Question 1

Which property of water allows insects such as water striders to walk on its surface without sinking?

Accepted Answer

High surface tension due to hydrogen bonding

Question 2

Water has a high specific heat. What is the biological significance of this property for living organisms?

Accepted Answer

It helps organisms maintain stable internal temperatures despite fluctuations in environmental temperature.

Question 3

Which of the following best explains why ice floats on liquid water?

Accepted Answer

Hydrogen bonds in ice create a relatively open crystal structure, making it less dense than liquid water.

Question 4

A solution has a hydrogen ion concentration of $$1 	imes 10$$^{-4}$$ mol/L. What is its pH?

Accepted Answer

$$4$$

Question 5

Which of the following statements about water’s polarity is correct?

Accepted Answer

Water is polar because oxygen has a partial negative charge and hydrogen has a partial positive charge.

Question 6

Sweating cools the body primarily because of which property of water?

Accepted Answer

Water’s high heat of vaporization

Question 7

Which of the following best describes a buffer in biological systems?

Accepted Answer

A substance that resists changes in pH by accepting or donating hydrogen ions.

Question 8

Why is water considered a versatile solvent in biological systems?

Accepted Answer

Its polarity allows it to dissolve both ionic and polar substances.

Question 9

Which equation correctly represents the relationship between pH and hydrogen ion concentration $$[H^+]$$?

Accepted Answer

$$\mathrm{pH} = -\log_{10}[H^+]$$

Question 10

A lake is covered by a layer of ice in winter. Which property of water is most directly responsible for the survival of aquatic life beneath the ice?

Accepted Answer

Water’s expansion upon freezing, making ice less dense than liquid water

Question 11

Which of the following is a direct consequence of water’s ability to form hydrogen bonds?

Accepted Answer

Water has a high boiling point compared to similar-sized molecules.

Question 12

A scientist adds a strong acid to a solution, causing the pH to drop from 7 to 3. By what factor did the hydrogen ion concentration increase?

Accepted Answer

$$10^4$$

Question 13

Which of the following best describes the process of evaporative cooling?

Accepted Answer

The surface of a liquid cools down as the molecules with the highest kinetic energy leave as gas.

Question 14

Which of the following is NOT a property of water that contributes to the sustainability of life on Earth?

Accepted Answer

Low surface tension

Question 15

Which statement best explains why salt (NaCl) dissolves easily in water?

Accepted Answer

Water’s polarity allows it to surround and separate Na+ and Cl- ions.

Question 16

If a solution has a pH of 9, what is its hydrogen ion concentration $$[H^+]$$?

Accepted Answer

$$1 	imes 10$$^{-9}$$ mol/L

Question 17

Which of the following scenarios best illustrates the concept of adhesion?

Accepted Answer

Water molecules sticking to the walls of plant vessels, helping transport water upward.

Question 18

Which property of water is most important for the transport of nutrients and waste in the bloodstream?

Accepted Answer

Versatility as a solvent

Question 19

Which of the following best describes the molecular structure of water?

Accepted Answer

Bent molecule with polar covalent bonds

Question 20

A solution contains a buffer. What will happen if a small amount of acid is added?

Accepted Answer

The buffer will accept excess hydrogen ions, minimizing the change in pH.

Water and Life: Properties, Structure, and Biological Importance

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