1. THE GAS LAWS Section 4.1 pg. 150 – 160 Homework: Boyle’s Law: pg. 152 # 6-9 Charles’ Law: pg. 156 # 14-17 Combined Gas Law: pg. 159 # 20-23

2. Gas Laws They are based on the temperature, pressure and volume relationships that all gases have in common 1. Boyle’s Law P 1 V 1 = P 2 V 2 2. Charles’ Law V 1 = V 2 T 1 = T 2 3. Combined Gas Law P 1 V 1 =P 2 V 2 T 1 = T 2

3. Boyle’s Law Anglo- Irish chemist Robert Boyle (1627-1691) was a founding member of the Royal Society of London.

4. Boyle’s Law Considers the effects of pressure on the volume of a gas only while temperature is held constant This is an inverse relationship: P = V P = V Boyle’s Law states: “as the pressure on a gas increases, the volume of the gas decreases proportionally if temperature and mass are constant” Boyle’s Equation: P 1 V 1 = P 2 V 2

5. Boyle’s Law “As the pressure on a gas increases, the volume of the gas decreases proportionally if temperature and mass are constant”

6. Boyle’s Law - Graphically Pressure (kPa) Volume (L) PV (kPa  L) 1003.00300 2001.52304 3001.01303 4000.74296 5000.60300

7. Demos Cartesian Diver DemoDiver ◦ “The Cartesian diver is named after the French philosopher, Rene Descartes (1596-1650), and is a very old experiment. The volume of a gas decreases as the pressure on the gas increases. As you squeeze the bottle, the pressure is transferred from your hand to the water and from the water to the air trapped inside the diver. As the volume of air in the diver gets smaller, more water enters the diver, making it heavier and less buoyant, and the diver sinks to the bottom. As the pressure is released, the air inside the diver expands and increases the buoyancy so that the diver rises.” Expanding Marshmallow DemoMarshmallow Demo ◦ “The marshmallow expands as the volume in the syringe increases and the pressure decreases. It shrinks as the volume is reduced and the pressure is increased”

8. Boyle’s Law - PRACTICE 1. A sample of gas at 1.0 atm is in a 1.0 L container. What is the pressure when the volume is changed to 2.0L? (Assume T and m are constant) P 1 V 1 = P 2 V 2 (1.0 atm) (1.0 L) = (x) (2.0 L) 1.0 atmL = 2.0 L (x) 2.0L 2.0L 0.50 atm = P 2 According to Boyle’s Law, the gas would now have a pressure of 0.50 atm

9. Boyle’s Law - PRACTICE 2. A 2.0 L party balloon at 98 kPa is taken to the top of a mountain where the pressure is 75 kPa. Assume that the temperature and mass of the gas remain the same. What is the new volume of the balloon. P 1 V 1 = P 2 V 2 (98 kPa) (2.0 L) = (75 kPa) (x) 196 kPaL = 75 kPa (x) 75 kPa 75 kPa 2.6 L = V 2 According to Boyle’s Law, the balloon would have a new volume of 2.6L

10. Practice Pg. 152 #6-9

11. Charles’ Law Jacque Charles (1746- 1823) He made the first flight of a hydrogen balloon on August 27, 1783. This balloon was destroyed by terrified peasants when it landed outside of Paris.

12. Charles’ Law Shows the relationship between temperature (must be in Kelvin) and volume of gas if pressure and mass are constant This is a direct relationship: T = VT = V Charles’ Law states: “as the temperature of a gas increases, the volume increases proportionally, provided that the pressure and mass remain constant” Charles’ Equation : V 1 = V 2 T 1 = T 2

13. Charles’ Law “As the temperature of a gas increases, the volume increases proportionally, provided that the pressure and mass remain constant”

14. Charles’ Law - Graphically When the graphs of several careful volume-temperature experiments are extrapolated, all the lines meet at absolute zero, 0K or -273° C

15. Demos Pop Can demo ◦ Charles’ Law at work

16. Charles’ Law - PRACTICE 1. A gas inside a cylinder with a movable piston is heated to 315°C. The initial volume of gas in the cylinder is 0.30 L at 25°C. What will be the final volume when the temperature is 315°C? T 1 = (25 + 273) = 298K T 2 = (315 + 273) = 588K * Remember temperature has to be in Kelvin V 2 = V 1 T 2 T 1 = (0.30 L)(588K) 298K = 0.59 L V 1 = V 2 T 1 = T 2 According to Charles’ Law, the final volume will be 0.59 L

17. Practice pg. 156 #14 - 17

18. The Combined Gas Law Combined Gas Law You can get Boyle’s Law back by assuming temperature is constant. You can get Charles’ Law back by assuming pressure is constant

19. The Combined Gas Law When Boyle’s and Charles’ laws are combined, the resulting combined gas law produces a relationship among the volume, temperature, and pressure of any fixed mass of gas. The combined gas law is a useful starting point for all cases with gases, even if one of the variables is a constant. ◦ A variable that is constant can easily be eliminated from the combined gas law equation, reducing it back to Boyle’s or Charles’ Law

20. Combined Gas Law - Practice 1. A gas cylinder with a fixed volume contains a gas at a pressure of 652 kPa and a temperature of 25°C. If the cylinder is heated to 150°C, use the combined gas law to calculate the new pressure. Because volume is constant we can cancel V 1 and V 2 because V 1 = V 2 T1 = (25 + 273) = 298 K T2 = (150 + 273) = 423 K P 1 V 1 = P 2 V 2 T 1 = T 2 P 2 = P 1 T 2 T 1 P 2 = (652kPa) (423K) 298 K P 2 = 925 kPa The gas will have a new pressure of 925 kPa

21. Combined Gas Law - Practice 2. A balloon containing helium gas at 20 °C and a pressure of 100 kPa has a volume of 7.50 L. Calculate the volume of the balloon after it rises 10 km into the upper atmosphere, where the temperature is –36 °C and the outside air pressure is 28 kPa. (Assume that no gas escapes and that the balloon is free to expand so that the gas pressure within it remains equal to the air pressure outside.) T1 = (20 + 273) = 293 K T2 = (-36 + 273) = 237 K P 1 V 1 = P 2 V 2 T 1 = T 2 V 2 = P 1 V 1 T 2 T 1 P 2 V 2 = (100kPa)(7.50 L)(237 K) (293 K)(28 kPa) V 2 = 21.6 L = 22 L According to the Combined Gas law, the volume of the balloon in the upper atmosphere will be 22L

22. SUMMARY STP: 0 °C and 101.325 kPa (exact values) SATP: 25 °C and 100 kPa (exact values) 101.325 kPa = 1 atm = 760 mm Hg (exact values) absolute zero = 0 K or –273.15 °C K = (°C) + 273 (for calculation) Boyle’s Law P 1 V 1 = P 2 V 2 Charles’ Law V 1 = V 2 T 1 = T 2 Combined Gas Law P 1 V 1 = P 2 V 2 T 1 = T 2

23. Practice Pg. 159 # 20 - 23

24. Homework Boyle’s Law: pg. 152 # 6-9 Charles’ Law: pg. 156 # 14-17 Combined Gas Law: pg. 159 # 20 – 23 Gas Laws Worksheets Pg 161 Q 1-7 QUIZ WEDNESDAY