Chapter 2- The Chemical Context of Life

Question 1

half-life

Answer 1

the amount of time it takes for 50% of a sample of a radioactive isotope to decay.

Question 2

van der Waals interactions

Answer 2

Weak attractions between molecules or parts of molecules that result from transient local partial charges.

Question 3

anion

Answer 3

negatively charged ion

Question 4

reactant

Answer 4

the starting material in a chemical reaction

Question 5

chemical reaction

Answer 5

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

Question 6

chemical bond

Answer 6

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 shells.

Question 7

compound

Answer 7

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

Question 8

ionic compound

Answer 8

a compound resulting from the formation of an ionic bond; also called a salt

Question 9

cation

Answer 9

positively charged ion

Question 10

chemical equilibrium

Answer 10

In a chemical reaction, the state in which the rate of the forward reaction equals the rate of the reverse reaction, so that the relative concentrations of the reactants and products do not change with time.

Question 11

radioactive isotope

Answer 11

an isotope that is unstable; the nucleus decays spontaneously, giving off detectable particles and energy.

Question 12

Molar Solutions

Answer 12

1 mol
___________ = 1 MOLAR (M) in concentration
1 liter of water

Question 13

Brownian Motion

Answer 13

Molecules always moving.

Question 14

ice

Answer 14

Stabilizes a lattice (molecules are further apart- ALL the H bonds are created)

Question 15

cohesion

Answer 15

molecules interacting with the same molecules

Question 16

solutes

Answer 16

substance that is dissolved

Question 17

solvent

Answer 17

dissolving agent

Question 18

solution

Answer 18

homogenous liquid mixture

Question 19

hydrophillic

Answer 19

dipole

Question 20

hydrophobic

Answer 20

nonpolar

Question 21

amphiphilic / amphipathic

Answer 21

molecules having polar water-soluble group attached to water-insoluble group

Question 22

transient dipole

Answer 22

stabilized by molecules next to each other

Question 23

hydrophobic effect

Answer 23

non-interaction of H bonds with water and van de Waals-interactions of the hydrophobic substance

Question 24

acid

Answer 24

any substance that when added to water raises the concentration of H+

Question 25

base

Answer 25

any substance that when added to water reduces the concentration of H+, often raising the OH-

Question 26

Strong vs Weak acids/bases

Answer 26

a STRONG acid/base dissociates completely in water

a WEAK acid/base varies in their degree of dissociation

Question 27

buffers

Answer 27

• substances that RESIST a change in pH.
• weak acids and weak bases = buffers
• they maintain a relatively constant pH by absorbing or releasing [H+]

Question 28

uncharged atom

Answer 28

equal number of protons and electrons

Question 29

unreactive / inert

Answer 29

an atom with a complete valence shell

Question 30

the reactivity of an atom arises from

Answer 30

the existance of unpaired electrons in the valence shell.

Question 31

unstable isotopes

Answer 31

• nucleus decays spontaneously
• radioactive
• can be transformed into an atom of another element

Question 32

decay

Answer 32

• losing subatomic particles

- likely to occur when an atom has too many neutrons