biology chapter 3

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Many mammals control their body temperature by sweating. Which property of water is most directly responsible for the ability of sweat to lower body temperature?

the absorption of heat by the breaking of hydrogen bonds

A slice of pizza has 500 kcal. If we could burn the pizza and use all the heat to warm a 50-L container of cold water, what would be the approximate increase in the temperature of the water? (Note: A liter of cold water weighs about 1 kg.)

10°C

The bonds that are broken when water vaporizes are

hydrogen bonds between water molecules.

Which of the following is a hydrophobic material?

wax

We can be sure that a mole of table sugar and a mole of vitamin C are equal in their

number of molecules

How many grams of acetic acid (C2H4O2) would you use to make 10 L of a 0.1 M aqueous solution of acetic acid? (Note: The atomic masses, in daltons, are approximately 12 for carbon, 1 for hydrogen, and 16 for oxygen.)

60.0 g

Measurements show that the pH of a particular lake is 4.0. What is the hydrogen ion concentration of the lake?

10-4 M

What is the hydroxide ion concentration of the lake described in question 7?

10-10 M

Cells are surrounded by water, and cells themselves consist of about 70% to 95% water. As a result _____.

all of the above

Water is a polar molecule. This means that _____.

the opposite ends of the molecule have opposite electrical charges

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

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

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

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

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

all of the above

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

All are properties related to hydrogen bonding

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 _____.

oxygen attracts electrons more than hydrogen does

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 _____.

both caused by water's partial charges

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

cohesion

Adhesion is best described as _____.

the clinging of one substance to another substance

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?

surface tension

Imagine that organisms consisted of 70-95% alcohol instead of 70-95% water. Alcohol's specific heat is about half that of water. How would living things be different?

Systems for temperature regulation would have to be much more efficient

Which action would involve the greatest transfer of heat?

condensing 5 g of steam to liquid water

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

the specific heat of that substance

The amount of heat required to convert 1 g of any substance from the liquid to the gaseous state is defined as _____.

the heat of vaporization of that substance

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

specific heat

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

heat of vaporization

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

a higher boiling point

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

ice floats

Water is a very versatile solvent because water molecules are_____.

polar

How does the polarity of water contribute to its ability to dissolve so many substances?

Because it is polar, water's oppositely charge ends are attracted to positively and negatively charged ions and molecules. Water molecules form a hydration shell around oppositely charged particles.

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

hydrophobic

A molecule that has all nonpolar covalent bonds would be _____.

hydrophobic

Hydrophobic molecules are _____ water.

repelled by

Why are cell membranes composed primarily of hydrophobic molecules?

In order to perform their function of separating the aqueous solutions outside of cells from the aqueous solutions inside of cells, cell membranes cannot be soluble in water.

Hydrophilic substances, but not hydrophobic substances, _____.

have charges and partial charges to which water molecules can adhere

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

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

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

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

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?

0.092 g

An acid is _____.

a compound that donates hydrogen ions to a solution

Adding acid tends to ____ of a solution.

increase the hydrogen ion concentration and lower the pH

Which of the following dissociations is that of an acid?

HF → H+ + F-

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

ten times as much

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

100 times more H+

Adding a base tends to _____ of a solution.

lower the hydrogen ion concentration and increase the pH

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

It has increased by 10,000 times.

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

formation of carbonic acid from carbon dioxide and water

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

buffer

Why is the increasing amount of carbon dioxide being taken up by the oceans a cause for concern?

More carbon dioxide causes an increase in carbonic acid (H2CO3) which leads to a decrease in the concentration of carbonate ion (CO32-).

Which of the following statements is true about acid precipitation?

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

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