Chapter 3 Water and Life

Question 1

Acid

Answer 1

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

Question 2

adhesion

Answer 2

The clinging of one substance to another, such as water to plant cell walls by means of hydrogen bonds.

Question 3

aqueous solution

Answer 3

A solution in which water is the solvent.

Question 4

Base

Answer 4

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

Question 5

Buffer

Answer 5

A solution that contains a weak acid and its corresponding base. A buffer minimizes changes in pH when acids or bases are added to the solution.

Question 6

calorie (cal)

Answer 6

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 7

cohesion

Answer 7

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

Question 8

evaporative cooling

Answer 8

The process in which the surface of an object becomes cooler during evaporation, a result of the molecules with the greatest kinetic energy changing from the liquid to the gaseous state.

Question 9

Heat

Answer 9

Thermal energy in transfer from one body of matter to another.

Question 10

heat of vaporization

Answer 10

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

Question 11

hydration shell

Answer 11

The sphere of water molecules around a dissolved ion.

Question 12

hydrogen ion

Answer 12

A single proton with a charge of 1+. The dissociation of a water molecule ( H 2 O ) leads to the generation of a hydroxide ion (OH–) and a hydrogen ion (H+); in water, H+ is not found alone but associates with a water molecule to form a hydronium ion.

Question 13

hydronium ion

Answer 13

A water molecule that has an extra proton bound to it; H3O+, commonly represented as H+.

Question 14

hydrophilic

Answer 14

Having an affinity for water.

Question 15

hydrophobic

Answer 15

Having no affinity for water; tending to coalesce and form droplets in water.

Question 16

hydroxide ion

Answer 16

A water molecule that has lost a proton; OH–.

Question 17

joule (J)

Answer 17

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

Question 18

kilocalorie (kcal)

Answer 18

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

Question 19

kinetic energy

Answer 19

The energy associated with the relative motion of objects. Moving matter can perform work by imparting motion to other matter.

Question 20

molarity

Answer 20

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

Question 21

mole (mol)

Answer 21

The number of grams of a substance that equals its molecular or atomic mass in daltons; a mole contains Avogadro’s number of the molecules or atoms in question.

Question 22

molecular mass

Answer 22

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

Question 23

ocean acidification

Answer 23

The process by which the pH of the ocean is lowered (made more acidic) when excess CO 2 dissolves in seawater and forms carbonic acid ( H 2 CO 3 ) .

Question 24

ph

Answer 24

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

Question 25

polar covalent bond

Answer 25

A covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive.

Question 26

polar molecule

Answer 26

A molecule (such as water) with an uneven distribution of charges in different regions of the molecule.

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 1 g of a substance to change its temperature by 1°C.

Question 31

surphace 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 in degrees of the average kinetic energy (thermal energy) of the atoms and molecules in a body of matter.

Question 33

thermal energy

Answer 33

Kinetic energy due to the random motion of atoms and molecules; energy in its most random form. See also heat.