U1 Chapter 2: The Chemical Context of Life

Question 1

Matter

Answer 1

Anything that takes up space and has mass

Question 2

Element

Answer 2

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

Question 3

Compound

Answer 3

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

Question 4

Essential Elements

Answer 4

An organism needs to live a healthy life and reproduce

Question 5

Trace Elements

Answer 5

Required by an organism in only minute quantities, some trace elements such as iron (Fe) are needed by all forms of life; others are required only by certain species

Question 6

Atom

Answer 6

The smallest unit of matter that still retains the properties of an element

Question 7

Half-Life

Answer 7

The time it takes for 50% of the parent isotope to decay

Question 8

Radiometric Dating

Answer 8

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

Question 9

Energy

Answer 9

The capacity to cause change, ex. by doing work
- potential energy, is the energy that matter possesses because of its location or structure

Question 10

Covalent Bond

Answer 10

The sharing of a pair of valence electrons by two atoms

Question 11

Single Bond

Answer 11

A pair of shared electrons

Question 12

Electronegativity

Answer 12

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

Question 13

Nonpolar Covalent Bond

Answer 13

The electrons are shared equally because the two atoms have the same electronegativity–the tug of war is at a standoff
- polar covalent bonds are where the electrons are not equally shared

Question 14

Cation

Answer 14

A positively charged ion

Question 15

Anion

Answer 15

Negatively charged ion

Question 16

Ionic Bond

Answer 16

Cation and Anion attraction

Question 17

Hydrogen Bond

Answer 17

Noncovalent attraction between a hydrogen and an electronegative atom

Question 18

Van Der Waals Interactions

Answer 18

Individually weak and occur only when atoms and molecules are very close together and when such interactions occur simultaneously, it can be powerful like a gecko climbing a wall

Question 19

Chemical Equilibrium

Answer 19

The point at which the reactions offset one another
- this is a dynamic equilibrium where reactions are still going on in both directions, but with no net effect on the concentrations of reactants and products