Are these adhesive or cohe sive forces at work by zlPmEyM


									43. Mercury forms a convex meniscus with glass rather          tions in global temperatures be more or less pronounced?
than the concave meniscus shown in Figure 8.18. What           59. Bermuda is close to North Carolina, but unlike North
does this tell you about the cohesive forces between mer-      Carolina, it has a tropical climate year round. Why?
cury atoms versus the adhesive forces between mercury
                                                               60. If the winds at the latitude of San Francisco and
atoms and glass? Which forces are stronger?
                                                               Washington, D.C., were from the east rather than from
                                                               the west, why might San Francisco be able to grow cherry
                                                               trees and Washington, D.C., palm trees?
                                                               61. Why is it that in cold winters a large tub of liquid
                                                               water placed in a farmer's canning cellar helps prevent
                                                               canned food from freezing?
            Convex meniscus       Concave meniscus
44. Would you expect the surface tension of water to           62. Why do ice cubes get smaller when left in the freezer
increase or decrease with temperature? Defend your             for a long time?
answer.                                                        The following diagram describes the phase of water rela-
45.  Dip a paper clip into water and then slowly pull it       tive to temperature and pressure. Use this diagram for
upward to the point where it is nearly free from the sur-      questions 74-77.
face. You'll find that for a short distance, the water is      Water Phase Diagram
brought up with the metal. Are these adhesive or cohe-
sive forces at work?
46. A thin film of fresh water can be made to stretch
across a small wire loop with a diameter of about
1 centimeter. At larger diameters, however, the film col-
lapses into a water drop. If water's surface tension were
greater, might greater diameters of a thin film be
47. A duck can come out of the water with its feathers
already perfectly dry. How can this be? Why are oil spills
particularly devastating for sea birds?
                                                               63. At which point is water boiling?
48. Why do bubbles in boiling water get larger as they
                                                               64. At which point does water exist in all three phases?
rise to the surface?
49. Where is the boiling point of water the greatest: at the   65. What happens to the melting temperature of water
bottom of a pot of water or just below the surface? Why?       as pressure is increased? What happens to water's boiling
                                                               temperature as pressure is increased?
50. You can determine wind direction by wetting your
finger and holding it up in the air. Explain.                  66. Is it possible for ice to transform to water vapor with-
                                                               out ever becoming liquid?
51. Why does wetting a cloth in a bucket of cold water
and then wrapping the wet cloth around a bottle produce
a cooler bottle than placing the bottle directly in the
bucket of cold water?
52. A lid on a cooking pot filled with water shortens
both the time it takes the water to come to a boil and the
time the food takes to cook in the boiling water. Explain
what is going on in each case.
53. Maple syrup is made by concentrating the sap of the
sugar maple tree. Why does is take so much energy to
make maple syrup?
54. Describe the motion of two magnetic marbles as they
roll closer to each other and then come into contact. What
happens to two water molecules after they come together
to form a hydrogen bond—do they vibrate more rapidly
or less rapidly?
55. Why does liquid water have such a high specific heat?
56. What would happen to the oceans if the atmosphere
suddenly disappeared?
57. Which has a higher specific heat: fresh water or
ocean water?
58. If Earth's oceans were fresh water, would fluctua-

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