2 Chapter Atoms, Molecules, and Life
1) A substance with specific properties that cannot be broken down or converted into another substance is called
a(n):
A) element.
B) molecule.
C) ion.
D) compound.
E) mixture.
2) If you examined the human body, which of the following combinations of elements would be most common?
A) C, O, P, S
B) C, Na, O, N
C) Cl, Ca, C, H
D) C, S, Ca, N
E) O, N, H, C
3) The atomic number of an atom is defined as the:
A) number of electrons in the outermost energy level.
B) total number of energy shells.
C) arrangement of neutrons in the atomic nucleus.
D) number of protons in the atomic nucleus.
E) total number of electrons and neutrons.
4) Phosphorus has an atomic number of 15, so what is the distribution of its electrons?
A) The first energy level has eight and the second has seven.
B) The first energy level has two, the second has eight, and the third has five.
C) The first energy level has two and the second has 13.
D) The first, second, and third energy levels have five electrons each.
E) The electron arrangement cannot be determined from the atomic number alone.
5) Which four elements make up approximately 96% of living matter?
A) carbon, hydrogen, nitrogen, oxygen
B) carbon, sulfur, phosphorus, hydrogen
C) carbon, sodium, chlorine, magnesium
D) carbon, oxygen, sulfur, calcium
E) oxygen, hydrogen, calcium, sodium
6) Imagine that you have been hired as a chemist and your first task is to examine a newly discovered atom. The
paperwork you are given states that its atomic number is 110. What does this mean?
A) The atom contains 110 protons.
B) The atom contains 55 electrons.
C) The atom contains 55 protons and 55 neutrons.
D) The atom is an isotope.
7) Iron is an important element in human body cells. If iron has an atomic number of 26, what does this tell you
about this element?
A) An iron atom has 13 electrons and 13 protons.
B) An iron atom has 13 protons and 13 neutrons.
C) An iron atom has 26 protons.
D) An iron atom is unable to become an isotope.
8) Carbon-14 is often used for carbon dating, where scientists measure the rate of carbon-14 decay to determine the
age of items. Carbon-14 contains six protons and eight neutrons. During the process of carbon-14 decay, one of its
eight neutrons becomes a proton and an electron is emitted. Which of the following is the BEST explanation of what
has occurred?
A) The resulting atom still has an unstable nucleus.
B) The resulting atom is now a different element because the number of protons has changed.
C) The resulting atom is still carbon-14.
D) An ionic bond has formed.
9) Radioactive isotopes are biological tools that are often used to: A) measure the size of fossils.
B) detect brain tumors.
C) build up a store of calcium in a cell.
D) increase the pH of blood.
10) For an atom to achieve maximum stability and become chemically inert, what must occur?
A) Its outermost energy shell must be filled with electrons.
B) The number of electrons must equal the number of protons.
C) Electron pairs are shared.
D) Ionization occurs.
11) An atom's nucleus is composed of:
A) protons only.
B) neutrons only.
C) protons and electrons.
D) protons and neutrons.
E) neutrons and electrons.
12) The formation of ions involves the:
A) sharing of electrons.
B) gain or loss of electrons.
C) gain or loss of protons.
D) sharing of protons.
E) gain or loss of neutrons.
13) If a certain atom has a tendency to lose two electrons, this lends itself to the formation of a(n):
A) polar molecule.
B) ion.
C) water molecule.
D) isotope.
14) The formation of sodium chloride (NaCl) is the result of:
A) covalent bonding.
B) chemical unreactivity.
C) attraction between opposite charges.
D) the lack of chemical attraction.
15) Atoms or molecules that have gained or lost electrons are called: A) acids.
B) bases.
C) polymers.
D) ions.
E) buffers.
16) Most biological molecules are joined by:
A) peptide bonds.
B) ionic bonds.
C) hydrogen bonds.
D) disulfide bonds.
E) covalent bonds.
17) Sulfur is an essential element in the human body, and studying its characteristics is important in understanding
human physiology. Sulfur atoms have six electrons in their outer shell. Based on this information, which of the
following is true?
A) Sulfur can form important molecules using covalent bonds.
B) Sulfur is inert.
C) Sulfur is an important isotope of hydrogen.
D) Sulfur has eight electrons in its outer shell.
18) Which of the following could potentially be a free radical?
A) oxygen (atomic number 8)
B) helium (atomic number 2)
C) neon (atomic number 10)
19) Free radicals are considered dangerous because they:
A) attack the atomic nucleus.
B) emit dangerous radiation.
C) steal electrons from other atoms, causing them to become free radicals.
D) damage oxygen and cause it to become an antioxidant.
20) Scientists recommend a diet rich in antioxidants to stay healthy. What occurs at the atomic level to explain this
recommendation?
A) Antioxidants stop the chain reaction of cellular damage caused by free radicals.
B) Antioxidants cause an increase in pH, which is necessary for neutrality in cells.
C) Antioxidants steal electrons, which gives cells extra energy.
D) Antioxidants are inert and do not interact with free radicals.
21) Which of the following BEST explains why a particular atom may not form compounds readily?
A) The atom has no electrons.
B) The atom has an uneven number of protons.
C) The atom has seven electrons in its outer shell.
D) The atom's outer energy shells are completely full.
22) The element carbon has atomic number 6. Carbon most likely:
A) forms an ionic bond.
B) forms four covalent bonds.
C) forms two covalent bonds.
D) donates two electrons to another atom.
23) Sodium (Na), atomic number 11, has a tendency to lose an electron in the presence of chlorine. After losing the
electron, Na has ________ protons in its nucleus.
A) 10
B) 11
C) 12
D) 21
E) 22
24) Carbon has atomic number 6. Carbon most likely:
A) shares electrons.
B) gains electrons.
C) loses electrons.
D) shares protons.
E) loses protons.
25) What does H?O?H represent?
A) an atom of water
B) a mixture including water
C) a molecule of water
D) ionic bonding of water
26) The atomic number of hydrogen is 1. Based on this fact, all of the following must be true of hydrogen gas (H2)
EXCEPT that it:
A) is stable.
B) is covalently bonded.
C) shares one pair of electrons.
D) is polar.
27) Polar covalent bonds form when:
A) electrons are shared unequally between atoms.
B) more than one pair of electrons is shared.
C) ions are formed.
D) an acid and a base are combined.
E) atoms from two molecules are attracted to each other.
28) Which of the following represents a molecule characterized by polar covalent bonding?
A) NaCl
B) H2
C) H2O
D) C?C
E) CH4
29) What type of bond is easily disrupted in aqueous solutions?
A) covalent
B) polar covalent
C) ionic
30) If sulfur has an atomic number of 16, how many covalent bonds does it form?
A) 0
B) 2
C) 4
D) 6
E) 8
31) The part of the atom that has the greatest biological interest and influence is the:
A) proton.
B) electron.
C) neutron.
D) innermost electron shell.
32) Which of the following pairs has the most similar chemical properties?
A) 1H and 22Na
B) 12C and 28Si
C) 16O and 32S
D) 12C and 14C
E) 1H and 2He
33) A single covalent chemical bond represents the sharing of how many electrons?
A) 1
B) 2
C) 3
D) 4
E) 6
34) Polar molecules:
A) have an overall negative electric charge.
B) have an equal distribution of electric charge.
C) have an overall positive electric charge.
D) have an unequal distribution of electric charge.
E) are always ions.
35) The hydrogen bond between two water molecules forms because water is:
A) polar.
B) nonpolar.
C) a liquid.
D) a small molecule.
E) hydrophobic.
36) Which of the following often form(s) as a result of polar bonds? A) ionic bonds
B) hydrogen bonds
C) peptide ice
E) bonds
D) water
37) Which statement is an accurate description of water molecules?
A) They are ionically bonded.
B) They are charged and nonpolar.
C) They are slightly charged and polar.
D) They are uncharged and nonpolar.
38) Which of the following is an example of hydrogen bonding?
A) the bond between O and H in a single molecule of water
B) the bond between O of one water molecule and H of a second water molecule
C) the bond between O of one water molecule and O of a second water molecule
D) the bond between H of one water molecule and H of a second water molecule
E) the bond between the H of a water molecule and H of a hydrogen molecule
39) Which of the following results from a transfer of electron(s) between atoms?
A) nonpolar covalent bond
B) polar covalent bond
C) ionic bond
D) hydrogen bond
E) electron?proton interaction
40) Which of the following results from an unequal sharing of electrons between atoms?
A) nonpolar covalent bond
B) polar covalent bond
C) ionic bond
D) hydrogen bond
E) electronproton interaction
41) Which of the following best explains the attraction of water molecules to each other?
A) nonpolar covalent bond
B) polar covalent bond
C) ionic bond
D) hydrogen bond
E) electronproton interaction
42) Which of the following is least affected by the presence of water? A) nonpolar covalent bond
B) polar covalent bond
C) ionic bond
D) hydrogen bond
E) electronproton interaction
43) What happens when hydrochloric acid (HCl) is added to pure water? A) The HCl molecules separate into H+
and Cl- ions.
B) The water has a decrease of H+ ions.
C) The HCl molecules float on top of the water.
D) The concentration of OH- ions increases.
E) The pH of the solution increases.
44) An atom of nitrogen attracts electrons more strongly than an atom of hydrogen. Which of the following BEST
describes ammonia (NH3)?
A) The nitrogen is more slightly positive.
B) The nitrogen is strongly negative.
C) The hydrogens are more slightly positive.
D) The hydrogens are strongly negative.
E) Charges balance out and none of the atoms has any charge.
45) If a substance measures 7 on the pH scale, that substance:
A) has equal concentrations of H+ and OH- ions.
B) may be lemon juice.
C) has a higher concentration of OH- than H+ ions.
D) probably lacks OH- ions.
E) is basic.
46) A neutral solution:
A) has no H+.
B) has no OH- .
C) has equal amounts of H+ and OH- .
D) is hydrophobic.
E) has a pH of 0.
47) How do buffers work?
A) They soak up extra acid and base.
B) They accept or release H+.
C) They accept or release OH- .
D) They convert H+ and OH- to water.
E) They monitor the blood pH.
48) The human body must maintain a constant pH. In the blood, bicarbonate serves as a(n) ________ to help
maintain the necessary pH. A) acid
B) buffer
C) base
D) solvent
49) Milk of magnesia is often used to treat stomach upset. It has a pH of 10. Based on this information, milk of
magnesia:
A) is a base.
B) is hydrophobic.
C) is an acid.
D) has the same pH as stomach acid.
50) What is meant by the statement that water has a high specific heat?
A) It can absorb a lot of energy without changing temperature.
B) It grows hot very quickly.
C) The boiling point of water is very low.
D) Water can heat up to only a certain temperature.
E) Water freezes easily.
51) Which property (or properties) of water enables it to function as a moderator of temperature for living
organisms?
A) high specific heat
B) high heat of vaporization
C) high heat of fusion
D) high specific heat and high heat of vaporization
E) high specific heat, high heat of vaporization, and high heat of fusion
52) The fact that salt dissolves in water is BEST explained by the:
A) slightly charged nature of water molecules.
B) polar nature of water molecules.
C) hydrophobic nature of salt.
D) ionic nature of water molecules.
E) hydrophobic nature of the water.
53) Hydrophilic molecules:
A) form hydrogen bonds among themselves.
B) are neutral and nonpolar.
C) readily dissolve in water.
D) do not readily dissolve in water.
E) are repelled by water.
54) Water moves through a plant because of the property of:
A) high heat of fusion.
B) high heat of vaporization.
C) high specific heat.
D) cohesion.
55) Water molecules are cohesive because they:
A) create surface tension.
B) form hydrogen bonds.
C) contain protons.
D) stick to other polar molecules.
E) are repelled by nonpolar molecules.
56) When the acidic level of human blood increases, how is homeostasis maintained?
A) Bicarbonate (HCO3-) releases H+ ions that combine with excess OH- ions to form H2O.
B) H+ ion-donor levels increase.
C) Bicarbonate (HCO3-) accepts H+ ions and forms carbonic acid.
D) Carbonic acid eats up the extra OH- ions.
57) As ice melts, it:
A) absorbs heat from its surroundings.
B) becomes less dense.
C) increases its property of cohesion.
D) increases its heat of vaporization.
58) What determines the cohesiveness of water molecules?
A) hydrogen bonds
B) ionic bonds
C) covalent bonds
D) hydrophobic interactions
59) If you place a paper towel in a dish of water, the water will:
A) separate into H+ and OH- ions, which will react with the paper towel molecules.
B) dissolve the towel because water is a good solvent.
C) move away from the towel because water molecules have hydrophobic interactions.
D) move up the towel as the water adheres to the paper towel while the cohesive water molecules stay bound to each
other.
E) move up the towel because water molecules move quickly as it vaporizes.
60) Sweating is a useful cooling mechanism for humans because water: A) takes up a great deal of heat in changing
from its liquid state to its gaseous state.
B) takes up a great deal of heat in changing from its solid state to its liquid state.
C) can exist in two states at temperatures common on Earth.
D) is an outstanding solvent.
E) ionizes readily.
61) In general, a substance that carries an electric charge can dissolve in water. Given this fact, which of the
following would most likely NOT dissolve in water?
A) ionic compounds
B) polar covalent molecules
C) nonpolar molecules
D) NaCl
62) If you place a feather on the surface of a bowl of water, the feather remains suspended on the surface due to the:
A) surface tension of the water.
B) fact that water is a good solvent.
C) polarity of the water.
D) density of the water.
63) The specific heat of water is 10 times greater than that of iron. You place a metal pot full of water on the stove to
heat it up. You touch the metal handle of the pot when the water is still only lukewarm. Which of the following
BEST describes what happens?
A) You find that the handle is cooler than the water in the pot.
B) You burn your finger and pull your hand away from the very hot handle.
C) You find that both the water and the handle are the same temperature.
D) You determine that metal pots full of water produce acids and bases.
64) You drop a handful of salt into a glass of water. Which of the following BEST describes what is happening
inside the glass at the molecular level?
A) The positively charged hydrogen ends of the water molecules are attracted to sodium ions.
B) The positively charged hydrogen ends of the water molecules are attracted to chloride ions.
C) Sodium and chloride ions form a covalent bond.
D) Water and sodium form a covalent bond.
65) Your friend does a belly flop into the pool. The stinging pain he feels is most likely due to the:
A) surface tension of water.
B) fact that water is a good solvent.
C) pH of the water.
D) hydrophobic nature of your friend's skin.
66) Which of the following is the most dense?
A) liquid water
B) water vapor
C) ice
67) Unlike a rock, a reptile can sit in the hot sunshine without its body temperature soaring quickly. This is because
the water in its body:
A) has a high specific heat.
B) has a low specific heat.
C) is a good solvent.
D) is a poor solvent.