Biology Chapter 3- Mastering Questions

Which statement must be mentioned in explaining why amphipathic molecules line up at a water surface?

Polar groups attract one another.

Dissolving is best described as ...

a mingling of molecules and/or ions.

Water is a source of ______________ for chemical reactions in cells.

(a) hydrogen atoms

(b) oxygen atoms

Which statement is true of water's tensile strength?

(a) It results from hydrogen bonding.

(b) It helps to pull water through plants.

(c) It involves both cohesion and adhesion.

Water has surface tension because ...

hydrogen bonds between surface water molecules resist being stretched.

Which of the following helps most to explain why water has a high specific heat?

(a) A water molecule can make 4 hydrogen bonds

Which factor is important in making it possible to cool yourself by sweating? Think carefully!

(a) Molecules collide with varied angles and speeds.

(b) Hydrogen bonds are relatively weak.

Though you add heat, the temperature of boiling water remains constant because ...

it takes energy to break hydrogen bonds.

Which statement helps to explain why ice is less dense than liquid water?

(a) Water molecules make hydrogen bonds at definite angles.

(b) Cold molecules move less than warm molecules.

The open spaces in water's crystal structure make it possible for ...

(a) aquatic life to exist at the North Pole.

Why doesn't oil mix with water?

(c) Polar molecules attract one another.

Many of water's emergent properties, such as its cohesion, its high specific heat, and its high heat of vaporization, result from the fact that water molecules _____.

are attracted to each other by partial negative and positive charges on the oxygen and hydrogen atoms, respectively

Because organisms are made primarily of water, they resist rapid temperature changes. This useful quality is based on water's _____.

high specific heat

In a neutral solution the concentration of _____

hydrogen ions is equal to the concentration of hydroxide ions

A pH of 6 is how many times more acidic than a pH of 9?

1000

Select the statement that best describes a buffer.

d)A buffer resists change in pH by accepting hydrogen ions when acids are added to the solution and donating

Which statement is true of pH buffers?

C. they consist of weak acids and weak bases

A buffer consists of undissociated acid (HA) and the ion made by dissociating the acid (A-). How does this system buffer a solution against decreases in pH?

A⁻ reacts with H⁺ to become HA

Buffers work best when ...

about half of the buffer molecules are dissociated

How does the way a buffer stabilizes pH during addition of acid differ from the way the same buffer stabilizes pH during addition of base?

A. it's the same reaction running backward or forward

Which answer helps to explain why all living cells need pH buffers?

D. Amino acid side chains have many carboxyl and amino gorups

To make a buffer, you need to ...

have a weak acid or a weak base half ionized in water

Which property of water allows dogs to cool themselves by panting?

water's high heat of vaporization

Look at the figure showing the pH values of some familiar aqueous solutions. What is the difference between H+ concentration in an acidic solution such as lemon juice (pH 2) and a basic solution such as household bleach (pH 13)?

The H+ concentration of lemon juice is higher than the H+ concentration of household bleach by a factor of 1011 (100 billion).