Ap Biology Chapter 2

Front 1

element

Back 1

substance that cannot be broken down

Front 2

compound

Back 2

substance consisting of two or more elements combined in a fixed ratio

Front 3

atom

Back 3

smallest unit of matter that retains the properties of an element

Front 4

nucleus

Back 4

atom's central core, containing protons and neutrons

Front 5

proton

Back 5

subatomic particle with a single positive electrical charge

Front 6

neutron

Back 6

subatomic particle with no electrical charge

Front 7

electron

Back 7

subatomic particle with a single negative electrical charge, one or more move around the nucleus

Front 8

atomic number

Back 8

number of protons in the nucleus, unique for each element and designated by a subscript

Front 9

isotope

Back 9

form of an element that has the same number of protons but a different number of neutrons, thus differing in atomic mass

Front 10

electron shell

Back 10

energy level of electrons at a characteristic average distance from the nucleus

Front 11

valence shell

Back 11

outermost energy shell of an atom, containing valence electrons

Front 12

chemical bond

Back 12

an attraction between two atoms that results in the obtaining of complete valence shells

Front 13

covalent bond

Back 13

strong chemical bond in which two atoms share one or more pairs of valence electrons

Front 14

single bond

Back 14

a single covalent bond; the sharing of a pair of valence electrons by two atoms

Front 15

double bond

Back 15

a double covalent bond; the sharing of two pairs of valence electrons by two atoms

Front 16

molecule

Back 16

two or more atoms held together by covalent bonds

Front 17

electronegativity

Back 17

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

Front 18

polar covalent bond

Back 18

covalent bond between atoms that differ in electronegativity

Front 19

ion

Back 19

an atom or group of atoms that has gained or lost one or more electrons, thus acquiring a charge

Front 20

ionic bond

Back 20

chemical bond resulting from the attraction between oppositely charged ions

Front 21

hydrogen bond

Back 21

type of weak chemical bond formed by the attraction between a positive hydrogen atom and a negative atom

Front 22

van der Waals interactions

Back 22

weak attractions between molecules or parts of molecules that results from transient local partial charges

Front 23

chemical reaction

Back 23

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

Front 24

reactant

Back 24

a starting material in a chemical reaction

Front 25

product

Back 25

a material resulting from a chemical reaction

Front 26

chemical equilibrium

Back 26

the state in which the rate of the forward reaction equals the rate of the reverse reaction

Front 27

cohesion

Back 27

the linking together of like molecules, often by hydrogen bonds

Front 28

surface tension

Back 28

a measure of how difficult it is to stretch or break the surface of a liquid

Front 29

specific heat

Back 29

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

Front 30

evaporative cooling

Back 30

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

Front 31

heat of vaporization

Back 31

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

Front 32

solvent

Back 32

the dissolving agent of a solution

Front 33

solute

Back 33

a substance that is dissolved in a solution

Front 34

solution

Back 34

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

Front 35

hydrophilic

Back 35

having an affinity for water

Front 36

hydrophobic

Back 36

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

Front 37

molarity

Back 37

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

Front 38

mole (mol)

Back 38

the number of grams of a substance that equals its molecular weight in daltons and contains Avogadro's number of molecules

Front 39

molecular mass

Back 39

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

Front 40

pH

Back 40

a measure of hydrogen ion concentration equal to -log [H+] and ranging in value from 0 to 14

Front 41

buffer

Back 41

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