Question 1

Which property of water is primarily responsible for the ability of some insects, such as water striders, to walk on the surface of a pond without sinking?

Accepted Answer

Surface tension due to cohesion

Question 2

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

Accepted Answer

Hydrogen bonds in ice are more ordered, making ice less dense than liquid water, which allows it to float and insulate the water below.

Question 3

A scientist adds a strong acid to a beaker of pure water. What immediate effect does this have on the concentrations of $$[H^+]$$ and $$[OH^-] in $$the solution?

Accepted Answer

$$[H^+]$$ increases and $$[OH^-]$$ decreases

Question 4

Which of the following best explains why water has a high specific heat compared to most other substances?

Accepted Answer

Hydrogen bonds between water molecules require a large amount of energy to break.

Question 5

A solution has a pH of 4. What is the concentration of hydrogen ions $$[H^+] in $$this solution?

Accepted Answer

$$1 	imes 10$$^{-4}$$ M

Question 6

Which of the following scenarios best illustrates the concept of evaporative cooling?

Accepted Answer

Sweat evaporates from human skin, removing heat and cooling the body.

Question 7

If a plant cell is placed in a solution with a high concentration of nonpolar molecules, what is the most likely effect on the cell's water content?

Accepted Answer

Water will not interact with the nonpolar molecules and may remain in the cell.

Question 8

Which of the following best describes the role of buffers in biological systems?

Accepted Answer

Buffers minimize changes in pH by reversibly binding or releasing $$H^+$$ ions.

Question 9

A beaker contains 100 mL of water at 25°C. If you add 100 calories of heat, what will be the final temperature of the water? (Assume no heat loss to the environment. The specific heat of water is $$1 \ \mathrm{cal}/(\mathrm{g} \cdot ^\circ\mathrm{C})$$ and the density of water is $$1 \ \mathrm{g}/\mathrm{mL}.)$$

Accepted Answer

26°C

Question 10

Which of the following statements about water's polarity is correct?

Accepted Answer

Water is polar because oxygen is more electronegative than hydrogen, resulting in an uneven distribution of charge.

Question 11

Which of the following best explains why salt (NaCl) dissolves readily in water?

Accepted Answer

The polarity of water molecules allows them to surround and separate Na$$^+$$ and Cl$$^-$$ ions.

Question 12

A lake remains liquid under a layer of ice during winter. Which property of water is most directly responsible for this phenomenon?

Accepted Answer

Expansion upon freezing, making ice less dense than liquid water

Question 13

Which of the following is a real-world consequence of ocean acidification caused by increased atmospheric CO$$_2$$?

Accepted Answer

Decreased pH of seawater, leading to coral bleaching and harm to marine life

Question 14

Which of the following best describes the difference between hydrophilic and hydrophobic substances?

Accepted Answer

Hydrophilic substances have an affinity for water, while hydrophobic substances do not interact with water due to their nonpolar bonds.

Question 15

A protein dissolves in water because it has regions with which of the following characteristics?

Accepted Answer

Ionic and polar regions that interact with water molecules

Question 16

If the pH of a solution changes from 7 to 5, what happens to the concentration of hydrogen ions $$[H^+]$$?

Accepted Answer

It increases by a factor of 100

Question 17

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

Accepted Answer

Water's polarity allows it to dissolve a wide variety of ionic and polar substances.

Question 18

Which of the following is an example of adhesion?

Accepted Answer

Water molecules forming hydrogen bonds with plant cell walls

Question 19

A student adds 1 g of NaCl to 100 mL of water and stirs until it dissolves. What is the solute in this solution?

Accepted Answer

NaCl

Question 20

Which of the following best describes the process of heat transfer when water cools from 80°C to 20°C?

Accepted Answer

Hydrogen bonds form, releasing heat to the environment.

Water and Life: Properties and Biological Importance of Water

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