Question 1

Which property of water allows a raft spider to walk on its surface, as shown in the image, and what molecular interaction is responsible for this property?

Accepted Answer

Surface tension; hydrogen bonds between water molecules

Question 2

Why does ice float on liquid water, and what is the structural difference between ice and liquid water at the molecular level?

Accepted Answer

Ice floats because it is less dense than liquid water; in ice, hydrogen bonds are more ordered and stable.

Question 3

A tree transports water from its roots to its leaves. Which two properties of water are most directly involved in this process, and how do they work together?

Accepted Answer

Cohesion and adhesion; cohesion holds water molecules together, and adhesion helps water stick to cell walls.

Question 4

Which equation correctly represents the dissociation of water molecules into ions?

Accepted Answer

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

Question 5

A solution has a pH of 5. Which statement best describes its properties?

Accepted Answer

It is acidic, with $$[\mathrm{H}^+] \u003e [\mathrm{OH}^-]$$

Question 6

Which property of water is responsible for the moderation of coastal temperatures, as shown in the temperature map of Southern California?

Accepted Answer

High specific heat

Question 7

What is the main reason water is considered a versatile solvent?

Accepted Answer

Its polarity, which allows it to form hydration shells around ions and dissolve polar molecules

Question 8

If you dissolve 58.44 g of NaCl (molecular mass = 58.44 g/mol) in enough water to make 1 liter of solution, what is the molarity (M) of the solution?

Accepted Answer

$$1\ \mathrm{M}$$

Question 9

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 with water's polarity.

Question 10

What is the effect of ocean acidification on marine organisms that build shells from calcium carbonate?

Accepted Answer

It decreases the availability of carbonate ions, making shell formation more difficult.

Question 11

Which equation describes the relationship between pH and hydrogen ion concentration?

Accepted Answer

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

Question 12

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

Accepted Answer

To minimize changes in $$[\mathrm{H}^+]$$ and $$[\mathrm{OH}^-]$$ concentrations

Question 13

Which of the following statements about water’s high specific heat is correct?

Accepted Answer

Water’s high specific heat is due to hydrogen bonding, which absorbs heat when bonds break and releases heat when bonds form.

Question 14

Which scenario best illustrates evaporative cooling in a biological context?

Accepted Answer

Sweating in humans, where evaporation of water from the skin cools the body

Question 15

If the concentration of $$[\mathrm{H}^+] in a $$solution is $$1 	imes 10$$^{-4}$$ M, what is the pH of the solution?

Accepted Answer

$$4$$

Question 16

Which of the following is a real-world consequence of the loss of Arctic sea ice due to global warming?

Accepted Answer

Decreased survival for species like polar bears and walruses that depend on ice

Question 17

Which of the following best describes the relationship between hydrophilic and hydrophobic substances and their interaction with water?

Accepted Answer

Hydrophilic substances have an affinity for water due to their polar or ionic nature, while hydrophobic substances do not interact with water due to their nonpolar nature.

Question 18

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

Accepted Answer

Low specific heat

Question 19

Which process is responsible for the formation of hydration shells around ions when salt is dissolved in water?

Accepted Answer

Polarity of water molecules attracting and surrounding ions

Water and Life: Properties, Structure, and Biological Importance

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