Chapter 10 - Gases



Chapter 13 - States of Matter Homework

Gases and Intermolecular Forces: Read p. 385-395 and answer the following questions:

1. What are the three assumptions of the Kinetic Molecular theory?

2. What is temperature the average measure of?

3. What is the mathematical formula for Kinetic Energy (define each of the variables in the equation)

4. What is the definition of Pressure?

5. What is the name of the device used to measure atmospheric pressure?

6. Explain how the mercury in a barometer is kept at 760 mm above the surface.

7. A Pascal (Pa) is the metric unit of pressure. But the Pascal is derived from two other SI base units. Write the SI base units and set them equal to one Pa. (see p. 390).

8. A Pascal is only one way to measure pressure. At sea level, there is a pressure of 1 atm. Look at table 13-1 on p. 390 and write the pressure at sea level for the following units:

atm________ psi _________ mmHg ________ torr _________ Pa ________ kPa _________

9. At sea level, how many POUNDS of air pressure are on each square inch of your body (hint, look at one of the units from 13-1)

10. Do this conversion: Mount Everest has a pressure of 33.6 kPa. Convert this pressure into atmospheres (atm). (Hint: Like any conversion, you start with what you know - 33.6 kPa - and then you make a times sign and draw a line. The denominator is the unit you "know". The numerator is the unit you want.)

11. What is Dalton's law of partial pressure?

12. Do practice problem #4 p. 392

13. Do practice problem #5 p. 392

14. Do practice problem #6 p. 392

15. Look at figure 13-7 on p. 392. When you collect gas over water, there are actually TWO gases in there. One is the gas(es) you are collecting. The other is _______________

16. What is water's vapor pressure (in kPa) if it is at a temperature of 20oC?

17. Think about it: What do you think the vapor pressure of water is at 100oC - water's boiling point (in kPa)?

18. How could you make water boil at a temperature of 20oC?

19. Think about it: Does boiling mean that the liquid must be REALLY HOT? Explain why or why not.

20. Name the three INTRAmolecular forces.

21. Name the three INTERmolecular forces.

22. Which is stronger: INTRA or INTER molecular forces. Which one requires more energy to break and create

23. What is a temporary dipole? Give an example of a molecule held together by a temporary dipole.

24. Molecules held together using temporary dipoles (dispersion forces - or London Forces as they are sometimes called) tend to be what phase of matter at room temperature. Solid, liquid or gas (circle one)

25. Why are halogens Bromine and Iodine liquids and solids at room temp, but Fluorine and Chlorine are gases?

26. Why does water have a higher boiling point than Methane and Ammonia?

Phase Changes: Read p. 404-409

27. Boiling, freezing, melting, vaporizing…. These phase changes are all a result of breaks in

a. INTERmolecular bonds b. INTRAmolecular bonds

28. Boiling, freezing, melting, vaporizing….. These are all: a. chemical changes b. physical changes

29. Look at figure 13-22 on p. 404: What is the term used when a solid turns directly into a gas without first becoming a liquid?

30. Why does it take less energy to melt ice than it does table salt? (for example, an ice cube left out on the table will melt with the regular energy of room temperature, but salt will not melt under these circumstances)

31. Which is stronger: Hydrogen bonds or Ionic Bonds (look at your answer to #30) for help.

32. What happens at the melting point of a solid (describe the process).

33. For the following phase changes, state if energy is RELEASED (exothermic) or if energy is ABSORBED (endothermic) - "RE" for released, "AB" for absorbed

Melting _____ Freezing _____ Boiling ____ Condensing _____ Subliming _____ Vaporizing _____

34. When vaporization occurs ONLY at the surface of the liquid, the process is called ___________

35. When vaporization occurs throughout all parts of the liquid, the process is called ____________

36. Why does sweating help to cool your body?

37. What is the vapor pressure? Is it temperature dependent?

38. What happens when a liquid's vapor pressure reaches the outside air pressure?

39. Is it possible to heat a liquid to where its vapor pressure is more than the outside air pressure yet it still doesn't boil? How can this madness be done? Is it dangerous?

40. Name four substances that sublime:

41. Why do ice cubes shrink in the freezer if left for a long period of time?

42. How do you make freeze-dried food?

Look at the phase diagrams for water and CO2 on p. 409 to answer these questions

43. What's so special about the triple point of these graphs?

44. 1 ATM represents sea level on the graphs. If you were to go into the mountains, obviously, the pressure would change. But would it be ABOVE 1 atm, or BELOW 1 atm?

45. What happens to the freezing point of WATER in the mountains?

a. is above 0oC b. is below 0oC c. is 0oC

46. What happens to the boiling point of WATER in the mountains?

a. is above 100oC b. is below 100oC c. is 100oC

47. If you were to hard boil an egg in boiling water in the mountains would it take

a. longer to get hard boiled than at sea level b. shorter time c. same time

48. If you were to FRY an egg in a pan in the mountains would it take

a. longer to fry b. shorter time to fry c. same time

49. What is the sublimation point of CO2 at 1 atm of pressure?

50. What is the "street name" for CO2 when it is in its solid form?

51. If you INCREASE the pressure on water, what happens to its melting point

a. it increases b. it decreases c. it stays the same

52. If you INCREASE the pressure on CO2, what happens to its melting point

a. it increases b. it decreases c. it stays the same

53. If you squeeze an ice cube (and pretend your hands are 0oC), will it melt faster or slower?

54. Look back at question #10 (the air pressure on Mt. Everest). Estimate the boiling point of water on Mt. Everest using the phase diagram for Water. (Just FYI: Hot coffee is about 70oC).

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