Chapter 2: Chemical Context of Life

Question 1

Matter

Answer 1

anything that takes up space and has mass (i.e. rocks, metals and gases)

Question 2

Element

Answer 2

a substance that cannot be broken down to other substances by chemical reactions

Question 3

Compound

Answer 3

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

Question 4

Essential Elements

Answer 4

elements that an organism needs to live a healthy life and reproduce (i.e. oxygen, carbon and hydrogen)

Question 5

Trace Elements

Answer 5

elements that an organism in only minute quantities

Question 6

Neutrons

Answer 6

subatomic particles with a neutral charge located in nucleus

Question 7

Protons

Answer 7

subatomic particles with a positive charge located in nucleus

Question 8

Electrons

Answer 8

subatomic particles with a negative charge located outside of nucleus

Question 9

Atomic Nucleus

Answer 9

protons and neutrons are packed together tightly in a dense core at center of atom (protons give nucleus a positive charge)

Question 10

Dalton

Answer 10

a unit of measurement for atoms and subatomic particles

Question 11

Atomic Number

Answer 11

number of protons in atom

Question 12

Mass Number

Answer 12

total number of neutrons and protons in nucleus of an atom

Question 13

Atomic Mass

Answer 13

total mass of an atom — neutrons and protons have close mass to 1 dalton (electrons mass is negligible)

Question 14

Isotope

Answer 14

different atomic forms of the same element

Question 15

Radioactive Isotope

Answer 15

the nucleus decays spontaneously, giving off particles and energy — when decay leads to change in number of protons, it transforms the atom to an atom of a different element (i.e. carbon -14 loses a proton becoming an atom of nitrogen)

Question 16

Radioactive Tracers

Answer 16

radioactive isotopes are incorporated into biologically active molecules, which are then used as tracers to track atoms during metabolism (chemical processes of an organism)

Question 17

Half-Life

Answer 17

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

Question 18

Radiometric Dating

Answer 18

scientists measure the ratio of different isotopes and calculate how may half-lives (years) have passed since an organism was fossilized or a rock was formed

Question 19

Energy

Answer 19

capacity to cause change by doing work

Question 20

Potential Energy

Answer 20

energy that matter possesses because of its location or structure (remember: electrons of an atom have potential energy due to their distance from nucleus)

Question 21

Electron Shell

Answer 21

An energy level of electrons at a characteristic average distance from the nucleus of an atom (remember: electron can only at certain energy levels, not between them)

Question 22

Valence Electrons

Answer 22

outer electrons

Question 23

Valence Shell

Answer 23

outermost electron shell

Question 24

Orbital

Answer 24

three-dimensional space where an electron is found 90% of the time

Question 25

Chemical Bonds (strong bond)

Answer 25

atoms with incomplete valence shells can interact with certain other atoms in such a way that each partner atom completes its valence shell: the atoms either share or transfer valence electrons…interactions result in atoms staying close together…the attraction is a…

Question 26

Covalent Bond

Answer 26

sharing of a pair of valence electrons

Question 27

Single Bond

Answer 27

a pair of shared electrons

Question 28

Double Bond

Answer 28

two pairs of shared electrons

Question 29

Valence

Answer 29

atom’s bonding capacity and usually equals the number of unpaired electrons required to complete the atom’s outermost (valence) shell

Question 30

Electronegativity

Answer 30

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

Question 31

Nonpolar Covalent Bond

Answer 31

in a covalent bond, the electrons are equally shared because the two atoms have the same electronegativity

Question 32

Polar Covalent Bond

Answer 32

when an atom is bonded to a more electronegative atom, the electrons are not shared equally

Question 33

Ions

Answer 33

two atoms are so unequal in their attraction for valence electrons that the more electronegative atom strips an electron away from the partner, the two resulting oppositely charge atoms (or molecules) are…

Question 34

Cation

Answer 34

positively charged ion

Question 35

Anion

Answer 35

negatively charged ion

Question 36

Ionic Bond

Answer 36

because of their opposite charges, cations and anions attract each other; this attraction is an…

Question 37

Ionic Compounds (salts)

Answer 37

compounds formed by ionic bonds (remember: ionic compound does not consist molecules…NaCl indicates only the ratio of elements in a crystal of the salt)

Question 38

Hydrogen Bond

Answer 38

this attraction between a hydrogen and an electronegative atom

Question 39

Van der Waals Interaction

Answer 39

Electrons are not always evenly distributed; at any instant, they may accumulate by chance in one part of a molecule or another. The results are ever-changing regions of positive and negative charge that enable all atoms and molecule to stick to one another. (Remember: individually weak and occur only when atoms and molecules are very close together)

Question 40

Chemical Reaction

Answer 40

the making and breaking of chemical bonds, leading to changes in the composition of matter (all atoms of reactants must be accounted for in products/only rearrange, not destroy atoms)

Question 41

Reactants

Answer 41

starting materials of a chemical reaction

Question 42

Products

Answer 42

the resulting materials of a chemical reaction

Question 43

Rate of Reaction

Answer 43

the greater the concentration of reactant molecules, the more frequently they collide with one another and have an opportunity to react and form products

Question 44

Chemical Equilibrium

Answer 44

the forward and reverse reactions occur at the same rate, and the relative concentrations of products and reactants stop changing (the point at which reactions offset each other is…)