Chapter 2: The Chemical Basis of Life

Question 1

acid

Answer 1

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

Question 2

acid precipitation

Answer 2

Rain, snow, or fog with a pH below 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

atom

Answer 5

The small unit of matter that retains the properties of an element.

Question 6

atomic mass

Answer 6

The approximate total mass of an atom; also called atomic weight. Given as a whole number, the atomic mass approximately equals the mass number.

Question 7

atomic number

Answer 7

The number of protons in each atom of a particular element.

Question 8

base

Answer 8

A substance that decreases the hydrogen ion (H) concentration in a solution.

Question 9

buffer

Answer 9

A chemical substance that resists changes in pH by accepting hydrogen ions from or donating hydrogen ions to solutions.

Question 10

chemical bond

Answer 10

An attraction between two atoms resulting from a sharing of outer-shell electrons or the presence of opposite charges on the atoms. The bonded atoms gain complete outer electron shells.

Question 11

chemical reaction

Answer 11

The making and breaking of chemical bonds, leading to changes in the composition of matter.

Question 12

cohesion

Answer 12

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

Question 13

compound

Answer 13

A substance containing two or more elements in a fixed ratio. For example, table salt (NaCl) consists of one atom of the element sodium (Na) for every atom of chlorine (Cl).

Question 14

covalent bond

Answer 14

An attraction between atoms that share one or more pairs of outer-shell electrons; symbolized by a single line between the atoms.

Question 15

electron

Answer 15

A subatomic particle with a single negative electrical charge. One or more electrons move around the nucleus of an atom.

Question 16

electron shell

Answer 16

An energy level representing the distance of an electron from the nucleus of an atom.

Question 17

electronegativity

Answer 17

The attraction of a given atom for the electrons of a covalent bond.

Question 18

element

Answer 18

A substance that cannot be broken down to other substances by chemical means.

Question 19

heat

Answer 19

Thermal energy; the amount of energy associated with the movement of the atoms and molecules in a body of matter. Heat is energy in its most random form.

Question 20

hydrogen bond

Answer 20

A type of weak chemical bond formed when the partially positive hydrogen atom participating in a polar covalent bond in one molecule is attracted to the partially negative atom participating in a polar covalent bond in another molecule (or in another part of the same macromolecule).

Question 21

ion

Answer 21

An atom that has gained or lost one or more electrons, thus acquiring a charge.

Question 22

ionic bond

Answer 22

A chemical bond resulting from the attraction between oppositely charged ions.

Question 23

isotope

Answer 23

A group of two or more atoms held together by covalent bonds.

Question 24

molecule

Answer 24

A group of two or more atoms held together by covalent bonds.

Question 25

neutron

Answer 25

An electrically neutral particle (a particle having no electrical charge), found in the nucleus of an atom.

Question 26

nonpolar covalent bond

Answer 26

A covalent bond in which electrons are shared equally between two atoms of similar electronegativity.

Question 27

nucleus

Answer 27

(plural, nuclei) (1) An atom’s central core, containing protons and neutrons. (2) The genetic control center of a eukaryotic cell.

Question 28

pH scale

Answer 28

A measure of the relative acidity of a solution, ranging in value from 0 (most acidic) to 14 (most basic). The letters pH stand for potential hydrogen and refer to the concentration of hydrogen ions (H).

Question 29

polar covalent bond

Answer 29

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 30

polar molecule

Answer 30

A molecule containing polar covalent bonds.

Question 31

product

Answer 31

An ending material in a chemical reaction.

Question 32

proton

Answer 32

A subatomic particle with a single positive electrical charge, found in the nucleus of an atom.

Question 33

radioactive isotope

Answer 33

An isotope whose nucleus decays spontaneously, giving off particles and energy.

Question 34

reactant

Answer 34

A starting material in a chemical reaction.

Question 35

salt

Answer 35

A compound resulting from the formation of ionic bonds; also called an ionic compound.

Question 36

solute

Answer 36

A substance that is dissolved in a solution.

Question 37

solution

Answer 37

A liquid consisting of a homogeneous mixture of two or more substances, consisting of a dissolving agent, called the solvent, and a substance that is dissolved, called the solute.

Question 38

solvent

Answer 38

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

Question 39

surface tension

Answer 39

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 40

temperature

Answer 40

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

Question 41

trace element

Answer 41

An element that is essential for life but required in extremely minute amounts.