2.3.2 Water: Adhesion, Cohesion, and a Solid That Floats

Question 1

note

Answer 1

• The polarity of water results in several properties that are fundamental to life. These properties include adhesion, cohesion, water’s high specific heat, and the ability of ice to float.

Question 2

adhesion

Answer 2

• Water is also able to cling to other materials

because of its ability to hydrogen-bond.

Question 3

cohesion

Answer 3

• Water can cling to other water molecules

because of its ability to hydrogen-bond.

Question 4

surface tension

Answer 4

• results from the cohesion of water. Water molecules on the surface of water experience a force because of hydrogen bonding between each other and the water
  molecules below. The net force that acts on water molecules on the surface forms a “film” of tightly packed molecules.

Question 5

turnover

Answer 5

• When the water on the surface approaches 4 degrees

Celsius it begins to sink, drawing up the warmer water on the bottom.

Question 6

The surface tension of water is caused by

Answer 6

• the downward net cohesive force on the water molecules at the surface

Question 7

Unlike most liquids which steadily decrease in density as they increase in temperature, water exhibits unusual behavior because of the hydrogen bonds between water molecules. Place the following in order of increasing density: ice, water at 4°C, water at 20°C.

Answer 7

• ice, water at 20°C, water at 4°C

Question 8

Ice is less dense than liquid water because

Answer 8

• the open crystal structure of ice.

Question 9

Water at 4°C occupies ________ volume than it does at 0°C, and water is _______ dense at 4°C than it is at 0°C.

Answer 9

• less, more

Question 10

Some insects are able to walk on water. This is partially a result of the high __________ of water caused by the __________ between water molecules.

Answer 10

• surface tension, hydrogen bonds

Question 11

Water can move through the xylem (circulatory tissue) of plants, apparently in defiance of gravity. What property of water makes it able to do this?

Answer 11

• Water molecules can both hydrogen bond with themselves and with other materials

Question 12

A muddy stream flows from under a glacier and into a lake. The stream water is 4°C. The lake water has warmed in the summer sun to about 20°C on top. What will happen to the stream water as it enters the lake?

Answer 12

• The muddy stream water will flow along the bottom of the lake