Question 1

Which property of water allows a water strider to walk on the surface of a pond without sinking?

Accepted Answer

Surface tension due to hydrogen bonding

Question 2

Why does ice float on liquid water, and why is this important for aquatic life in winter?

Accepted Answer

Ice is less dense than liquid water due to stable hydrogen bonds forming a crystal lattice, allowing aquatic life to survive below

Question 3

Which of the following best explains why coastal cities like Los Angeles have milder temperatures compared to inland cities like Palm Springs?

Accepted Answer

Water has a high specific heat, absorbing and releasing heat slowly, moderating temperature changes

Question 4

A salt crystal (NaCl) dissolves in water because:

Accepted Answer

Water molecules form hydration shells around Na+ and Cl- ions, separating them

Question 5

Which equation correctly represents the ionization of water?

Accepted Answer

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

Question 6

A solution with a pH of 4 has how many times more hydrogen ions ($$[H^+]) $$than a solution with a pH of 7?

Accepted Answer

1,000 times more

Question 7

Which of the following best describes a buffer’s function in biological systems?

Accepted Answer

Buffers minimize changes in pH by absorbing or releasing $$H^+$$ ions

Question 8

Why do hydrophobic substances, such as oils, separate from water in a mixture?

Accepted Answer

They have nonpolar bonds and cannot form hydrogen bonds with water

Question 9

Which property of water is most directly responsible for the process of transpiration in plants?

Accepted Answer

Cohesion and adhesion due to hydrogen bonding

Question 10

What is the main biological consequence of ocean acidification caused by increased atmospheric $$CO_2$$?

Accepted Answer

Decreased formation of calcium carbonate ($$CaCO_3$$), threatening calcifying species

Question 11

Which of the following statements about hydrogen bonds in water is correct?

Accepted Answer

Hydrogen bonds are weak individually but strong collectively due to their abundance

Question 12

A protein dissolves in water because:

Accepted Answer

It contains polar or charged regions that interact with water molecules

Question 13

Which of the following best explains why sweating cools the human body?

Accepted Answer

Evaporation of sweat absorbs heat energy, lowering body temperature

Question 14

If a solution has equal concentrations of $$[H^+]$$ and $$[OH^-]$$, what is its pH and how is it classified?

Accepted Answer

pH 7, neutral

Question 15

Which of the following is a direct result of water’s high specific heat for living organisms?

Accepted Answer

Organisms are protected from drastic temperature fluctuations

Question 16

Which of the following best describes the orientation of water molecules around a chloride ion ($$Cl^-) in $$solution?

Accepted Answer

The hydrogen atoms (partial positive) of water face the chloride ion

Question 17

A buffer in human blood helps maintain pH by:

Accepted Answer

Releasing $$H^+$$ ions when the blood becomes too basic and absorbing $$H^+$$ ions when it becomes too acidic

Question 18

Which of the following is NOT an emergent property of water that supports life on Earth?

Accepted Answer

Low boiling point

Question 19

Which of the following best explains why oil and vinegar separate when mixed?

Accepted Answer

Oil is hydrophobic and does not interact with polar water molecules in vinegar

Question 20

Which of the following best describes the relationship between pH and hydrogen ion concentration?

Accepted Answer

pH is the negative logarithm of the hydrogen ion concentration: $$pH = -\log_{10}[H^+]$$

Chapter 3: Water and Life – Study Notes for Biology Students

Study Guide - Practice Questions