Biochemistry___Lesson-4___Chapter 2.10 thru 2.13

Question 1

Molecules of the same kind sticking together.

Answer 1

Cohesion

Question 2

Different types of molecules sticking together.

Answer 2

Adhesion

Question 3

A measure of how difficult it is to break the surface of a liquid.

Answer 3

Surface Tension

Question 4

The energy associated with the random movement of atoms and molecules.

Answer 4

Thermal Energy

Question 5

The average speed of molecules in a body of matter.

Answer 5

Temperature

Question 6

Transfer of thermal energy from a warmer to a cooler body of matter.

Answer 6

Heat

Question 7

Resists changes in temperature.

Answer 7

Temperature Buffer

Question 8

When a substance evaporates, the surface of the liquid that remains behind cools down.

Answer 8

Evaporative Cooling

Question 9

A liquid consisting of a uniform mixture of two or more substances.

Answer 9

Solution

Question 10

The liquid in a solution that dissolves other substances.

Answer 10

Solvent

Question 11

The substance that is dissolved in a solution.

Answer 11

Solute

Question 12

A solution in which water is the solvent.

Answer 12

Aqueous Solution

Question 13

Four water properties allow water to move up a plant!!! Draw water molecules hydrogen bonded to each other (cohesion) to form both surface tension and a column down a cellulose tube. Also draw the water hydrogen bonded to the tube (adhesion). Make a deep concave meniscus due to water molecules that leave due to evaporative cooling.

Answer 13

Question 14

Draw a graph describing the movement of thermal energy.

Question 15

Draw ice and liquid water to compare their relative densities.

Answer 15

Question 16

Draw an aqueous solution of sodium chloride.

Answer 16

Question 17

Are you warmer when you run or when you move slowly like walking? When molecules become colder, are they moving faster or slower?

Answer 17

You are warmer when you run, which is analogous to molecules moving faster when warm and slower when cold.

Question 18

You and a teammate are moving towards each other; is it easier to shake hands if you are walking towards each other or sprinting towards each other? When water molecules move slower, does it become easier or harder for them to form hydrogen bonds?

Answer 18

It would be easier to shake hands when moving slower, which is analogous to it being easier for water molecules to form hydrogen bonds with each other when they are moving slower.

Question 19

Water is a temperature buffer, which means that it will resist a change in temperature. When water molecules form hydrogen bonds, do they release heat or absorb heat?

Answer 19

When it is cold water molecules move slower (remember the running analogy), when water molecules move slower, they can shake hands, i.e., they can form hydrogen bonds. Buffering is a resistance to change, so if hydrogen bonds form when it is cold, then hydrogen bonds must give off heat, which is the opposite of cold and would thus resist being cold.

Question 20

Water is a temperature buffer, which means that it will resist a change in temperature. When the air is warmer than the ocean, the ocean will absorb the extra heat, but the water molecules will only move a little faster. If the heat was not used to make the water molecules move faster, then what was the heat used for?

Answer 20

The heat was used to break hydrogen bonds.

Question 21

Explain the role of hydrogen bonds in the following water properties: Cohesion

Answer 21

Cohesion is when two molecules of the same kind stick together. Water shows cohesion because the partially positive hydrogen of one water molecule will stick to the partially negative oxygen of a different water molecule, and that sticking of partially positive hydrogen to other atoms of opposite charge is the definition of a hydrogen bond.

Question 22

Explain the role of hydrogen bonds in the following water properties: Adhesion

Answer 22

Adhesion is when two different types of molecules stick together. Water shows adhesion because it will stick to any other type of molecule that has a partially negative charge through a hydrogen bond with the partially positive hydrogen of water and conversely any other molecule with a partially positive hydrogen will form a hydrogen bond through the partially negative oxygen of water.

Question 23

Explain the role of hydrogen bonds in the following water properties: Surface Tension

Answer 23

The network of water molecules at the surface of water all stick to each other by hydrogen bonds (cohesion). For an object to break the surface of the water it must first break all the hydrogen bonds. A water strider insect exerts less force than the surface tension and thus it can walk on the surface of water.

Question 24

Explain the role of hydrogen bonds in the following water properties: Heat Buffer

Answer 24

When the air is cold some heat will be transferred from the ocean to the air, which will cause the water molecules to slow down a little, which will cause them to form more hydrogen bonds, which will result in a large release of heat to the air, which will warm the air up. Thus, cold air triggers the ocean to release heat and warm the air up.

When the air is hot, heat will be absorbed by the ocean, which will cool the air down, the absorbed heat will be mostly used to break hydrogen bonds and thus the ocean will only heat up a little.

Question 25

Explain the role of hydrogen bonds in the following water properties: Evaporative Cooling

Answer 25

Your temperature is the average speed of all your molecules. When you sweat, your fastest molecules have left your body, and the remaining molecules now have a lower average speed and thus you have a lower temperature. It is analogous to the 10 fastest runners transferring out of your school. If you took the average speed of the student body before and after the 10 students left, you would see that the average decreased when they left. A lot of energy must be absorbed to break the hydrogen bonds and allow the water to escape with that energy.

Question 26

Explain the role of hydrogen bonds in the following water properties: Ice Floats

Answer 26

In ice, each water molecule is locked a certain distance from its 4 water-molecule-partners by hydrogen bonds, but in liquid water the hydrogen bonds continually break and reform, which allows the water molecules to get closer to each other, thus giving liquid water a greater density (more water molecules per given volume) than ice, and because is less dense than liquid water it floats.

Question 27

Explain the role of hydrogen bonds in the following water properties: Water is a universal solvent.

Answer 27

A solution is a liquid mixture of 2 or more substances. One of the substances has most of the molecules and is called the solvent, and the other is the solute. For example, if you make a solution of water and glucose, then most of the molecules are water molecules (water is the solvent) and the glucose molecules are the solutes. Water is polar, which means it has a partially positive end and a partially negative end. This makes it a great solvent because a solute with any type of charge will be surrounded by the opposite charge of water molecules. For example, glucose would be surrounded by hydrogen bonds to water.