Chapter 3: Water and Life

Question 1

Hydrogen ion

Answer 1

A single proton with a charge of plus one. The dissociation of a water molecule leads to the generation of a hydroxide ion (with a charge of minus one) and a hydrogen ion (with a charge of plus one); in water, the hydrogen ion is not found alone but associates with a water molecule to form a hydronium ion.

Question 2

Hydration shell

Answer 2

The sphere of water molecules around a dissolved ion.

Question 3

Hydrophilic

Answer 3

Having an affinity for water.

Question 4

Mole

Answer 4

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 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

Acid

Answer 6

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

Question 7

Molarity

Answer 7

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

Question 8

PH

Answer 8

A measure of hydrogen ion concentration equal to the negative log of the concentration of hydrogen ions and ranging in value from 0 to 14.

Question 9

Kilocalorie

Answer 9

(kcal) A thousand calories; the amount of heat energy required to raise the temperature of 1 kg of water by 1 degree C.

Question 10

Hydroxide ion

Answer 10

A water molecule that has lost a proton, represented as OH superscript minus.

Question 11

Hydrophobic

Answer 11

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

Question 12

Hydronium ion

Answer 12

A water molecule that has an extra proton bound to it, commonly represented as H superscript plus.

Question 13

Aqueous solution

Answer 13

A solution in which water is the solvent.

Question 14

Heat

Answer 14

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

Question 15

Surface tension

Answer 15

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 16

Base

Answer 16

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

Question 17

Joule

Answer 17

(J) A unit of energy: 1 J equals 0.239 cal; 1 cal equals 4.184 J.

Question 18

Solution

Answer 18

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

Question 19

Evaporative cooling

Answer 19

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 20

Solute

Answer 20

A substance that is dissolved in a solution.

Question 21

Molecular mass

Answer 21

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

Question 22

Specific heat

Answer 22

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

Question 23

Solvent

Answer 23

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

Question 24

Temperature

Answer 24

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

Question 25

Polar molecule

Answer 25

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

Question 26

Adhesion

Answer 26

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

Question 27

Cohesion

Answer 27

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

Question 28

Kinetic energy

Answer 28

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

Question 29

Heat of vaporization

Answer 29

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

Question 30

Calorie

Answer 30

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

Question 31

Thermal energy

Answer 31

Kinetic energy due to the random motion of atoms and molecules; energy in its most random form; Thermal energy in transfer from one body of matter to another.

Question 32

Ocean acidification

Answer 32

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