Question 1

Which property of water allows ice to float on liquid water, and why is this important for aquatic life in cold climates?

Accepted Answer

Water is less dense as a solid than as a liquid because hydrogen bonds keep molecules farther apart in ice, insulating aquatic life below.

Question 2

Which of the following best explains why coastal areas have milder climates than inland areas?

Accepted Answer

Water has a high specific heat, so it absorbs and releases heat slowly, moderating temperature changes.

Question 3

A water strider can walk on the surface of a pond without sinking. Which property of water is primarily responsible for this phenomenon?

Accepted Answer

High surface tension due to cohesion among water molecules.

Question 4

Which of the following best describes the difference between heat and temperature?

Accepted Answer

Heat is the total thermal energy transferred, while temperature is the average kinetic energy of molecules.

Question 5

Which of the following is NOT an emergent property of water resulting from hydrogen bonding?

Accepted Answer

Low viscosity

Question 6

How does the structure of a water molecule contribute to its polarity?

Accepted Answer

The oxygen atom is more electronegative, pulling electrons closer and creating partial charges.

Question 7

Which of the following best describes how water moves from the roots to the leaves of a tree?

Accepted Answer

Cohesion holds water molecules together, and adhesion helps them stick to cell walls, allowing upward movement against gravity.

Question 8

Which of the following equations represents the dissociation of water?

Accepted Answer

$$2\ \mathrm{H_2O} \rightleftharpoons \mathrm{H_3O^+} + \mathrm{OH^-}$$

Question 9

A solution has a pH of 4. What is the concentration of hydrogen ions $$[\mathrm{H^+}] in $$this solution?

Accepted Answer

$$[\mathrm{H^+}] = 10$$^{-4}$$\ \mathrm{M}$$

Question 10

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

Accepted Answer

Oil molecules are hydrophobic due to their nonpolar bonds, which do not interact favorably with water's polarity.

Question 11

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

Buffers minimize changes in pH by reversibly binding hydrogen ions.

Question 12

How does the burning of fossil fuels contribute to ocean acidification?

Accepted Answer

It increases atmospheric $$\mathrm{CO_2$}$$, which dissolves in seawater, forming carbonic acid and lowering ocean pH.

Question 13

Which of the following is the correct way to prepare a 1 M solution of ethyl alcohol ($$\mathrm{C_2H_5OH}$$)?

Accepted Answer

Dissolve 1 mole of ethyl alcohol in enough water to make 1 liter of solution.

Question 14

Why do astrobiologists focus on planets that may have water when searching for extraterrestrial life?

Accepted Answer

Water's unique properties make it an ideal solvent for biochemical reactions necessary for life.

Question 15

Which of the following best describes how sweating helps cool the human body?

Accepted Answer

Evaporation of sweat removes heat as water molecules with the highest kinetic energy leave the skin.

Question 16

Which of the following statements about acids and bases is correct?

Accepted Answer

An acid increases $$[\mathrm{H^+}] in a $$solution, while a base decreases $$[\mathrm{H^+}].$$

Question 17

A solution has a pH of 9. Which of the following best describes this solution?

Accepted Answer

It is basic, with a lower $$[\mathrm{H^+}]$$ than pure water.

Question 18

Which of the following best explains why a paper towel can draw in water when it touches a spill?

Accepted Answer

Adhesion between water molecules and the fibers of the towel pulls water upward.

Question 19

Which of the following best describes the bicarbonate buffer system in blood?

Accepted Answer

$$\mathrm{H_2CO_3} \rightleftharpoons \mathrm{$$HCO_3$$^-} + \mathrm{H^+}$$, which helps resist changes in pH by accepting or donating $$\mathrm{H^+}$$ ions.

Water and Life: Properties, Structure, and Biological Importance

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