Chapter 2: Chemical Basis of Life

Question 1

What are the elements that most living matter is composed of?

Answer 1

oxygen, carbon, hydrogen, nitrogen, calcium, phosphorus

Question 2

Trace elements are common additives to

Answer 2

food and water

Question 3

How can radioactive isotopes harm us and how are they helpful?

Answer 3

Damages molecules, especially DNA

valuable in basic research and medicine

• process of photosynthesis
• Alzheimer’s research

Question 4

How are covalent bonds formed?

Answer 4

through the sharing of electrons

Question 5

What is the difference between polar and nonpolar bonds?

Answer 5

polar bonds- unequal sharing of electrons; one side of molecule is more electronegative

nonpolar bonds- equal sharing of electrons

Question 6

What are ionic bonds?

Answer 6

attractions between ions of opposite charges

Question 7

How do chemical reactions change the composition of matter?

Answer 7

composition is changed as bonds are broken and formed to create reactants and products

Question 8

What is cohesion?

Answer 8

tendency of like molecules to stick together

Question 9

What is surface tension?

Answer 9

measure of the difficulty to break the surface of a liquid

Question 10

How is water the solvent of life?

Answer 10

polar solutes dissolve when water molecules surround them; form aqueous solutions

Question 11

What is an acid?

Answer 11

a compound that releases H+ ions in solution

Question 12

What is a base?

Answer 12

a compound that accepts H+ ions in solution

Question 13

A cells pH is maintained at 7, how does this occur?

Answer 13

by buffers, which minimize changes in pH

Question 14

Radioactive isotopes of an atom often have an increased

a) # of neutrons in the nucleus
b) # of protons in the nucleus
c) # of electrons in the nucleus
d) valence

Answer 14

a) # of neutrons in the nucleus

Question 15

Can large proteins dissolve in water?

Answer 15

Yes as long as the protein has enough polar or ionic residues on their surface

Question 16

A solution at pH 6 contains ______ H+ than the same amount of a solution at pH 8.

a) 20 times more
b) 100 times more
c) 2 times less
d) 100 time less

Answer 16

b) 100 times more

Question 17

Most of the unique properties of water result from the fact that water molecules

a) are the most abundant molecules on Earth’s surface
b) are held together by covalent bonds
c) are constantly in motion
d) are polar and form hydrogen bonds

Answer 17

d) are polar and form hydrogen bonds

Question 18

In chemical terms you would say that Coke-a-cola is an aqueous solution where water is the _____, sugar is a ______, and carbon dioxide makes the solution _____.

a) solvent…solute…basic
b) solute…solvent…basic
c) solvent…solute…acidic
d) solute…solvent…acidic

Answer 18

c) solvent…solute…acidic

Question 19

The atomic number of chlorine is 17. Chlorine combines with hydrogen forming the compound hydrogen chloride. Based on the number of valence electrons in the chlorine atom, predict the molecular formula of the compound.

a) H2Cl
b) HCl2
c) HCl
d) HCl4

Answer 19

c) HCl

Question 20

Why can two hydrogen atoms not satisfy the carbon’s valence in methane (CH4)?

Answer 20

carbon atom has a full valence shell, requiring each of its four unpaired electrons to pair with the electrons of a hydrogen atom

Question 21

Carbon 12: atomic number, mass number, valence

Which of these numbers is most related to the chemical behavior of the atom?

Answer 21

atomic number: 6
mass number: 12.01
valence: 4

the electrons in the valence shell

Question 22

What makes a compound an acid or a base?

Give a strong example of each

Answer 22

Acid- higher concentration of H ions than OH
Base- compound that reduces H ion concentration

Strong Acid: HCl
Strong Base: NaOH

Question 23

Do proteins classify as compounds

Answer 23

Yes, proteins are compounds containing C, H, O, N, S,

Question 24

Farmers spray water on crops to protect from freezing temperatures, how do water’s emergent properties contribute to this?

Answer 24

When water is cooled, hydrogen bonds are formed which releases a significant amount of heat. The heat protects the plant’s cells

Question 25

three characteristics of cohesive behavior…

Answer 25

• strong bonding attraction
• helps transport H2O against gravity in plants
• forms surface tension

Question 26

adhesion is the

Answer 26

attraction between different substances (polar w/ nonpolar molecules and surfaces)

Question 27

What is heat of vaporization?

Answer 27

the heat a liquid must absorb in 1g to be converted into a gas

Question 28

increase vaporization…

Answer 28

retains heat

Question 29

what efficiently maintains homeostasis?

Answer 29

dissolved molecules suspended into H2O

Question 30

what state of matter makes for “slow” molecule reaction?

Answer 30

a solid

Question 31

water’s complexity for supporting life

Answer 31

1. cohesive behavior
2. ability to moderate temp.
3. expansion upon freezing
4. versatility as a solvent

Question 32

What happens when ionic compounds are dissolved by water?

Answer 32

ions are surrounded by hydrogen shells

Question 33

what is pH?

Answer 33

measure of hydrogen ions in solution

Question 34

what is an acid?

Answer 34

any substance that dissociates with water to increase H ions

Question 35

A stronger acid indicates…

Answer 35

a lower pH

Question 36

What is a base?

Answer 36

a substance that combines w/ H dissolved ions

Question 37

a stronger base indicates…

Answer 37

a higher pH

Question 38

what are buffers?

Answer 38

a substance resisting changes in pH