Question 1

Which property of water is primarily responsible for its ability to moderate Earth's climate and maintain stable temperatures in large bodies of water?

Accepted Answer

Its high specific heat capacity, $$1 \mathrm{cal}/(\mathrm{g} \cdot ^\circ \mathrm{C})$$

Question 2

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

Accepted Answer

Ice floats because its hydrogen bonds are more ordered, making it less dense than water; if it sank, bodies of water would freeze solid, making life impossible.

Question 3

A student spills vinegar (acetic acid, pH ≈ 3) on a table. Which statement best describes the change in hydrogen ion concentration compared to pure water ($$\mathrm{pH} = 7$$)?

Accepted Answer

The hydrogen ion concentration is 1,000 times higher in vinegar than in pure water.

Question 4

Which of the following best explains why water is an excellent solvent for ionic and polar substances?

Accepted Answer

Water molecules are polar, allowing them to form hydration shells around ions and polar molecules.

Question 5

Which process is responsible for the cooling effect when sweat evaporates from human skin?

Accepted Answer

Evaporative cooling, where water molecules with the highest kinetic energy leave the surface

Question 6

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

Accepted Answer

Buffers minimize changes in concentrations of H$$^+$$ and OH$$^-$$ ions, helping maintain a stable pH.

Question 7

A plant transports water from its roots to its leaves against gravity. Which two properties of water are most directly involved in this process?

Accepted Answer

Cohesion and adhesion

Question 8

Which statement correctly describes the relationship between hydrogen bonding and the high specific heat of water?

Accepted Answer

Hydrogen bonds must break to increase water's temperature, requiring more energy and resulting in a high specific heat.

Question 9

Which of the following best describes a hydrophobic molecule?

Accepted Answer

A molecule with relatively nonpolar bonds that does not have an affinity for water

Question 10

If the pH of a solution changes from 8 to 6, what happens to the hydrogen ion concentration?

Accepted Answer

It increases by a factor of 100

Question 11

Which of the following is an example of water's surface tension in nature?

Accepted Answer

A gecko walking across a pond without sinking

Question 12

Which equation correctly represents the dissociation of water molecules?

Accepted Answer

$$2\mathrm{H}_2\mathrm{O} \rightleftharpoons \mathrm{H}_3\mathrm{O}^+ + \mathrm{OH}^-$$

Question 13

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

Accepted Answer

Its high specific heat, which helps regulate internal temperature

Question 14

A solution has a pH of 5. Which of the following statements is true?

Accepted Answer

It is acidic and has more H$$^+$$ ions than OH$$^-$$ ions.

Question 15

Which of the following best explains why water expands upon freezing?

Accepted Answer

Hydrogen bonds in ice are more ordered, causing molecules to be spaced further apart.

Question 16

Which of the following is NOT an emergent property of water that contributes to Earth's suitability for life?

Accepted Answer

High compressibility

Question 17

A protein dissolves in water because it contains regions with which type of chemical bonds?

Accepted Answer

Ionic and polar bonds

Question 18

Which statement best describes the difference between cohesion and adhesion in water?

Accepted Answer

Cohesion is the attraction between water molecules; adhesion is the attraction between water and other substances.

Question 19

Which of the following would most likely disrupt homeostasis in a cell?

Accepted Answer

A sudden change in pH outside the range of 6-8

Question 20

Which of the following best describes the effect of adding a base to an aqueous solution?

Accepted Answer

It decreases the concentration of H$$^+$$ ions.

Water and Life: Properties and Biological Importance of H₂O

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