Question 1

Which property of water allows insects like water striders to walk on its surface, and what is the molecular basis for this property?

Accepted Answer

Surface tension resulting from hydrogen bonding between water molecules

Question 2

Why is ice less dense than liquid water, and why is this important for aquatic life?

Accepted Answer

Ice forms a crystalline structure stabilized by hydrogen bonds, causing molecules to be spaced further apart. This allows ice to float, insulating aquatic environments and enabling life to survive beneath.

Question 3

A student adds table salt (NaCl) to water and observes it dissolves. Which property of water explains this phenomenon?

Accepted Answer

Water's polarity enables it to surround and separate Na+ and Cl- ions, dissolving the salt.

Question 4

Which equation correctly relates the pH of a solution to its hydrogen ion concentration?

Accepted Answer

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

Question 5

If a solution has a pH of 3 and another has a pH of 6, how many times greater is the hydrogen ion concentration in the pH 3 solution compared to the pH 6 solution?

Accepted Answer

$$10^3$$ times greater

Question 6

Which statement best explains why water has a high specific heat?

Accepted Answer

Hydrogen bonds between water molecules absorb and release heat slowly, stabilizing temperature changes.

Question 7

A protein denatures when the pH of its environment changes from 7 to 3. What is the most accurate explanation for this observation?

Accepted Answer

The increase in hydrogen ion concentration disrupts ionic and hydrogen bonds in the protein, altering its structure.

Question 8

Which of the following best describes a hydrophilic substance?

Accepted Answer

A substance that has an affinity for water due to its polar or charged nature.

Question 9

What is the role of buffers in biological systems?

Accepted Answer

Buffers minimize changes in pH by accepting or donating protons ($$\mathrm{H}^+) as $$needed.

Question 10

Which process describes the transformation of water from liquid to gas, and why is it important for living organisms?

Accepted Answer

Evaporative cooling, which helps regulate temperature in organisms and environments.

Question 11

Ocean acidification is primarily caused by which chemical reaction involving carbon dioxide and water?

Accepted Answer

$$\mathrm{CO}_2 + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{H}_2\mathrm{CO}_3$$

Question 12

Which type of bond is responsible for water's cohesion and surface tension?

Accepted Answer

Hydrogen bonds between water molecules

Question 13

Why does water act as an excellent solvent for many biological molecules?

Accepted Answer

Water's polarity allows it to interact with and dissolve other polar and ionic substances.

Question 14

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

Accepted Answer

Bent, due to the two lone pairs of electrons on the oxygen atom

Question 15

A solution has a pH of 8. What is the concentration of hydrogen ions ($$[\mathrm{H}^+]) in $$this solution?

Accepted Answer

$$1 	imes 10$$^{-8}$$ M

Question 16

Which of the following is a consequence of ocean acidification for marine organisms?

Accepted Answer

Decreased saturation state of calcium carbonate, making it harder for organisms to build shells

Question 17

Which statement correctly describes the relationship between pH and [H$$^+$$] concentration?

Accepted Answer

As pH decreases, [H$$^+$$] concentration increases.

Question 18

Which of the following best explains why water molecules are attracted to each other?

Accepted Answer

Water molecules are polar, allowing hydrogen bonds to form between the partial positive hydrogen and partial negative oxygen atoms.

Question 19

Which property of water helps regulate Earth's climate and temperature in coastal regions?

Accepted Answer

High specific heat, which allows water to absorb and release large amounts of heat with little temperature change

Properties of Water and Their Importance in Biology

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