Chapter 3: water

Question 1

The water molecule is a ___: The opposite ends have opposite charges.

Answer 1

polar molecule

Question 2

Four of water’s properties that facilitate an environment for life are:​

Answer 2

Cohesive behavior​

Ability to moderate temperature​

Expansion upon freezing​

Versatility as a solvent

Question 3

Collectively, hydrogen bonds hold water molecules together, a phenomenon called ___

Answer 3

cohesion​

Cohesion helps the transport of water against gravity in plants

Question 4

___ is an attraction between two different substances, for example, between water and plant cell walls

Answer 4

Adhesion

Question 5

___ is a measure of how hard it is to break the surface of a liquid

Answer 5

Surface tension

Question 6

The ___ of a substance is the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1ºC

Answer 6

specific heat

Question 7

Water’s high specific heat can be traced to ___

Answer 7

hydrogen bonding

Question 8

The ___ of water minimizes temperature fluctuations to within limits that permit life

Answer 8

high specific heat

Question 9

As a liquid evaporates, its remaining surface cools, a process called ___

Answer 9

evaporative cooling ​

Evaporative cooling of water helps stabilize temperatures in individual organisms

Question 10

Ice floats in liquid water because, Solid water, or ice, is less ___ than liquid water. Ice is less dense than water because the orientation of hydrogen bonds causes molecules to push farther apart, which lowers the density.

Answer 10

dense

Question 11

A ___ is a liquid that is a homogeneous mixture of substances

Answer 11

solution

Question 12

A ___ is the dissolving agent of a solution​

Answer 12

solvent

Question 13

The ___ is the substance that is dissolved​

Answer 13

solute

Question 14

In an ___ water is the solvent

Answer 14

aqueous solution

Question 15

A ___ substance is one that has an affinity for water (water-loving)

Answer 15

hydrophilic

Question 16

A ___ substance is one that does not have an affinity for water (water-fearing)

Answer 16

hydrophobic

Oil molecules are hydrophobic

Question 17

A hydrogen atom in a hydrogen bond between two water molecules can shift from one to the other:
The hydrogen atom leaves its electron behind and is transferred as a proton, or hydrogen ion
(The molecule that lost the proton is now a ___

The molecule with the extra proton is now a ___, though it is often represented as H+

Answer 17

hydroxide ion (OH–)

hydronium ion (H3O+)

Question 18

Water is in a state of ___ in which water molecules dissociate at the same rate at which they are being reformed
In pure water, the concentration of the hydronium ion (H3O+ or H+) is equal to the concentration of the hydroxide ion (OH-)

Answer 18

dynamic equilibrium

Question 19

Changes in concentrations of H+ and OH– can drastically affect the ___ of a cell

Answer 19

chemistry

Question 20

Adding certain solutes, called ___ and ___, changes the concentrations of H+ and OH–

Answer 20

acids and bases

Question 21

Biologists use something called the ___ to describe whether a solution is acidic or basic

Answer 21

pH scale

Question 22

The pH scale ranges from ___.

Answer 22

0 to14

Question 23

An ___ is any substance that increases the H+ concentration of a solution

Answer 23

acid

Acidic solutions have pH values less than 7

Question 24

A ___ is any substance that reduces the H+ concentration (or increases the OH- concentration) of a solution

Answer 24

base (alkaline)

A basic solution has a pH value greater than 7

Question 25

Most biological fluids have pH values in the range of ___

Answer 25

6 to 8

Question 26

Each pH unit represents a ___ change in H+ ion concentration.

Answer 26

10 fold magnitude

10x10, 10x10x10, etc

Question 27

___ are substances that minimize changes in concentrations of H+ and OH– , and help maintain the pH of cells at a constant level

Answer 27

Buffers

The internal pH of most living cells must remain close to pH 7