2.5 Study Guide

Question 1

Define cohesion

Answer 1

Attraction between molecules of the same substance

Question 2

Define adhesion

Answer 2

Attraction between molecules of different substances

Question 3

Define solvent

Answer 3

The substance that dissolves the solute

Question 4

Define specific heat

Answer 4

The heat required to raise the temperature of the unit mass of a given substance by a given amount

Question 5

Define solvent

Answer 5

The substance that dissolves the solute

Question 6

Define specific heat

Answer 6

The heat required to raise the temperature of the unit mass of a given substance by a given amount

Question 7

Define heat of vaporization

Answer 7

The amount of heat required to convert unit mass of a liquid into the vapor without a change in temperature.

Question 8

Define concentration

Answer 8

The amount of particles in a particular area

Question 9

Define pH

Answer 9

The concentration of hydrogen ions in a solution

Question 10

Define pOH

Answer 10

Measure of hydroxide ion concentration

Question 11

Define hydroxide ion

Answer 11

A water molecule that has lost a proton; OH-

Question 12

Define hydronium ion

Answer 12

Consists of a hydrogen ion attached to a water molecule (H3O+)

Question 13

Define acid

Answer 13

A substance that increases the hydrogen ion concentration of a solution.

Question 14

Define base

Answer 14

A substance that reduces the hydrogen ion concentration of a solution

Question 15

List 5 properties of water

Answer 15

1. Polar and Non-polar
2. High heat capacity
3. Cohesive and Adhesive
4. Water is a solvent
5. Water is less dense as a solid then as a liquid

Question 16

Explain how water’s polarity or ability to make hydrogen bonds gives it each property.

Answer 16

As a result of water’s polarity, each water molecule attracts other water molecules because of the opposite charges between them, forming hydrogen bonds. Water also attracts, or is attracted to, other polar molecules and ions, including many bio-molecules, such as sugars, nucleic acids, and some amino acids.

Question 17

Examples of why each property is important to living things.

Answer 17

1. Water is polar.- Water molecules are polar, with partial positive charges on the hydrogen molecules, a partial negative charge on the oxygen, and a bent overall structure. This is because oxygen is more electronegative, meaning that it is better than hydrogen at attracting electrons.
2. Water is a solvent.- Water has the unique ability to dissolve many polar and ionic substances. This is important to all living things because, as water travels through the water cycle, it takes many valuable nutrients along with it
3. Water has a high heat capacity.- It takes a lot of energy to raise the temperature of a certain amount of water by a degree, so water helps with regulating temperature in the environment. For example, this property allows the temperature of water in a pond to stay relatively constant from day to night, regardless of the changing atmospheric temperature.
4. Water has high heat of vaporization.- Humans use water’s high heat of vaporization to cool off. Water is converted from its liquid form to steam when the heat of vaporization is reached.
5. Water has cohesive and adhesive properties.- Water molecules have strong cohesive forces due to their ability to form hydrogen bonds with one another. Cohesive forces are responsible for surface tension, the tendency of a liquid’s surface to resist rupture when placed under tension or stress.
6. Water is less dense as a solid than as a liquid.- As water freezes, the molecules form a crystalline structure that spaces the molecules further apart than in liquid water. This property is important, as it keeps ponds, lakes, and oceans from freezing solid and allows life to continue to thrive under the icy surface.

Question 18

Calculate pH, [H3O+], [OH-], pOH when given one of the four variables

Answer 18

pH = -log[H₃O⁺]
[H3O+]=antilog(−pH)=10−pH
[OH-] = 10^-pOH
pOH=-log[OH-]

Question 19

Compare the concentrations of [H3O+] and [OH-] of solutions with two different pHs

Answer 19

If the concentration of H3O+ is 1.0x10-13 and the concentration of OH- is 1.0x10-1, they both have a pH of 13. This is because H3O+ and OH- are inversely related to eachother. Another example of this is if the concentration of H3O+ is 1.0x10-1 and the concentration of OH- is 1.0x10-13, they still have the same pH which is 1.

Question 20

Decide whether a solution is an acid, base, or neutral when given either pH, [H3O+], [OH-], or pOH

Answer 20

pH of 6 = acid (less than 7 is acid, more than 7 is base)
pOH of 12 = acid (inverse with pH)
H3O+ is an acid
OH- is a base