Chapter 3

Question 1

Water is the only common substance on Earth to … Furthermore, the solid form of water …

Answer 1

exist in the natural environment in
all three physical states of matter.

floats on the
liquid form, a rare property emerging from the chemistry of the water molecule.

Question 2

. In the Arctic, warmer waters and the smaller ice pack are resulting
in blooms of

Answer 2

phytoplankton (microscopic aquatic photosynthetic organisms), seen
from space as the “cloudy” seawater in

Question 3

. Organisms that depend on Arctic

ice, however, are suffering. For instance,

Answer 3

a population of black guillemots in Alaska is

declining due to the warming climate and reduction of Arctic sea ice.

Question 4

what ability of water makes it cool

Answer 4

the structure of a water molecule allows it to

interact with other molecules, including other water molecules n hydrgrogen bonding ofcccc

Question 5

polar covalent bonds and polarity of water

Answer 5

; these are polar covalent bonds (see Figure 2.11).
This unequal sharing of electrons and water’s V-like shape
make it a polar molecule, meaning that its overall charge
is unevenly distributed. In water, the oxygen of the molecule
has two regions of partial negative charge (δ-), and each
hydrogen has a partial positive charge (δ+).

Question 6

where do the properties of water come from in terms of attractions

Answer 6

The properties of water arise from attractions between oppositely charged atoms of different water molecules: The partially
positive hydrogen of one molecule is attracted to the partially
negative oxygen of a nearby molecule. The two molecules are
thus held together by a hydrogen bond

Question 7

what happens with hydrogen bonds in water

Answer 7

When
water is in its liquid form, its hydrogen bonds are very fragile,
each only about 1/20 as strong as a covalent bond. The hydrogen bonds form, break, and re-form with great frequency. Each
lasts only a few trillionths of a second, but the molecules are
constantly forming new hydrogen bonds with a succession of
partners. Therefore, at any instant, most of the water molecules are hydrogen-bonded to their neighbors

Question 8

the properties of water emerge from

Answer 8

s. The extraordinary
properties of water emerge from this hydrogen bonding, which
organizes water molecules into a higher level of structural order.

Question 9

cohesion

Answer 9

. Collectively, the hydrogen bonds hold

the substance together, a phenomenon called cohesion.

Question 10

importance of cohesion

Answer 10

Cohesion due to hydrogen bonding contributes to the
transport of water and dissolved nutrients against gravity in
plants. Water from the roots reaches the leaves through a network of water-conducting cells (Figure 3.3). As water evaporates from a leaf, hydrogen bonds cause water molecules
leaving the veins to tug on molecules farther down, and the
upward pull is transmitted through the water-conducting
cells all the way to the roots

Question 11

adhesion and importance

Answer 11

Adhesion, the clinging of one
substance to another, also plays a role. Adhesion of water by
hydrogen bonds to the molecules of cell walls helps counter
the downward pull of gravity

Question 12

suface tension d and what is it related t

Answer 12

Related to cohesion is surface tension, a measure of how

difficult it is to stretch or break the surface of a liquid.

Question 13

arangement of water and air at the surface of a liquid and its significance

Answer 13

At the
interface between water and air is an ordered arrangement of
water molecules, hydrogen-bonded to one another and to the
water below, but not to the air above. This asymmetry gives water an unusually high surface tension, making it behave as
though it were coated with an invisible film. You can observe
the surface tension of water by slightly overfilling a drinking glass; the water will stand above the rim

Question 14

how do hydrogen bonds relate to surface tension

Answer 14

. The high surface tension
of water, resulting from the
collective strength of its hydrogen
bonds

Question 15

kinetic energy

Answer 15

Anything that moves has kinetic energy, the energy of
motion. Atoms and molecules have kinetic energy because
they are always moving, although not necessarily in any particular direction

Question 16

thermal energy

Answer 16

The faster a molecule moves, the greater its
kinetic energy. The kinetic energy associated with the random
movement of atoms or molecules is called thermal energy.

Question 17

temp v thermal energy

Answer 17

. Temperature represents the average kinetic energy
of the molecules in a body of matter, regardless of volume,
whereas the thermal energy of a body of matter reflects the
total kinetic energy, and thus depends on the matter’s volume.

Question 18

swimming pool and coffee pot- which has more temp n which has more thermal en

Answer 18

e. Note, however, that although
the pot of coffee has a much higher temperature than, say, the
water in a swimming pool, the swimming pool contains more
thermal energy because of its much greater volume.
Whenever two objects of different temperature are b

Question 19

how does ice cool a drink

Answer 19

Molecules in
the cooler object speed up at the expense of the thermal energy
of the warmer object. An ice cube cools a drink not by adding
coldness to the liquid, but by absorbing thermal energy from
the liquid as the ice itself melts

Question 20

heat

Answer 20

Thermal energy in transfer

from one body of matter to another is defined as heat

Question 21

calorie

Answer 21

One convenient unit of heat used in this book is the calorie
(cal). A calorie is the amount of heat it takes to raise the temperature of 1 g of water by 1°C. Conversely, a calorie is also the
amount of heat that 1 g of water releases when it cools by 1°C.

Question 22

kilocal

Answer 22

A kilocalorie (kcal), 1,000 cal, is the quantity of heat required
to raise the temperature of 1 kilogram (kg) of water by 1°C

Question 23

specific heat

Answer 23

. The specific heat of a substance
is defined as the amount of heat that must be absorbed or lost
for 1 g of that substance to change its temperature by 1°C.

Question 24

water and temperature change

Answer 24

Water resists changing its temperature; when it does change
its temperature, it absorbs or loses a relatively large quantity
of heat for each degree of change.

Question 25

We can trace water’s high specific heat, like many of
its other properties, to 1. Heat must be
2. in order to break hydrogen bonds; by the same
token, heat is 3. when hydrogen bonds form

Answer 25

1. hydrogen bonding
2. absorbed
3. released

Question 26

what happens when water temp decreases only by a lil

Answer 26

And when the temperature of water drops slightly, many
additional hydrogen bonds form, releasing a considerable
amount of energy in the form of heat.

Question 27

why does a calorie of heat cause a small change in temp

Answer 27

much of the heat is used to disrupt hydrogen

bonds before the water molecules can begin moving faster.

Question 28

what is the relevance of waters high spec heat to life?

Answer 28

• large water body can store lots of heat while not warming much.
• at night and in winter the slowly cooling water warms air.
• stabilizes ocean temps-good for fishies
• organisms made of water so they can resist bodily temp changes better than if they had a lower specific heat

Question 29

what hapens if a liquid is heated

Answer 29

the average kinetic energy of

molecules increases and the liquid evaporates more rapidly.

Question 30

heat of vap

Answer 30

Heat of vaporization is the quantity of heat a liquid
must absorb for 1 g of it to be converted from the liquid to the
gaseous state

Question 31

a. Water’s high heat of vaporization
is another 1. resulting from the strength of its
2. which must be 3. before the 4.
can exit from the liquid in the form of 5.

Answer 31

1- emergent propertu
2-h bonds
3-broken
4-molecules
5-water vape

Question 32

evaporative cooling- why and d

Answer 32

As a liquid evaporates, the surface of the liquid that
remains behind cools down (its temperature decreases).
This evaporative cooling occurs because the “hottest”
molecules, those with the greatest kinetic energy, are the
most likely to leave as gas.

Question 33

Evaporative cooling of water contributes to the …and also provides a …

Answer 33

stability of
temperature in lakes and ponds

mechanism that prevents terrestrial organisms from overheating

Question 34

why does water expand upon freezing when other things dont

Answer 34

h bonding

Question 35

when are h bonds btwn mols disrupted

Answer 35

When ice absorbs enough heat

for its temperature to rise above 0°C

Question 36

what happens when water reaches its greatest density at 4 degrees cel

Answer 36

n begins to
expand as the molecules move faster. Even
in liquid water, many of the molecules are
connected by hydrogen bonds, though
only transiently: The hydrogen bonds are
constantly breaking and re-forming.

Question 37

why is water a versatile solvent

Answer 37

its polarity

Question 38

water and salt interface

Answer 38

At the surface of each crystal of salt, the sodium and chloride ions are
exposed to the solvent. These ions and regions of the water
molecules are attracted to each other due to their opposite
charges

Question 39

attraction btwn water n salt

Answer 39

. The oxygens of the water molecules have regions of
partial negative charge that are attracted to sodium cations.
The hydrogen regions are partially positively charged and are
attracted to chloride anion

Question 40

what does water do to salt? hint- whats a hydration shell?

Answer 40

As a result, water molecules surround the individual sodium and chloride ions, separating
and shielding them from one another. The sphere of water
molecules around each dissolved ion is called a hydration
shell

Question 41

what is the result of salt dissovling in water

Answer 41

Working inward from the surface of each salt crystal,
water eventually dissolves all the ions. The result is a solution of two solutes, sodium cations and chloride anions,
homogeneously mixed with water, the solvent.

Question 42

can nonionic polar compounds dissolve in water

Answer 42

yes like sugar

Question 43

how many daltons in a gram and why

Answer 43

Because of the way in
which Avogadro’s number and the unit dalton were originally
defined, there are 6.02 * 10^23 daltons in 1 g.

Question 44

The practical advantage of measuring a quantity of chemicals in moles is that …

Answer 44

a mole of one substance has exactly the

same number of molecules as a mole of any other substance.

Question 45

Measuring in moles
makes it convenient for scientists working in the laboratory
to combine …

Answer 45

substances in fixed ratios of molecules.

Question 46

Molarity—.

Answer 46

the number of moles of solute per liter
of solution—is the unit of concentration most often used by
biologists for aqueous solutions

Question 47

hydroxide ion

Answer 47

The water molecule that lost a proton is now a hydroxide
ion (OH-
), which has a charge of 1-.

Question 48

hydronium ion

Answer 48

-. The proton binds to the
other water molecule, making that molecule a hydronium
ion

Question 49

what is the reversible dissociation rxn of water?

Answer 49

2 H20 –>–< h3o+ + oh-

Question 50

does h+ exist independently in an aqueous solution

Answer 50

t H+
does not exist on its own
in an aqueous solution. It is always associated with a water
molecule in the form of H3O+

Question 51

what happens at the equilibrium pt w the water rxn

Answer 51

At this equilibrium point,
the concentration of water molecules greatly exceeds the
concentrations of H+
and

Question 52

what is the concentration of h n oh in pure water

Answer 52

the
concentration of H+
 and of OH-
 in pure water is therefore
10-7 M (at 25°C

Question 53

e. H+
 and OH-
 are very 1 Changes in their
concentrations can 2. As we have seen, the concentrations of H+
 and OH-
 are equal in pure water, but adding
certain kinds of solutes, 3

Answer 53

reactive 1

2drastically affect a cell’s proteins and
other complex molecules

3called acids and bases, disrupts
this balance

Question 54

acid

Answer 54

An acid is a
substance that increases the hydrogen ion concentration of a
solution. For example, when hydrochloric acid (HCl) is added
to water, hydrogen ions dissociate from chloride ions: (equation on pg 99)This source of H+
(dissociation of water is the other source)
results in an acidic solution—one having more H+
than OH-
.

Question 55

base

Answer 55

A substance that reduces the hydrogen ion concentration
of a solution is called a base. Some bases reduce the H+
concentration directly by accepting hydrogen ions

Question 56

Notice that single arrows were used in the reactions for

HCl and NaOH. why?

Answer 56

These compounds dissociate completely
when mixed with water, so hydrochloric acid is called a
strong acid and sodium hydroxide a strong base

Question 57

ammonia is a weak base. describe its arrows

Answer 57

. In contrast,
ammonia is a weak base. The double arrows in the reaction
for ammonia indicate that the binding and release of hydrogen ions are reversible reactions, although at equilibrium
there will be a fixed ratio of NH4
+
to NH3.

Question 58

what is a weak acid

Answer 58

Weak acids are acids that reversibly release and accept back

hydrogen ions

Question 59

which direction is favored in the dissociation of carbonic acid

Answer 59

Here the equilibrium so favors the reaction in the left direction
that when carbonic acid is added to pure water, only 1% of the
molecules are dissociated at any particular time. Still, that is
enough to shift the balance of H+
and OH-
from neutrality.

Question 60

what happens when a base is added

Answer 60

er. A base has the opposite effect, increasing
OH-
concentration but also reducing H+
concentration by
the formation of water. If enough of a base is added to raise
the OH-
concentration to 10-4 M, it will cause the H+
concentration to drop to 10-10 M

Question 61

what happens when an acid is added

Answer 61

An acid not only adds
hydrogen ions to a solution, but also removes hydroxide
ions because of the tendency for H+
 to combine with OH-
,
forming water

Question 62

. Whenever we know the concentration of either H+
or OH-
in an aqueous solution, what can we do

Answer 62

we can

deduce the concentration of the other ion.

Question 63

pH

Answer 63

The pH of a solution is defined as the negative logarithm
(base 10) of the hydrogen ion concentration:
pH = -log [H+
]
For a neutral aqueous solution, [H+
] is 10-7 M, giving us
-log 10-7 = -(-7) = 7

Question 64

pH ———- as H+ concentratin ________

Answer 64

decreases, increases

Question 65

Notice, too, that although the pH scale is based
on H+
concentration, it also implies …

Answer 65

OH-
concentration.
A solution of pH 10 has a hydrogen ion concentration of
10-10 M and a hydroxide ion concentration of 10-4 M.

Question 66

where do most biological fluids fall in terms of ph

Answer 66

The pH for basic solutions is above 7. Most biological fluids, such as blood and saliva, are within the range of
pH 6–8

Question 67

. When the pH of a solution changes slightly, the actual concentrations of H+
and
OH-
in the solution change

Answer 67

substantially

Question 68

purpose and defintion of buffers

Answer 68

s allows biological
fluids to maintain a relatively constant pH despite the addition of acids or bases. A buffer is a substance that minimizes
changes in the concentrations of H+
 and OH-
 in a solution.

Question 69

explain what happens with the carbonic acid buffer system in the blood. (also know the equation!! pg 101)

Answer 69

a. As mentioned earlier, carbonic acid dissociates
to yield a bicarbonate ion and a h ion. The chemical equilibrium between carbonic acid and bicarbonate acts as a pH regulator, the reaction shifting left or
right as other processes in the solution add or remove hydrogen ions. If the H+
concentration in blood begins to fall (that
is, if pH rises)s. But
when the H+
concentration in blood begins to rise (when
pH drops), the reaction proceeds to the left, with HCO3
-
(the
base) removing the hydrogen ions from the solution and
forming H2CO3. Thus, the carbonic acid–bicarbonate buffering system consists of an acid and a base in equilibrium with
each other.

Question 70

most other buffers are also…

Answer 70

acid base pairs

Question 71

ocean acidification

Answer 71

When CO2 dissolves in seawater, it reacts with water to form
carbonic acid, which lowers ocean pH. This process, known as
ocean acidification, alters the delicate balance of conditions
for life in the oceans

Question 72

explain the process of ocean acidification (on the graph on page 101 and also described further in detail on pg 101)

Answer 72

Some carbon dioxide
(CO2) in the atmosphere dissolves in
the ocean, where it
reacts with water to
form carbonic acid
(H2CO3).
Carbonic acid
dissociates into
hydrogen ions (H+)
and bicarbonate ions
(HCO3
–).
The added H+
combines with
carbonate ions
(CO3
2–), forming
more HCO3
–.
Less CO3
2– is available for calcification
—the formation of
calcium carbonate
(CaCO3)—by marine
organisms such as
corals

Question 73

contrast the h bonds in liquid and in solid water

Answer 73

Ice:
Hydrogen bonds
are stable

Liquid water:
Hydrogen bonds
break and re-form