Unit Test 1

Front 1

Water is a polar molecule. This means that _____.

Back 1

the opposite ends of the molecule have opposite electrical charges

Hint 1

In the case of water, the oxygen is slightly negative and the hydrogen atoms are slightly positive.

Front 2

In a group of water molecules, hydrogen bonds form between _____.

Back 2

the oxygen atom in one water molecule and a hydrogen atom in another water molecule

Hint 2

The slightly negatively charged region of an oxygen atom of one water molecule is attracted to the slightly positively charged region of a hydrogen atom of another water molecule.

Front 3

What do cohesion, surface tension, and adhesion have in common with reference to water?

Back 3

All are properties related to hydrogen bonding.

Hint 3

The extraordinary qualities of water are emergent properties resulting from hydrogen bonding.

Front 4

Most of water's unique features (for example, its versatility as a solvent, ability to moderate temperature, and cohesive behavior) result from the fact that _____.

Back 4

oxygen attracts electrons more than hydrogen does

Hint 4

Because oxygen is more electronegative than hydrogen, water molecules are polar and form hydrogen bonds that give water its extraordinary properties.

Front 5

The partial charges on a water molecule occur because of _____.

Back 5

the unequal sharing of electrons between the hydrogen and the oxygen atoms of a water molecule

Hint 5

Because oxygen is more electronegative than hydrogen, electrons of the polar bond spend more time closer to the oxygen atom, resulting in a slight negative charge on the oxygen atom and slight positive charges on the hydrogen atoms.

Front 6

The ability of water molecules to form hydrogen bonds with other water molecules and water's ability to dissolve substances that have charges or partial charges are _____.

Back 6

both caused by water's partial charges

Hint 6

Two molecules of water are held together by a hydrogen bond formed between the slight positive charge of the hydrogen and the slight negative charge of the oxygen. Water is a very versatile solvent, a quality traced to the polarity of the water molecule.

Front 7

The phenomenon responsible for the maintenance of a column of water as it moves upward through a vessel is _____.

Back 7

cohesion

Hint 7

Cohesion is a consequence of hydrogen bonding between water molecules.

Front 8

Adhesion is best described as _____.

Back 8

the clinging of one substance to another substance

Hint 8

Adhesion is the attraction of one substance to another.

Front 9

You can fill a glass of water to just slightly above the rim without it spilling over the glass. What property of water best explains this phenomenon?

Back 9

surface tension

Hint 9

Water has a greater surface tension, a measure of how difficult it is to break the surface of a liquid, than most other liquids.

Front 10

Which action would involve the greatest transfer of heat?

..changing the temperature of 1 g of water from 10°C to 90°C
...cooling 10 g of water from 80°C to 40°C
...evaporating 1 g of water at 25°C
...condensing 5 g of steam to liquid water
...raising the temperature of 10 g of ethyl alcohol by 25°C

Back 10

condensing 5 g of steam to liquid water

Hint 10

This would release about 2,900 calories (580 calories/gram x 5 grams).

Front 11

Which example is not an effect of water's high specific heat?

Back 11

Inland regions generally have milder climates than coastal regions.

Hint 11

Coastal regions generally have milder climates than inland regions because large bodies of water release stored heat as the water cools at night.

Front 12

The amount of heat required to change the temperature of 1 g of any substance by 1°C is defined as _____.

Back 12

the specific heat of that substance

Hint 12

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

Front 13

The reason that coastal climates are more moderate than inland climates is due primarily to water's high _____.

Back 13

specific heat

Hint 13

Because of its high specific heat, water's temperature will change less when it absorbs or loses a given amount of heat. Thus, the oceans can absorb and store a huge amount of heat and release it later when the temperature of the air has dropped.

Front 14

Sweating has a cooling effect because of water's high _____.

Back 14

heat of vaporization

Hint 14

Water's high heat of vaporization results in evaporative cooling because when water evaporates, the surface of the water cools down.

Front 15

Water molecules have _____ than molecules of similar size, such as ammonia and methane.

Back 15

a higher boiling point

Hint 15

More heat is needed to vaporize 1 g of water than most other liquids.

Front 16

Because molecules of water are farther apart in ice than in liquid water, _____.

Back 16

ice floats

Hint 16

Because water molecules in ice are farther apart than in liquid water, ice is less dense, and therefore, it floats.

Front 17

Water is a very versatile solvent because water molecules are_____.

Back 17

polar

Hint 17

Because molecules of polar solvents have a positive and a negative pole, polar solvents are excellent solvents for ions and for other polar materials.

Front 18

Sodium chloride (NaCl) dissolves in water because water molecules _____.

Back 18

are polar

Hint 18

Polar water molecules surround the individual ions, separating the sodium from the chloride and shielding the ions from one another.

Front 19

Nonpolar molecules that cluster away from water molecules are called _____ molecules.

Back 19

hydrophobic

Hint 19

Substances that are non-ionic and nonpolar repel water.

Front 20

Hydrophilic substances, but not hydrophobic substances, _____.

Back 20

have charges and partial charges to which water molecules can adhere

Hint 20

Hydrophilic substances are water loving and have an affinity for water. There is an unequal sharing of electrons resulting in a polar molecule, or there is the gain or loss of an electron(s) resulting in the formation of negatively and positively charged ions.

Front 21

Hydrophobic molecules are _____ water.

Back 21

repelled by

Hint 21

A molecule with all nonpolar bonds would not have an affinity for water and therefore would be hydrophobic.

Front 22

Some substances, such as oil and gasoline, will not dissolve in water because _____.

Back 22

their molecules have no charges or partial charges to which water molecules can adhere

Hint 22

The hydrophobic behavior of oil and gasoline molecules results from a prevalence of nonpolar covalent bonds between carbon and hydrogen.

Front 23

An acid is _____.

Back 23

a compound that donates hydrogen ions to a solution

Hint 23

An acid donates hydrogen ions to a solution.

Front 24

Sucrose has a molecular mass of 342 daltons. To make a 2-molar (2 M) solution of sucrose, _____.

Back 24

stir 342 g of sucrose in water to dissolve the sugar, and then add enough water to bring the total volume of the solution up to 0.5 L

Hint 24

Or you could stir 684 g of sucrose in water to dissolve the sugar, and then add enough water to bring the total volume of the solution up to 1 L.

Front 25

A mole of ethyl alcohol weighs 46 g. How many grams of ethyl alcohol are needed to produce 1 L of a 2-millimolar (2 mM) solution?

Back 25

0.092 g

Hint 25

This would produce a 0.002 M or a 2 mM solution.

Front 26

Adding acid tends to ____ of a solution.

Back 26

increase the hydrogen ion concentration and lower the pH

Hint 26

Because pH is a negative log, its value is inversely proportional to the hydrogen ion concentration.

Front 27

Which of the following dissociations is that of an acid?

Back 27

HF → H+ + F-

Hint 27

Hydrofluoric acid (HF) dissociates into a hydrogen ion and a fluoride ion.

Front 28

A glass of grapefruit juice, at pH 3, contains _____ H+ as a glass of tomato juice, at pH 4.

Back 28

ten times as much

Hint 28

The pH scale is a base-10 logarithmic scale. Each unit represents a tenfold increase or decrease in the hydrogen ion concentration.

Front 29

A solution at pH 6 contains ____ than the same amount of solution at pH 8.

Back 29

100 times more H+

Hint 29

Each pH unit change represents a tenfold difference in the hydrogen ion concentration; thus 10 x 10 = 100

Front 30

Adding a base tends to _____ of a solution

Back 30

lower the hydrogen ion concentration and increase the pH

Hint 30

A substance that reduces the hydrogen ion concentration is a base. Reducing the hydrogen ion concentration increases the pH.

Front 31

When the pH of a solution shifts from 7 to 3, how has the hydrogen ion concentration changed?

Back 31

It has increased by 10,000 times.

Hint 31

Because the pH number is the negative log of the hydrogen ion concentration, a change from a pH of 7 to a pH of 3 increases the hydrogen ion concentration by 10,000 times. (7 - 3 = 4; 104 = 10,000.)

Front 32

Pure water has a pH of 7. Why does uncontaminated rainwater have a pH of 5.6?

Back 32

formation of carbonic acid from carbon dioxide and water

Hint 32

The presence of carbonic acid in rain water causes it to have a lower pH than pure water.

Front 33

A substance that minimizes changes in the concentration of H+ and OH- in a solution is a(n) ______.

Back 33

buffer

Hint 33

Buffers are substances that minimize changes in the concentration of hydrogen ions and hydroxide ions in a solution; therefore, buffers maintain a relatively constant pH.

Front 34

Which of the following statements does not correctly describe a buffer?

A buffer can accept H+ ions when needed.
A buffer can donate H+ ions when needed.
A buffer resists changes in the pH of a solution.
A buffer is only partly dissociated.
None of the above (all the above statements correctly describe a buffer).

Back 34

None of the above (all the above statements correctly describe a buffer).

Hint 34

A buffer works by accepting hydrogen ions from the solution when they are in excess and donating hydrogen ions to the solution when they have been depleted, thereby minimizing changes in the concentration of hydrogen ions and hydroxide ions in a solution. This prevents changes in pH.

Front 35

Which of the following statements is true about acid precipitation?
It harms aquatic life, but has little effect on terrestrial life.
It washes away some minerals that are plant nutrients, while causing some toxic minerals to accumulate.
Automobile use is the leading contributor to acid rain.
Industrial areas are hit hardest by acid rain.
None of the above.

Back 35

It washes away some minerals that are plant nutrients, while causing some toxic minerals to accumulate.

Front 36

Cells are surrounded by water, and cells themselves consist of about 70% to 95% water. As a result _____.
(1) the temperature of living things tends to change relatively slowly
(2) a variety of nutrient molecules are readily available as dissolved solutes
(3)waste products produced by cell metabolism can be easily removed
(4)dissolved substances can be easily transported within a cell or between cells in multicellular organisms
(5) all of the above

Back 36

all of the above

Front 37

The tendency of water molecules to stay close to each other as a result of hydrogen bonding _____.

(1)provides the surface tension that allows leaves to float on water
(2)is called cohesion
(3)keeps water moving through the vessels in a tree trunk
(4)acts to moderate temperature
(5)all of the above

Back 37

all of the above