1. Physical Properties Gases

2. Kinetic Molecular Theory b Particles in an ideal gas… have no volume. The particles in a gas are very far apart. have elastic collisions. are in constant, random, straight- line motion. don’t attract or repel each other. have an avg. KE directly related to Kelvin temperature.

3. Real Gases Real Gases b Particles in a REAL gas… have their own volume attract each other b Gas behavior is most ideal… at low pressures at high temperatures

4. Characteristics of Gases b Gases expand to fill any container. b Gases have very low densities. no volume = lots of empty space b Gases can be compressed Compressibility—a measure of how much the volume of matter decreases under pressure

5. Characteristics of Gases b Gases undergo diffusion & effusion. Diffusion –the tendency of molecules to go from areas of high concentration to area of low concentration Effusion – the process when a gas escapes through a tiny hole in a container

6. Temperature Temperature ºF ºC K -45932212 -2730100 0273373 K = ºC + 273 b Always use the Kelvin scale when working with gases.

7. Pressure Pressure Which shoes create the most pressure?

8. Pressure Pressure Barometer measures atmospheric pressure Mercury Barometer Aneroid Barometer

9. Pressure Pressure b KEY UNITS AT SEA LEVEL 101.325 kPa (kilopascal) 1 atm 760 mm Hg 760 torr 14.7 psi

10. STPSTP Standard Temperature & Pressure 0°C 273 K 1 atm101.325 kPa -OR- STP

11. Temperature Conversions b Convert each of the following to Kelvin temperatures 27 °C -50 °C -273 °C

12. b Answers 300 K 223 K 0 K

13. Temperature Conversions b Convert each of the following to degrees Celsius 273 K 350. K 100. K 20. K

14. b Answers 0 °C 77 °C -173 °C -253 °C

15. Pressure Conversions 1. Convert 109 kPa to atm 2. Convert 0.62 atm to mm Hg 3. Convert 0.3587 atm to kPa 4. Convert 29.32 mmHg to kPa

16. b Answers 1.1.08 atm 2.470 mm Hg 3.36.345 kPa 4.3.91 kPa

17. The Gas Laws Gases

18. Boyle’s Law b The pressure and volume of a gas are inversely related at constant mass & temp P V

19. V T Charles’ Law b The volume and absolute temperature (K) of a gas are directly related at constant mass & pressure

20. P T Gay-Lussac’s Law b The pressure and absolute temperature (K) of a gas are directly related at constant mass & volume

21. Combined Gas Law Combined Gas Law P1V1T1P1V1T1 = P2V2T2P2V2T2 P 1 V 1 T 2 = P 2 V 2 T 1

22. GIVEN: V 1 = 473 cm 3 T 1 = 36°C = 309K V 2 = ? T 2 = 94°C = 367K WORK: P 1 V 1 T 2 = P 2 V 2 T 1 Gas Law Problems b A gas occupies 473 cm 3 at 36°C. Find its volume at 94°C. TT VV (473 cm 3 )(367 K)=V 2 (309 K) V 2 = 562 cm 3

23. GIVEN: V 1 = 100. mL P 1 = 150. kPa V 2 = ? P 2 = 200. kPa WORK: P 1 V 1 T 2 = P 2 V 2 T 1 Gas Law Problems b A gas occupies 100. mL at 150. kPa. Find its volume at 200. kPa. PP VV (150.kPa)(100.mL)=(200.kPa)V 2 V 2 = 75.0 mL

24. GIVEN: V 1 = 7.84 cm 3 P 1 = 71.8 kPa T 1 = 25°C = 298 K V2 = ?V2 = ? P 2 = 101.325 kPa T 2 = 273 K WORK: P 1 V 1 T 2 = P 2 V 2 T 1 (71.8 kPa)(7.84 cm 3 )(273 K) =(101.325 kPa) V 2 (298 K) V 2 = 5.09 cm 3 Gas Law Problems b A gas occupies 7.84 cm 3 at 71.8 kPa & 25°C. Find its volume at STP. P  T  VV

25. GIVEN: P 1 = 765 torr T 1 = 23°C = 296K P 2 = 560. torr T 2 = ? WORK: P 1 V 1 T 2 = P 2 V 2 T 1 Gas Law Problems b A gas’ pressure is 765 torr at 23°C. At what temperature will the pressure be 560. torr? PP TT (765 torr)T 2 = (560. torr)(296K) T 2 = 217 K = -56°C