1. Warmup: 3 minutes 1. List 3 reasons why this astronaut is wearing a space suit. What happens if his space suit is torn? 2. What is ‘volume’? The amount of space occupied by a sample of matter

2. Phase Diagrams and Some Gas Laws Find your phase diagram of H 2 O and your calculator

3. Evaporation Cooling process Molecules at the surface break away and become gas. Only those with enough KE escape

4. Kinetic Energy % ofMolecules% ofMolecules High temp. Low temp. Few molecules have very high kinetic energy Energy needed to overcome intermolecular forces average kinetic energy of sample = temperature

5. First sealed: molecules escape liquid surface As molecules build up above the liquid some condense back to a liquid. SD OC LA Dynamic equilibrium As time goes by, vaporization rate remains constant but the condensation rate increases because there are more molecules to condense. When Vaporization Rate = Condensation Rate, equilibrium has been reached The total amount of liquid and vapor remains constant

6. Boiling A liquid boils when the vapor pressure = the external pressure normal boiling point: is the temperature a substance boils at 1 atm pressure How can we Change the Boiling Point? Lower external pressure (going up into the mountains, place liquid in a vacuum).

7. Melting point Boiling point Phase diagram: expresses the phase of a substance as a function of T and P Melting point: P&T where solid becomes liquid Boiling point: P&T where liquid becomes vapor

8. Melting point Boiling point Triple point: P&T where all 3 phases of matter are present Critical point: maximum P & T where vapor can be liquefied; higher values make phase indistinguishable equilibrium lines: 2 phases coexist; slight P or T change triggers phase change (ex. snowboarding)

9. Identify the phase of H 2 O that exists at these coordinates: A: T = -5°C, P = 1 atm B: T = 105°C, P= 5 atm C: T = 5°C, P = 2 atm D: T= 30°C P= 0.000001 atm melting Melting point Boiling point A B D C

10. Volume (cm 3 ) Pressure (kPa) 5450 10330 15250 20200 25160 30130 35100 4075 1. Plot the data above, collected by Robert Boyle. 2. What is the relationship between volume and pressure ? 3. What would be the volume of a gas at 225 kPa? Volume (cm 3 ) Pressure (kPa) Boyle’s Law

11. P 1 V 1 = P 2 V 2 old pressure old volume new pressure new volume Pressure and volume are inversely proportional: vacuum demo

12. 1. A sample of oxygen gas occupies a volume of 250 mL at 740. torr pressure. What volume will it occupy at 800. torr pressure? Assume constant temperature. V1V1 P1P1 P2P2 V2V2 InitialAfter P 1 =P 2 = V 1 =V 2 = T 1 =T 2 = 740 torr 800 torr ? 250 mL ----- P 1 V 1 = P 2 V 2 V 2 = V 2 = 230 mL

13. 2. A sample of carbon dioxide occupies a volume of 3.50 liters at 125 kPa pressure. What pressure (in mmHg) would the gas exert if the volume was decreased to 2.00 liters? V1V1 P1P1 P2P2 V2V2 InitialAfter P 1 =P 2 = V 1 =V 2 = T 1 =T 2 = 125 kPa 2.00 L ? 3.50 L ----- P 1 V 1 = P 2 V 2 P 2 = P 2 = 219 kPa P 2 = 1640 mmHg

14. 3. Ammonia gas occupies a volume of 450 mL as a pressure of 720 mm Hg. What volume (in liters) will it occupy at standard pressure? V1V1 P1P1 P2P2 V2V2 InitialAfter P 1 =P 2 = V 1 =V 2 = T 1 =T 2 = 720 mmHg 760 mmHg ? 450 mL ----- P 1 V 1 = P 2 V 2 V 2 = V 2 = 426 mL wait…need liters! 0.43 L

15. Charles’ Law a) Graph the data. b) How are temperature and volume related? c) At what temperature would volume be zero? volume (cm 3) Temperature ( ⁰ C) T and V have a direct, linear relationship V 1 = V 2 T 1 T 2 Temp. ( ⁰ C) Volume (cm 3 ) 3080 -1070 -5060 -9050 -13040 -17030 -21020 -25010 -273 ⁰ C

16. V 1 = V 2 T 1 T 2 (V 1 ) = 2.5cm 3 291.5K 311.5K Answer: 2.3 cm 3 1. Some students think that teachers are full of hot air. If Ms Jonson takes a deep breath of air at 18.5°C and it heats to 38.5°C and the volume expands to 2.5 cm 3, what was the starting volume of air? Assume constant pressure. P 1 = cons.P 2 = cons. V 1 = ?V 2 = 2.5 cm 3 T 1 = 18.5°C T 2 = 38.5°C 291.5 K 311.5 K

17. 2. Oxygen gas is at a temperature of 40.0°C when it occupies a volume of 2.30 L. To what temperature (in °C) should it be raised to occupy a volume of 6.50 L? V1V1 T1T1 T2T2 V2V2 InitialAfter P 1 =P 2 = V 1 =V 2 = T 1 =T 2 = 40.0°C 313 K 6.50 L ? 2.30 L ----- T 2 = 885 K wait…need Celsius -273 T 2 = 612°C

18. Gay-Lussac’s Law Temperature Pressure How are pressure and temperature related? P and T have a direct, linear relationship

19. 1. Before a trip from New York to Boston, the pressure of an automobile tire is 1.8 atm at 20.°C. At the end of the trip, the pressure gauge reads 1.6 atm. What is the new Celsius temperature of the air inside the tire? (Assume the tires had a constant volume throughout the whole trip). InitialAfter P 1 =P 2 = V 1 =V 2 = T 1 =T 2 = P1P1 T1T1 P2P2 T2T2 1.8 atm1.6 atm -------- 20°C = 293 K ? T 2 = 260 K or -13°C 1.8 atm = 1.6 atm 293 K T 2

20. 2. Determine the pressure (in atm) when a constant volume of gas at standard pressure is heated from 20.0°C to 30.0°C. P1P1 T1T1 T2T2 P2P2 InitialAfter P 1 =P 2 = V 1 =V 2 = T 1 =T 2 = 20°C 293 K 1.00 atm ? 30°C 303 K ----- P 2 = 1.03 atm