1. Kinetic Theory of Gases • consists of small particles that • move rapidly in straight lines. • essentially no attractive (or repulsive) forces. • are very far apart. • very small volumes compared • volume of container occupied • kinetic energies • increase with increased temperature.

2. Properties that describe a gas • four properties: pressure (P), volume(V), temperature(T), and amount(n).

3. What is gas pressure? • force acting on a specific area. Pressure (P) = Force Area • units of atm, mm Hg, torr 1 atm = 760 mm Hg 1 atm = 760 torr

4. What is atmospheric pressure? • pressure exerted by a column of air • from top of atmosphere • to surface of earth • 1 atmosphere at sea level • depends on altitude and weather • lower at high altitudes • density of air less. • higher on a rainy day • than sunny day

5. What is a barometer? • measures pressure exerted by • gases in atmosphere. • indicates by • height in mm of mercury column.

6. Boyle’s Law (pressure-volume) law • pressure of a gas • inversely related to its volume • when T and n are constant • volume decreases • pressure increases • product P x V constant • as long as T and n unchanged P1V1 = P2V2 (T, n constant) • can be solved for any factor

7. Breathing, an example • During inhalation • lungs expand • pressure in lungs decreases • air flows towards lower pressure in lungs • During exhalation • lung volume decreases • pressure within lungs increases • air flows from higher pressure in lungs to outside

8. Calculation with Boyle’s Law Freon-12, CCl2F2, is used in refrigeration systems. What is the new volume (L) of a 8.0 L sample of Freon gas initially at 550 mm Hg after its pressure is changed to 2200 mm Hg at constant T? 1. Set up a data table: Conditions 1 Conditions 2 P1 = 550 mm Hg P2 = 2200 mm Hg V1 = 8.0 L V2 = ?

9. Calculation with Boyle’s law (continued) 2. When pressure increases, volume decreases. Solve Boyle’s Law for V2: P1V1 = P2V2 V2 = V1 x P1 P2 V2 = 8.0 L x 550 mm Hg = 2.0 L 2200 mm Hg

10. Learning Check For a cylinder containing helium gas indicate if cylinder A or cylinder B represents the new volume for the following changes (n and T are constant). 1) pressure decreases 2) pressure increases

11. Learning Check A sample of oxygen gas has a volume of 12.0 L at 600. mm Hg. What is the new pressure when the volume changes to 36.0 L? (T and n constant). A) 200. mm Hg B) 400. mm Hg C) 1200 mm Hg

12. Solution A) 200. mm Hg Data table Conditions 1 Conditions 2 P1 = 600. mm Hg P2 = ??? V1 = 12.0 L V2 = 36.0 L P2 = P1 x V1 V2 = 600. mm Hg x 12.0 L 36.0 L = 200. mm Hg

13. Charles’ law temperature -volume • Charles’ Law, • Kelvin temperature of a gas • directly related to volume • P and n are constant • temperature of a gas increases • volume increases • V1 T1= V2 T2 • (P and n constant) • rearranging Charles’ Law

14. Calculations using charles’ law A balloon has a volume of 785 mL at 21°C. If the temperature drops to 0°C, what is the new volume of the balloon (P constant)? 1. Set up data table: Conditions 1 Conditions 2 V1 = 785 mL V2 = ? T1 = 21°C = 294 K T2 = 0°C = 273 K Kelvin (K) temperature in gas calculations.

15. Calculations Using Charles’ Law (continued) 2. Solve Charles’ law for V2: V1 = V2 T1 T2 V2 = V1 x T2 T1 V2 = 785 mL x 273 K = 729 mL 294 K

16. Learning Check A sample of oxygen gas has a volume of 420 mL at a temperature of 18°C. At what temperature (in °C) will the volume of the oxygen be 640 mL (P and n constant)? 1) 443°C 2) 170°C 3) - 82°C

17. What is STP? volumes of gases can be compared at STP, Standard Temperature and Pressure, • the same temperature. • Standard temperature (T) • 0°C or 273 K • the same pressure. • Standard pressure (P) • 1 atm (760 mm Hg)

18. What is Molar volume? • standard temperature and pressure (STP), 1 mole of a gas occupies a volume of 22.4 L, its molar volume • used to form conversion factors 22.4 L and 1 mole 1 mole 22.4 L

19. Partial Pressure (Dalton’s Law) • pressure of each gas in mixture. • pressure gas would exert if • itself in container • pressure depends on total number of gas particles • not on types of particles • total pressure exerted by gases mixture • sum of partial pressures of gases • Calculate the sum of the partial pressures. Ptotal = PO2 + PHe Ptotal = 342 mm Hg + 855 mm Hg = 1197 mm Hg

20. Scuba Diving-! • When a scuba diver dives, • increased pressure causes N2(g) to dissolve in blood. • If diver rises too fast, • dissolved N2 will form bubbles in blood • "the bends" • Helium, does not dissolve in blood, • mixed with O2 to prepare breathing mixtures for deep descents.

21. Gases We Breathe • contains N2 and O2 & small amounts of other gases • O2 enters blood, while CO2 from • blood released • tissues, O2 enters cells, • release CO2 into blood. • O2 flows into tissues • partial pressure of O2 higher in blood, • lower in tissues • CO2 flows out of the tissues • partial pressure of CO2 is higher in tissues, • lower in the blood