Question 1

Which property of water is primarily responsible for the ability of some insects, such as water striders, to walk on the surface of ponds?

Accepted Answer

Water's high surface tension due to cohesion

Question 2

Why does ice float on liquid water, and what would be the consequence if it did not?

Accepted Answer

Ice is less dense than liquid water because hydrogen bonds keep water molecules farther apart in ice; if it sank, bodies of water would freeze solid, threatening life.

Question 3

A solution contains 0.01 mol/L of $$H^+$$ ions. What is the pH of this solution?

Accepted Answer

$$pH = 2$$

Question 4

Which of the following best explains why water is an effective solvent for ionic compounds?

Accepted Answer

Water molecules are polar, allowing them to surround and separate ions due to their partial charges.

Question 5

During a hot day, sweating helps cool the human body. Which property of water is most directly responsible for this cooling effect?

Accepted Answer

Evaporative cooling due to high heat of vaporization

Question 6

A buffer solution contains a weak acid and its corresponding base. What is the main function of this buffer in biological systems?

Accepted Answer

To minimize changes in pH when acids or bases are added

Question 7

Which of the following scenarios best illustrates adhesion?

Accepted Answer

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

Question 8

If the concentration of $$OH^-$$ ions in a solution is $$1 	imes 10$$^{-6}$$ mol/L, what is the pOH of the solution?

Accepted Answer

$$pOH = 6$$

Question 9

Which of the following is a direct consequence of water's high specific heat for coastal climates?

Accepted Answer

Coastal climates experience milder temperature fluctuations due to water absorbing and releasing heat slowly.

Question 10

Which of the following best describes a hydrophobic molecule?

Accepted Answer

A molecule that does not have an affinity for water and contains mostly nonpolar bonds

Question 11

A plant is able to transport water from its roots to its leaves against gravity. Which combination of water properties is most responsible for this process?

Accepted Answer

Cohesion and adhesion

Question 12

Which of the following equations correctly represents the dissociation of water into hydronium and hydroxide ions?

Accepted Answer

$$2H_2O \rightarrow H_3O^+ + OH^-$$

Question 13

Which of the following would most likely happen if the pH of human blood dropped by 0.4 units?

Accepted Answer

It could be deadly, as blood pH is tightly regulated.

Question 14

Which property of water allows it to minimize temperature fluctuations and thus support life on Earth?

Accepted Answer

High specific heat

Question 15

Which of the following best explains why water is called the 'universal solvent'?

Accepted Answer

Water's polarity allows it to dissolve many ionic and polar substances.

Question 16

A solution has a pH of 5. How many times more acidic is it than a solution with a pH of 7?

Accepted Answer

100 times

Question 17

Which of the following is true about hydrophilic substances?

Accepted Answer

They have an affinity for water and often contain polar or charged groups.

Question 18

Which of the following best describes the role of buffers in living organisms?

Accepted Answer

Buffers minimize changes in concentrations of $$H^+$$ and $$OH^-$$ ions.

Question 19

Which of the following is a direct result of water's ability to form hydrogen bonds?

Accepted Answer

Water has high surface tension and cohesive behavior.

Question 20

If a lake absorbs a large amount of heat from the sun but its temperature rises only slightly, which property of water is being demonstrated?

Accepted Answer

Water's high specific heat

Water: The Elixir of Life – Properties and Biological Importance

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