1. Phases of Matter Properties of a Gas Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology

2. Properties of Gases  Reading Assignment: Zumdahl, Chapter 5.1-5.3  This lecture introduces the interrelated dependence of moles, temperature, pressure and volume of a confined gas.  Based on assumptions of ideal gas behavior, these parameters when combined form the ideal gas equation, PV=nRT.

3. Phases of Matter  Gases  Liquids  Solids  Plasma

4. Gases Large intermolecular distances, compared to molecular size No long or short range structural order

5. Gases Mix together in any proportions Intermolecular collisions are elastic -- energy is transferred through collisions

6. Liquids Small intermolecular distances -- molecules are "touching" Molecules may be ordered with respect to each other over a short range, but no long range structural order Energy is transferred through molecular vibration

7. Liquids May or may not be miscible

8. Liquids Aqueous solutions are like liquids, except solute is surrounded by solvent

9. Solids Small intermolecular distances -- molecules are "touching" Long and short range structural order in crystalline solids Energy is transferred through molecular vibration

10. Solids Amorphous solids have less structural order

11. Solids Very limited miscibility while remaining in the solid state

12. Solids Frozen solutions are possible and called solid solutions

13. Plasma  High energy state in which all molecules are broken into constituent atoms, and most or all of the electrons are stripped from the atom  Very high temperature (  10 6 K), condensed, gas-like phase consisting of nuclei and electrons

14. Plasma  Nuclei mix together in any proportions  Applications occur in a few analytical detection techniques and nuclear reactions  Not involved in typical chemical reactions

15. Physical Properties of Matter  Temperature  Pressure  Volume  Moles

16. Temperature  Temperature is a measure of molecular motion: vibration, rotation and translation  Gases move at high velocity (> 1000 m·sec –1 )  Common units: Celsius (°C), Fahrenheit (°F)

17. Temperature  Absolute units: Kelvin (K), Rankine (°R)  0.00 °C = 273.15 K = 32.00 °F = 491.67 °R  100.00 °C = 373.15 K = 212.00 °F = 671.67 °R  Isothermal - constant temperature

18. Pressure Due to molecules hitting the surface Force per unit area

19. Pressure What do you know about the pressure in a balloon?

20. Pressure Within a closed container with a flexible or moveable barrier, the external forces pushing on the surface of the container containing the gas are equal to the pressure of the trapped gas pushing out.

21. Barometer mercury vacuum What forces determine the height of the mercury in the glass tube?

22. atmospheric pressure What forces determine the height of the mercury in the glass tube? Barometer

23. 760 mm  30 in How much pressure does the atmosphere exert?  Hg = 13.6 g· cm –3 = 0.490 lb·in –3 1.03 kg· cm –2 = 14.7 lb· in –2

24. Barometer  H 2 O= 1.0 g· cm –3 33 feet What is different if water is used as the fluid, rather than mercury?

25. Pressure  Common units: lbs·in –2, atmospheres (atm), mm Hg, torr, pascals (N·m –2, Pa)  1.00 atm = 14.7 lbs·in –2 = 760 mm Hg = 760 torr = 1.013 x10 5 Pa

26. Pressure  The actual atmospheric pressure is a function of the weather (high or low pressure) and altitude. Typical Terre Haute pressure is 730-750 mm Hg.  Isobaric - constant pressure

27. Volume  Gases occupy the complete volume to which they are constrained  Liquids and solids occupy a volume corresponding to their mass and density  Isochoric - constant volume

28. Moles  A counting unit for the number of molecules being considered

29. Physical Laws of Gases  Boyle's Law  Charles' Law  Avogadro's Law  Ideal Gas Law

30. Boyle's Law  P·V = constant isothermal constant amount of gas volume pressure What does a plot of this relationship look like?

31. Charles' Law VTVT isobaric constant amount of gas volume temperature What does a plot of this relationship look like? What does the y-intercept indicate?

32. Avogadro's Law VnVn isobaric isothermal volume moles of gas What does a plot of this relationship look like?

33. Gas Laws volume pressure Boyle volume temperature Charles volume moles of gas Avogadro V  1/PV  TV  n V  nT P

34. Ideal Gas Law  P·V  n·T  PV = nRT where R = ideal gas constant = 0.08206 L·atm·mol –1 ·K –1

35. Boyle's Law  P·V = constant isothermal constant amount of gas volume pressure How will this plot change if the same number of moles of gas are at a higher temperature?

36. Common Gases Room Temperature, One Atmosphere Pressure  Monatomic: He, Ne, Ar, Kr, Xe, Rn  Polyatomic Elements: N 2, O 2, O 3, F 2, Cl 2 Compounds: CO, CO 2, NO, N 2 O, NO 2, N 2 O 4, N 2 O 5, CH 4, C 2 H 6, C 2 F 4, etc.

37. Atmospheric Composition  Dry air 78% N 2, 21% O 2, 1%Ar  Normal air N 2, O 2, Ar, 0.03% CO 2, 1.6% H 2 O