Question 1

Which property of water allows certain insects to walk on its surface without sinking, and what is the molecular basis for this property?

Accepted Answer

Surface tension, resulting from hydrogen bonds between water molecules

Question 2

Why does ice float on liquid water, and what is the biological significance of this phenomenon?

Accepted Answer

Ice is less dense than liquid water because hydrogen bonds form a more ordered structure, insulating aquatic life below

Question 3

A solution has a hydrogen ion concentration of $$1 	imes 10$$^{-5}$$ M. What is its pH?

Accepted Answer

$$5$$

Question 4

Which of the following best explains why water is called the 'universal solvent'?

Accepted Answer

Water's polarity allows it to form hydrogen bonds with many substances, dissolving both ionic and polar molecules

Question 5

Which of the following scenarios demonstrates the importance of water's high specific heat in a real-world context?

Accepted Answer

Coastal cities experience milder temperatures compared to inland cities due to the ocean's ability to absorb and release heat slowly

Question 6

A buffer solution is added to a beaker of water. Which of the following best describes the function of the buffer?

Accepted Answer

It minimizes changes in pH by accepting or donating hydrogen ions ($$H^+) as $$needed

Question 7

Which of the following best describes the difference between acids and bases?

Accepted Answer

Acids increase the concentration of $$H^+$$ ions in solution, while bases decrease it by accepting $$H^+ or $$releasing $$OH^-$$ ions

Question 8

If the pH of rainwater drops from 5.6 to 4.6, how much more acidic has the rainwater become?

Accepted Answer

10 times more acidic

Question 9

Which of the following is a direct consequence of acid precipitation on terrestrial ecosystems?

Accepted Answer

Leaching of essential nutrients like calcium and magnesium from the soil, harming plant growth

Question 10

Which of the following best explains why water can moderate temperature within living organisms and environments?

Accepted Answer

Water has a high specific heat, so it absorbs or releases large amounts of heat with only slight changes in its own temperature

Question 11

A marine biologist observes that coral reefs are declining in areas with increased atmospheric $$CO_2. $$Which chemical process is most directly responsible for this decline?

Accepted Answer

$$CO_2$$ reacts with water to form carbonic acid, which lowers ocean pH and reduces the availability of carbonate ions needed for coral skeletons

Question 12

Which of the following best describes the molecular structure of water that leads to hydrogen bonding?

Accepted Answer

Water has polar covalent bonds, resulting in partial positive charges on hydrogen atoms and a partial negative charge on oxygen

Question 13

Which of the following is an example of water's adhesive property in a biological context?

Accepted Answer

Water molecules sticking to the walls of plant vessels, aiding in the transport of water from roots to leaves

Question 14

A scientist adds a nonpolar substance to water and observes that it does not dissolve. Which property of water explains this observation?

Accepted Answer

Water is polar and forms hydrogen bonds with other polar or ionic substances, but not with nonpolar substances

Question 15

Which equation correctly represents the dissociation of water?

Accepted Answer

$$H_2O \rightleftharpoons H^+ + OH^-$$

Question 16

Which of the following best describes the role of buffers in maintaining blood pH?

Accepted Answer

Buffers, such as the bicarbonate system, absorb excess $$H^+ or$$ $$OH^- to $$keep blood pH close to 7.4

Question 17

Which of the following is a consequence of acid rain on aquatic ecosystems?

Accepted Answer

Increased solubility of toxic aluminum compounds, which can poison fish

Question 18

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

Accepted Answer

Evaporation of water from the skin absorbs heat as hydrogen bonds are broken

Question 19

A solution has a pH of 3. How many times more acidic is it than a solution with a pH of 6?

Accepted Answer

1000 times more acidic

Question 20

Which of the following is a real-world example of water's cohesive property?

Accepted Answer

Water droplets forming beads on a car windshield after rain

Water and Life: Properties, Structure, and Biological Importance

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