Question 1

Which property of water allows ice to float on liquid water, and what is the biological significance of this phenomenon in aquatic ecosystems?

Accepted Answer

Water's lower density as a solid due to hydrogen bonding; it insulates aquatic life by forming a surface layer of ice.

Question 2

A student adds table salt (NaCl) to water and observes it dissolving. Which property of water is responsible for this, and what is the molecular explanation?

Accepted Answer

Water's polarity; it surrounds Na+ and Cl- ions with hydration shells, separating them.

Question 3

Which equation correctly describes the relationship between hydrogen ion concentration and pH in an aqueous solution?

Accepted Answer

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

Question 4

Why do coastal cities like Los Angeles have milder temperatures compared to inland cities like Palm Springs, as shown in the temperature map?

Accepted Answer

The ocean absorbs and releases heat slowly due to water's high specific heat, moderating air temperature.

Question 5

An elephant sprays water on itself to cool down. Which process is responsible for the cooling effect, and how does it work?

Accepted Answer

Evaporative cooling; water molecules with the highest kinetic energy leave as vapor, lowering the temperature of the remaining liquid.

Question 6

Which of the following best explains why water is considered the 'solvent of life'?

Accepted Answer

Water's polarity allows it to dissolve ionic and polar molecules, making it versatile for biological reactions.

Question 7

A solution has a hydrogen ion concentration of $$1 	imes 10$$^{-4}$$ M. What is its pH?

Accepted Answer

$$4$$

Question 8

Which statement correctly describes the function of buffers in biological systems?

Accepted Answer

Buffers maintain pH by neutralizing acids and bases, preventing drastic changes in pH.

Question 9

What is the effect of ocean acidification on marine organisms such as corals, and which chemical reaction is involved?

Accepted Answer

Ocean acidification increases H+ ions, which combine with carbonate ions, reducing the availability of carbonate for calcification ($$\mathrm{CO}_3$$^{2-}$$ + \mathrm{Ca}^{2+} \rightarrow \mathrm{CaCO}_3).$$

Question 10

Which of the following substances is most likely to be hydrophobic?

Accepted Answer

Vegetable oil

Question 11

If a person’s blood pH drops below 7.2, which buffer system responds, and what is the chemical reaction involved?

Accepted Answer

The bicarbonate buffer system; bicarbonate ions ($$\mathrm{HCO}_3^-) $$bind excess H+ to form carbonic acid ($$\mathrm{H}_2\mathrm{CO}_3$$): $$\mathrm{HCO}_3^- + \mathrm{H}^+ \rightarrow \mathrm{H}_2\mathrm{CO}_3.$$

Question 12

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

Accepted Answer

Acids donate H+ ions, lowering pH; bases donate OH- ions, raising pH.

Question 13

A student tests a solution with blue litmus paper, which turns red. What does this indicate about the solution?

Accepted Answer

The solution is acidic.

Question 14

Which of the following scenarios would most likely result in metabolic acidosis in the human body?

Accepted Answer

Uncontrolled diabetes leading to excess production of acidic ketone bodies.

Question 15

Which of the following best explains why water has a high specific heat?

Accepted Answer

Hydrogen bonds between water molecules require significant energy to break, so temperature changes slowly.

Question 16

Which of the following equations represents the constant product of hydrogen and hydroxide ion concentrations in pure water at 25ºC?

Accepted Answer

$$[\mathrm{H}^+][\mathrm{OH}^-] = 10$$^{-14}$$

Question 17

Which of the following is a real-world consequence of the loss of Arctic sea ice, as shown in the ecosystem diagram?

Accepted Answer

Polar bears lose habitat, while some whales and phytoplankton may benefit from increased open water.

Question 18

Which of the following best describes a hydrophilic substance?

Accepted Answer

A substance that has an affinity for water and dissolves easily due to its polar or ionic nature.

Question 19

A protein is placed in water and dissolves. What property of the protein allows this to happen?

Accepted Answer

The protein has ionic and polar regions that interact with water molecules.

Water and Life: Properties, Functions, and Biological Importance

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