How can these characteristics of water be explained?

Question

A-F are the properties of water that I have to use to describe the phenomenon in 1-8. Each letter can be used more than once, and more than one letter can go with each number. Any help?

A) H2O molecules are cohesive; they form hydrogen bonds with each other.

B) H2O molecules are adhesive; they form hydrogen bonds with polar surfaces.

C) Water is a liquid at normal physiological temperatures.

D) Water has a high specific heat.

E) Water has a high heat of vaporization.

F) Water's greatest density occurs at 4C.

1) During winter, air temps in the northern U.S. can remain below 0C for months, but fish and other animals living in the lakes survive.

2) Many substances--like salt and sucrose--dissolve quickly in water.

3) When 25 mL of water are poured into a grad. cylinder, a meniscus forms at the top of the water column.

4) Sweating and the evaporation of sweat from the body surface help reduce a human's body temperature.

5) A bottle has a liquid mix of equal parts water and mineral oil. When shaken vigorously and placed on a table, the mixture separates into layers of oil over water.

6) Water drops that fall on a surface tend to form rounded drops or beads.

7) Water drops that fall on a car tend to bead or round up more after the car is polished/wax than before it is polished/waxed.

8) If the edge of a paper towel is touched to a drop of colored water, the water will move up into/be absorbed by the towel.

Sorry for such a long question. Thanks in advance.

Answer 1

Billy S is right, but the answer to question 1 is F. Because water has the greatest density at 4 degrees celsius, the warmer water (i.e. that at 4 degrees) sinks to the bottom of the lake. Even though the water near the surface is at or below freezing (0 degrees) the fish can survive by living in the water at the bottom of the lake.  

Answer 2

I can help with most of these:

2) B

Water is a strongly polar molecule. The oxygen atom is very electronegative and instead of sharing electrons equally with the Hydrogens it instead pulls the shared electrons towards itself. The electrons in a O-H bond reside mostly on the Oxygen atom, thus the oxygen part of the molecule is strongly negative. The Hydrogen atoms are effectively positive. Since the shape of a water molecule is bent, this means you end up with a effectively positive and effectively negative end.

The +ve end of the molecule will interact strongly with -ve ions or with -ve regions on other polar molecules, and the -ve end of the water will do the same with +ve ions or +ve regions of other polar compounds. In this way water is able to very readily solvate ionic compounds and polar compounds (dissolve them).

Within water itself, the attractions between the H of one O-H in one molecule and the O of another molecule are so strong that they are called hydrogen bonds. H bonding only occurs with H bonded to N, O or F and the corresponding N, F or O in adjacent molecules.

3) A) and B)

The water molecules that are in contact with the glass form strong attractions with the surface molecules of the measuring cylinder. The attraction is so strong that the water molecules will actually creap up the sides of the vessel. Because the water molecules are also strongly attracted to each other, the molecules creaping up the side will also pull up surrounding water molecules. So you get the classic meniscus shape. Gravity kick in in the middle and holds the centre down. In tubing of very small diameter (capillary tubes) the effect is such that the attractive forces between the glass and water pull the outside molecules up the walls, and the attractive forces between water pull the rest of the water up with them, so water moves up the tube under it's own steam (capillary action)

4) E - when water evaporates it requires a lot of heat. Some of the heat required to evaporate sweat from your body comes from your body, so you are loosing heat to evaporate sweat. So it cools you down.

5). A) Oil is non-polar  and water molecules are not attracted to non-polar moleculaes. In this instance, the water molecules will only form attraction with each other and so will not mix with the oil.

6.) A) The surface must not contain any charged or polar molecules for the water to interact with. as in 5, the water molecules will only be interacting with themselves. The reason why they for beads is because a sphere is the shape that presents the least surface area to volume ratio of any shape. All the water molecules are forming internal attraction with each other and presenting the non-polar surface with as little area as they can. (kind of the opposite to how they will spread out over a polar surface because they are attracted to it)

7) A. Wax is non-polar. Water wants to touch as litte area of the non-polar surface as it can, as in 6.

8). A and B

This is a little like 2. Inside the paper towel the are spaces and channels that more or less act as capillaries. The water is initally draw into to towel by attractive forces between paper and water, but because the water molecules are also attracted to each other then each water molecule that moves into the towel will pull another water molecule in after it, and so on.

Capillary action is also very relevant in the (phloem or xylem - forget which is which) of plants. It is what helps huge trees pull water from the roots all the way up to the leaves.

1) most likely D - not sure I can really provide a good explaination though, sorry

I hope this helps, some of them are pehaps not very eloquent.