A6 fiffAnswers
A1: When you shake the bottle, the olive oil will form small
beads of oil. As the bottle rests, these beads of oil will float back
to the top of the bottle and coalesce into a layer of oil; that is, the
bottle will return to its starting condition. Shaking the bottle will
distribute the vinegar molecules through the water, and they will
remain in solution.
Q2: What would happen if you added another fat to the bottle,
such as bacon grease, and shook it?
A2: Bacon grease is a fat and, like the olive oil, would form small
beads of fat that would float back to the top of the bottle and
coalesce into a layer of grease.
Q3: Given how sugar behaves when it is mixed into coffee or tea,
would you predict that it is hydrophobic or hydrophilic?
A3: Sugar dissolves in coffee and tea; therefore, it is hydrophilic.
Figure 3.6
Q1: Identify where in the picture water can be seen in its liquid,
solid, and gas states.
A1: The water in the hot springs is in a liquid state. The snow and
ice are solid water. Water vapor (steam) in the air is a gas.
Q2: In the gas state, water molecules move too rapidly and are too
far apart to form hydrogen bonds. Compare the volumes occupied
by an equal number of water molecules in the liquid, solid, and gas
states.
A2: The same number of molecules will occupy more volume in
both ice (solid) and water vapor (gas) than in liquid water. The
volume of ice is defined (9% greater than the volume in water)
because the water molecules form an ordered array. The volume of
water vapor depends on its temperature.
Q3: Explain in your own words how ice floats on water.
A3: Water molecules are farther apart in ice than they are in liquid
water. Because the same number of water molecules occupies a
greater volume in ice than in water, the density of ice is lower than
that of water, and ice floats.
Figure 3.7
Q1: Suppose you were going to repeat Miller’s experiments. How
would you decide how much of each gas to include in the chamber?
A1: Miller wanted to replicate the atmosphere of early Earth, so he
based his mixtures on estimates of the proportions of the gases in
the atmosphere at that time.
Q2: Why did the addition of steam to the gases in Miller’s second
set of experiments increase the yield of amino acids?
A2: The steam (hot water vapor) added heat energy to the mixture,
and the water enabled more kinds of chemical reactions.
Q3: Miller used electrical energy in his experiment. What other
forms of energy were present in the early atmosphere of Earth that
could have led to the formation of complex molecules?
A3: Heat and ultraviolet light were present in early Earth’s
atmosphere.
Figure 3.8
Q1: How did the NASA scientists find the fragments of the
meteorite that exploded over eastern Africa?A1: The fragments from the asteroid were dark and stood out
against the light-colored sand in Sudan.Q2: What piece of evidence suggests that amino acids found in the
meteorite fragments originated in outer space?A2: Some of the amino acids from the meteorite fragments have a
“right-handed” orientation, whereas all naturally occurring amino
acids on Earth are in a “left-handed” orientation.Q3: Speculate on the significance of finding extraterrestrial amino
acids.A3: The existence of extraterrestrial amino acids suggests that at
least some of the building blocks of life are found in outer space.Figure 3.9
Q1: Which has a higher concentration of free hydrogen ions:
vinegar, pH 2.8; or milk, pH 6.5?A1: A high concentration of free hydrogen ions corresponds to a
low pH. Thus, vinegar has a higher concentration of free hydrogen
ions than milk has.Q2: What happens to the concentration of free hydrogen ions in
your stomach when you drink a glass of milk?A2: The concentration of free hydrogen ions decreases (that is, the
pH increases).Q3: Black coffee has a pH of 5. Does adding coffee to water (pH 7)
increase or decrease the concentration of free hydrogen ions in the
liquid?A3: The concentration of free hydrogen ions increases.Figure 3.10
Q1: In methane gas, how many electrons is each hydrogen atom
sharing? How many is the carbon atom sharing?A1: Each hydrogen is sharing one electron with carbon. Carbon is
sharing four electrons.Q2: In carbon dioxide, how many electrons is each oxygen atom
sharing? How many is the carbon atom sharing?A2: Each oxygen is sharing two electrons with carbon. Carbon is
sharing four electrons.Q3: Draw a molecule of formaldehyde (CH 2 O). How many
electrons is the oxygen atom sharing with the carbon atom? How
many is the carbon atom sharing with the oxygen atom and with
each hydrogen atom?