant C PV = nRTD P 1 V 1 = P 2 V 2 T 1 T 2 2. The Ideal gas law is shown by which equation above? What assumptions are made for an Ideal gas?

3. 5 Aday- Part 1 1. The Combined Gas Law is shown by … P 1 V 1 = P 2 V 2 T 1 T 2

4. 5 Aday- Part 1 2. The Ideal gas law is given by PV=nRT An ideal gas is assumed to consist of particles that have negligible volume compared to the distances between particles, the particles are in constant (random) motion with average kinetic energy given by ½mv 2 where m is mass and v is velocity, there are no significant forces of attraction between particles and perfectly elastic collisions.

5. Study Guide for Content Mastery Section 13.4 Phase Changes Phase change PhaseEnergy InitialFinalRequiredreleased CondensationGasLiquid ✔ DepositionGasSolid ✔ FreezingLiquidSolid ✔ MeltingSolid liquid ✔ SublimationSolidgas ✔ Vaporizationliquidgas ✔

6. Transitions Between Phases – that require energy from the surroundings Solid liquid gas vaporization melting Energy content (or enthalpy H) sublimation Why do those cans you use to clean your keyboard feel so cold when you use them?

7. Transitions Between Phases that release energy into the surroundings Solid liquid gas condensation freezing Energy content (or enthalpy H) -ΔH Exothermic Physical processes deposition

8. Study Guide for Content Mastery Section 13.4 Phase changes 7. Temperature at which a liquid is converted into a crystalline solid – freezing point. 8. Temperature at which the forces holding a crystalline lattice together are broken. – melting point. 9. Temperature at which the vapor pressure of a liquid equals the external or atmospheric pressure – boiling point.

9. Phase Diagram for H 2 O Region II Region III Region I 3 ·2 A 4

10. Study Guide for Content Mastery Section 13.4 Phase changes 10. What variables are plotted on a phase diagram? Temperature and Pressure. 11. a) Region I vapor b) Region II solid c) Region III liquid 12. Point 2 is the normal freezing point of water. 13. The temperature at point 3 is 100.00°C

11. Study Guide for Content Mastery Section 13.4 Phase changes 14. Line A represents the temperatures and pressures at which solid water and water vapor coexist. 15. What is point 4 called? What does it represent? Point 4 is called the critical point and it represents the pressure and temperature above which water cannot exist as a liquid.

12. Assessment – Group (one report) Section 13.4 Phase changes 1.Why are fountains often found in enclosed courtyards of houses in hot and dry countries. (Hint: evaporation requires energy.) 2.Rank the boiling points of water for each of the following locations increasing order. Daytona Beach, Florida (altitude:sea level); Death Valley, California (altitude 86m below sea level); Mount Shasta, California (altitude: 669 m). Explain your reasoning.

13. 1. Why are fountains often found in enclosed courtyards of houses in hot and dry countries? Fountains are often found in enclosed courtyards of houses in hot and dry countries because as the water from the fountain falls through the air it absorbs energy from the hot air which cools the air. The liquid water uses the energy it absorbs from the air to change phase and become water vapor molecules via evaporation. (This process also makes the air less dry.)

14. 2.Mount Shasta (669m) lowest b.pt (less than 1 atm, less than 100°C) Daytona Beach (sea level, 1 atm) normal boiling point for water, 100°C. Death Valley (86 m below sea level, greater than 1atom) boiling point higher than 100°C. “The temperature at which the vapor pressure of a liquid equals the external or atmospheric pressure is called the boiling point.” (p. 406) At high altitude (like Mount Shasta) water will boil at a temperature below 100°C because

15. …its molecules will escape from the liquid phase in sufficient numbers to exert a vapor pressure equal to the external pressure at a lower temperature since the atmospheric pressure at high altitude will be less than 1 atm. At Daytona Beach (sea level) the atmospheric pressure will be 1 atm and so the water will boil at its normal value, 100°C. However, in Death Valley (86 m below sea level) the external pressure will be great than 1 atm and so the boiling point of the water will be higher than 100°C as more…

16. …energy will be required to cause enough molecules to escape from the liquid phase in sufficient numbers to exert a vapor pressure equal to the external pressure.

17. Homework Review, study, practice – Ch 13 and 14 test preparation. Use notes, use your assessment packet and study guide, use multiple choice questions, use online test questions, flash cards. Check and correction Gas Law Calculations Continued worksheet using power point slide worked answers. Complete Test preparation questions, as much as you can. We will go over in class TOMORROW.

18. Slip-Quiz Part 2 1.Which of the following is an example of an endothermic physical process? A combustion of gasoline B freezing water C photosynthesis of glucose D evaporation 2. Write an expression for the kinetic energy of a particle of mass m with velocity v.