Unit 7 Test: Gases



Unit 7 (Chapter 14) – The Behavior of Gases. Name: __________________________

Questions:

1. You should use a smartphone or computer in order to answer the question, “What is a gas?” You could find a very good answer by going to these websites: ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

2. You should read pp 413 – 417 to answer the next several questions; you could use another sheet of paper if you prefer.

3. Why is a liquid or a solid harder to compress than a gas? ______________________________________________________________________________________________________________________________________________________________________

4. How does the gas propellant move when an aerosol can is used?

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5. Why does air escape from a tire when the tire valve is opened? (p. 416: a tire is a “sealed container” until the valve is opened).

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6. Why does the pressure inside a container of gas decrease if gas is removed from the container?

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7. If the amount of gas in an unflexible container is doubled, by what factor (x2, x3, x4…?) is the pressure increased?__________________________________________________________

8. If the amount of gas in an unflexible container is tripled, by what factor (x2, x3, x4…?) is the pressure increased?________________________________________________________________

9. If 2 moles of gas is added to a container that already holds 1 mole of gas, by what factor (x2, x3, x4…?) is the pressure increased?_____________________________________________________

10. If 3 moles of gas is added to a container that already holds 1 mole of gas, by what factor (x2, x3, x4…?) is the pressure increased? ____________________________________________________

11. If the volume of a gas is halved while the temperature remains constant, by what factor does the gas pressure change: (x ½, x 2, x ¼, x 4)? Select one. _________________________________

12. If the volume of a gas is increased from 4 liters to 32 liters, while the temperature remains constant, by what factor does the gas pressure change? (x ½, x ¼, x [pic] x 2, x 4, x 8)? Select one.______

13. If the volume of a gas is 2.4 liters at a pressure of 14.1 kPa, what volume will the gas occupy at 84.6 kPa (which is 6 x the original pressure)? _______________________________________

14. Which of these changes would cause an increase in the pressure of a contained gas? (select 1 or more of the following):

-volume is increased -more gas is added to the container

-temperature is increased -average kinetic energy of the gas is increased

My selection(s): __________________________________________________________________

15. Describe how a decrease in temperature affects the speed of gas particles within a closed container.

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16. Describe how a decrease in temperature affects the amount of force gas particles exert on the walls of their container.

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17. What should happen to the volume, the average kinetic energy, and to the pressure of gas inside a balloon if it were taken out of a refrigerator and placed in a warm room?

Volume: __________________________________________________________________________

Average kinetic energy: ______________________________________________________________

Pressure: __________________________________________________________________________

While you are learning about the behavior of gases, it should always be assumed that the gas is contained securely within a vessel (unless otherwise stated), so that none of the particles of the gaseous substance are able to leak out. In other words, the “amount” (# of atoms, molecules, or moles) of the gas is held constant, unless told that a container is opened on purpose.

If/when a question that you are asked omits one of the 3 environmental conditions that affect a gas (pressure, temperature, volume), it is important for you to understand that the missing variable is being held constant. For example, in question # 17, temperature isn’t mentioned in the question….so, temperature is being held constant (and therefore doesn’t affect your answer).

18. If the volume of a container is enlarged, what will happen to the pressure inside the container?

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19. What happens to the temperature of a gas when its volume is expanded?

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20. What happens to the pressure inside a container if the temperature of the gas increases?

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You should read pp 418 – 425 to answer the next several questions; use another sheet of paper if prefer.

21. What does Boyle’s Law state? _________________________________________________________ __________________________________________________________________________________

22. When the amount of gas and the temperature of the gas is held constant, the product of what two variables is also constant? _____________________________________________________________

23. What does Charles’ Law state? _________________________________________________________ __________________________________________________________________________________

24. When the amount of gas and the pressure of the gas is held constant, the ratio of what two variables is also constant? _____________________________________________________________

25. What does Gay-Lussac’s Law state? ________________________________________________ __________________________________________________________________________________

26. When the amount of gas and the volume of the gas is held constant, the ratio of what two variables is also constant? _____________________________________________________________

27. If a balloon is cooled, what happens to the volume of the air in the balloon if the pressure is constant?

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28. If a balloon is cooled, what happens to the pressure of the air in the balloon if the volume remains constant?

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29. As the temperature of a fixed volume of gas decreases, what will the pressure do? _____________ ___________________________________________________________________________________

30. If a sealed syringe is heated, in which direction will the syringe plunger move….in or out? _______

31. When a gas is held at a constant volume, are the Kelvin temperature and volume of the gas directly proportional, or are the Kelvin temperature and volume of the gas indirectly proportional?

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32. Which 3 environmental variables are related to each other when using the “combined gas” law?

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You should read pp 418 – 429 to answer the next several questions; you may use another sheet of paper if you prefer.

33. Which law can be used to calculate the number of moles of a contained gas?

34. What does the ideal gas law allow you to calculate that the other gas laws do not? _________ _________________________________________________________________________________

35. How is the mathematical equation known as the “ideal gas law” usually written? _______________

36. What is the name of the theory that describes and explains the behavior of gases? ____________

37. Does an ideal gas exist? _______________

38. What 2 assumptions does your textbook point out that would be true if an ideal gas were to exist?

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39. Why can a gas condense when compressed and/or cooled? ________________________________

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40. The behavior of real gases differs from ideal gases the most at what 2 conditions?

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41. The behavior of real gases are most similar to ideal gases at what 2 conditions?

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You should read pp 432 – 436 to answer the next several questions; you may use another sheet of paper if you prefer.

42. In a mixture of gases, such as air, how do we determine the total pressure exerted by the gas mixture?

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43. If the atmospheric pressure at the top of Mt. Everest is 1/3rd the pressure at sea level, the partial pressure of oxygen at the top of Mt. Everest is what percent of its pressure at sea level?

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44. If the volume of a container of air is reduced by ½, what happens to the partial pressure of oxygen within the container?

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45. The tendency of molecules to move toward areas of lower concentration, until the concentration is uniform throughout is called?

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46. The escape of a gas through a tiny hole in its container is called? __________________________

47. What does Graham’s Law of effusion state? ____________________________________________ ________________________________________________________________________________

48. In everyday words, what does Graham’s law mean – Will heavier gases move more quickly or more slowly than lighter gases at the same kinetic energy (same temperature)?

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49. Which of the following gases will effuse the most slowly: F2, H2, He, CH4? __________________

50. If you want to keep the balloon inflated the longest, which gas would you choose to put into a large holiday balloon: F2, H2, Ar, He, Ne: ______________________

51. Go to this website and observe how questions similar to the ones you have already answered could be made into flashcards: Research shows that a very effective study method is asking yourself questions and checking your answers immediately – this is far more effective than reading and re-reading “notes”. The multiple choice section of the upcoming test will be very difficult unless you are prepared to answer similar questions to the ones you’ve worked through in this packet. The more you review and answer these questions, the better your grade will be. The content of the multiple choice section of test comes from the questions you have just answered. Review often so that your brain sorts out, makes sense of, and maintains the information.

If you have extra time and are interested, you might want to go to this website and read about the fourth state of matter, called “plasma”. [This is NOT the same plasma as blood plasma. Blood plasma is the fluid of your blood, without the blood cells. The plasma state of matter is what you get when you energize some gases. ]

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