Water and Life

Question 1

What does polarity do?

Answer 1

Allows water molecules to form hydrogen bonds with each other

Question 2

What is cohesion?

Answer 2

Hydrogen bonds holding water molecules together

Question 3

What does cohesion result in?

Answer 3

High surface tension, a measure of how difficult it is to stretch or break the surface of a liquid

Question 4

What does cohesion contribute to?

Answer 4

The transport of water and dissolved nutrients against gravity in plants

Question 5

What is adhesion?

Answer 5

An attraction between different substances, for example, water and plant cell walls

Question 6

Water absorbs heat from what?

Answer 6

Warmer air

Question 7

Why does water release stored heat?

Answer 7

For cooler air

Question 8

Water can absorb or release a large amount of heat with only what?

Answer 8

A slight change in its own temperature

Question 9

What is a calorie (cal)?

Answer 9

The amount of heat required to raise the temperature of 1 g of water by 1 degree Celcius

Question 10

What is the specific heat of a substance?

Answer 10

The amount of heat that must be absorbed or lost for 1 g of the substance to change its temperature by 1 degree Celcius

Question 11

What is the equation for the specific heat of water?

Answer 11

1 cal/(g x ºC)

Question 12

Why does water resist changing its temperature?

Answer 12

Because of its high specific heat

Question 13

What is evaporation (or vaporization)?

Answer 13

The transformation of a substance from liquid to gas

Question 14

What is heat of vaporization?

Answer 14

The heat a liquid must absorb for 1 g to be converted to gas

Question 15

What is evaporative cooling?

Answer 15

When liquid evaporates and its remaining surface cools

Question 16

What does evaporative cooling help with?

Answer 16

The stabilizing of temperatures in organisms and bodies of water

Question 17

Is water less dense as a solid or as a liquid?

Answer 17

As a solid

Question 18

When are water molecules locked into a crystalline lattice?

Answer 18

at 0 degrees Celcius

Question 19

Hydrogen bonds keep the molecules far enough apart to make the ice what?

Answer 19

Approx. 10% less dense than liquid water

Question 20

When does water reach its greatest density?

Answer 20

at 4 degrees Celcius

Question 21

Why doesn’t ice sink?

Answer 21

Because all bodies of water would eventually freeze solid if it did

Question 22

What is a solution?

Answer 22

A liquid that is a homogeneous mixture

Question 23

What is a solvent?

Answer 23

The dissolving agent of a solution

Question 24

What is a solute?

Answer 24

The substance that is dissolved

Question 25

When an ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules called what?

Answer 25

A hydration shell

Question 26

What can water dissolve?

Answer 26

Compounds made of nonionic polar molecules

Question 27

What is hydrophilic?

Answer 27

Substance with an affinity for water

Question 28

What is hydrophobic?

Answer 28

Substance that does not have an affinity for water

Question 29

What is molecular mass?

Answer 29

The sum of all masses of all atoms in a molecule

Question 30

What are numbers of molecules usually measured in?

Answer 30

moles, where 1 mol = 6.02 x 10^23 molecules

Question 31

How were avogadro’s number defined?

Answer 31

6.02 x 10^23 daltons = 1 g

Question 32

What is molarity?

Answer 32

The number of moles of solute per liter of solution

Question 33

How do you write the pH of a solution?

Answer 33

pH = -log [H+]

Question 34

What are acidic solutions?

Answer 34

pH values less than 7 (Ex. Urine, Battery Acid)

Question 35

What are basic solutions?

Answer 35

pH values greater than 7 (Ex. Seawater, Oven Cleaner)

Question 36

What are buffers?

Answer 36

Substances that minimize changes in concentrations of H+ and OH- in a solution