Question 1

Which property of water allows a water strider to walk on the surface of a pond without sinking?

Accepted Answer

Surface tension

Question 2

Why is ice less dense than liquid water?

Accepted Answer

Hydrogen bonds in ice form a lattice that spaces molecules farther apart

Question 3

A solution has a hydrogen ion concentration of $$10^{-4} M. $$What is its pH?

Accepted Answer

$$pH = -\log_{10}(10$$^{-4}$$) = 4$$

Question 4

Which of the following best explains why NaCl dissolves readily in water?

Accepted Answer

Water molecules surround and separate Na+ and Cl- ions due to their polarity

Question 5

Which statement best describes an amphipathic molecule?

Accepted Answer

It contains both hydrophilic and hydrophobic regions

Question 6

What is the primary reason water is an excellent solvent for polar molecules?

Accepted Answer

Water molecules can form hydrogen bonds with polar solutes

Question 7

Which property of water is most directly responsible for the upward movement of water in plants?

Accepted Answer

Cohesion and adhesion

Question 8

A buffer is important in biological systems because it:

Accepted Answer

Minimizes changes in pH when acids or bases are added

Question 9

If the pH of a solution changes from 6 to 4, the concentration of H+ ions:

Accepted Answer

Increases by 100-fold

Question 10

Which of the following best describes the relationship between acids, bases, and pH?

Accepted Answer

Acids increase [H+], lowering pH; bases decrease [H+], raising pH

Question 11

Which of the following is a consequence of changes in pH within living cells?

Accepted Answer

Protein shape and function may be altered

Question 12

Which of the following best explains why oil does not dissolve in water?

Accepted Answer

Oil molecules are nonpolar and cannot form hydrogen bonds with water

Question 13

What is the effect of adding a strong acid to pure water?

Accepted Answer

The [H+] increases and the pH decreases

Question 14

Which of the following equations correctly represents the dissociation of water?

Accepted Answer

$$\mathrm{H_2O} \rightleftharpoons \mathrm{OH^-} + \mathrm{H^+}$$

Question 15

A solution with a pH of 2 has how many times more hydrogen ions than a solution with a pH of 5?

Accepted Answer

1000 times more

Question 16

Which property of water is most important for maintaining temperature stability in living organisms?

Accepted Answer

High specific heat

Question 17

Which of the following best describes the role of hydrogen bonds in water's unique properties?

Accepted Answer

They are responsible for water's cohesion, adhesion, and high surface tension

Question 18

Why do living cells require buffers to maintain homeostasis?

Accepted Answer

Buffers minimize changes in pH, protecting cellular processes

Question 19

Which of the following is an example of a hydrophilic substance?

Accepted Answer

Table salt (NaCl)

Question 20

Which of the following best explains why changes in pH can affect enzyme activity?

Accepted Answer

Changes in pH can alter the shape of the enzyme's active site

Properties of Water and Their Biological Significance

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