Chapter 3 Key Terms

Question 1

acid

Answer 1

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

Question 2

acid precipitation

Answer 2

Rain, snow, or fog that is more acidic than pH 5.6.

Question 3

adhesion

Answer 3

The attraction between different kinds of molecules.

Question 4

aqueous solution

Answer 4

A solution in which water is the solvent.

Question 5

base

Answer 5

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

Question 6

buffer

Answer 6

A substance that consists of acid and base forms in a solution and that minimizes changes in pH when extraneous acids or bases are added to the solution.

Question 7

calorie (cal)

Answer 7

The amount of heat energy required to raise the temperature of 1 g of water by 1°C; also the amount of heat energy that 1 g of water releases when it cools by 1°C. The Calorie (with a capital C), usually used to indicate the energy content of food, is a kilocalorie.

Question 8

Celsius scale

Answer 8

A temperature scale (°C) equal to 5/9 (°F - 32) that measures the freezing point of water at 0°C and the boiling point of water at 100°C.

Question 9

cohesion

Answer 9

The binding together of like molecules, often by hydrogen bonds.

Question 10

colloid

Answer 10

A mixture made up of a liquid and particles that (because of their large size) remain suspended in that liquid.

Question 11

evaporative cooling

Answer 11

The property of a liquid whereby the surface becomes cooler during evaporation, owing to a loss of highly kinetic molecules to the gaseous state.

Question 12

heat

Answer 12

The total amount of kinetic energy due to molecular motion in a body of matter. Heat is energy in its most random form.

Question 13

heat of vaporization

Answer 13

The quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state.

Question 14

hydration shell

Answer 14

The sphere of water molecules around each dissolved ion.

Question 15

hydrogen ion

Answer 15

A single proton with a charge of +1. The dissociation of a water molecule (H2O) leads to the generation of a hydroxide ion (OH-) and a hydrogen ion (H+).

Question 16

hydrophobic

Answer 16

Having an aversion to water; tending to coalesce and form droplets in water.

Question 17

hydrophilic

Answer 17

Having an affinity for water.

Question 18

hydroxide ion

Answer 18

A water molecule that has lost a proton.

Question 19

joule (J)

Answer 19

A unit of energy: 1 J = 0.239 cal; 1 cal = 4.184 J.

Question 20

kilocalorie (kcal)

Answer 20

A thousand calories; the amount of heat energy required to raise the temperature of 1 kg of water by 1°C.

Question 21

kinetic energy

Answer 21

The energy of motion, which is directly related to the speed of that motion. Moving matter does work by imparting motion to other matter.

Question 22

molarity

Answer 22

A common measure of solute concentration, referring to the number of moles of solute per liter of solution.

Question 23

mole (mol)

Answer 23

The number of grams of a substance that equals its molecular weight in daltons and contains Avogadro’s number of molecules.

Question 24

molecular mass

Answer 24

The sum of the masses of all the atoms in a molecule; sometimes called molecular weight.

Question 25

pH

Answer 25

A measure of hydrogen ion concentration equal to –log [H+] and ranging in value from 0 to 14.

Question 26

polar molecule

Answer 26

A molecule (such as water) with opposite charges on opposite sides.

Question 27

solute

Answer 27

A substance that is dissolved in a solution.

Question 28

solution

Answer 28

A liquid that is a homogeneous mixture of two or more substances.

Question 29

solvent

Answer 29

The dissolving agent of a solution. Water is the most versatile solvent known.

Question 30

specific heat

Answer 30

The amount of heat that must be absorbed or lost for 1g of a substance to change its temperature by 1°C.

Question 31

surface tension

Answer 31

A measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension because of the hydrogen bonding of surface molecules.

Question 32

temperature

Answer 32

A measure of the intensity of heat in degrees, reflecting the average kinetic energy of the molecules.