Chapter 3

Question 1

Water Molecule

Answer 1

Shaped like a V. It’s two hydrogen atoms joined to the oxygen atom by single covalent bonds. Oxygen is more electronegative than hydrogen, so electrons of the covalent bonds spend more time close to oxygen than to hydrogen, making the bonds polar covalent bonds.

Question 2

Polar Molecule

Answer 2

Overall charge of molecule is unevenly distributed.

Question 3

The properties of water arise from…

Answer 3

Attractions between oppositely charged atoms of different water molecules: The slightly positive hydrogen of one molecule is attracted to the slightly negative oxygen of a nearby molecule. The two molecules are thus held together by a hydrogen bond.

Question 4

Four emergent properties of water that contribute to Earth’s sustainability as an environment for life:

Answer 4

Cohesive behavior
Ability to moderate temperature
Expansion upon freezing
Versatility as a solvent

Question 5

Cohesion

Answer 5

The linkage together of like molecules, often by hydrogen bonds.

Question 6

Adhesion

Answer 6

The clinging of one substance to another.

Question 7

Surface tension

Answer 7

A measure of how difficult it is to stretch or break the surface of a liquid.

Question 8

Kinetic Energy

Answer 8

The energy of motion

Question 9

Thermal energy

Answer 9

The kinetic energy associated with the random movement of atoms or molecules.

Question 10

Difference between temperature and thermal energy.

Answer 10

Temperature is a measure of energy that represents the average kinetic energy of the molecules in a body of matter, regardless of volume, whereas the total thermal energy depends in part on the matter’s volume.

Question 11

How do hydrogen bonds react to heat?

Answer 11

Absorbing heat: Breaks hydrogen bonds.
Releasing heat: Forms hydrogen bonds.

Question 12

Acid

Answer 12

A substance that increases the hydrogen ion concentration of a solution.

Question 13

Base

Answer 13

A substance that reduces the hydrogen ion concentration of a solution.

Question 14

pH

Answer 14

Concentration of hydrogen ion (H+)

Question 15

How does water moderate temperature?

Answer 15

By absorbing heat from air that is warmer and releasing the stored heat to air that is cooler.

Question 16

Heat

Answer 16

Thermal energy in transfer from one body of matter to another.

Question 17

A calorie

Answer 17

Is the amount of heat it takes to raise the temperature of 1 g of water by 1•C.

Question 18

Kilocalorie

Answer 18

Is the quantity of heat required to raise the temperature of 1 kg of water by 1•C.

Question 19

Joule (J)

Answer 19

1J = 0.239 calories (cal)

Question 20

One cal = ___ J

Answer 20

4.184

Question 21

Specific heat

Answer 21

The amount of heat that a substance must absorb or lose for 1 g of that substance to change its temperature by 1•C.

Question 22

Why does water have high specific heat?

Answer 22

Heat is first used to disrupt hydrogen bonds instead of getting molecules to move faster.

Question 23

Vaporization/ Evaporation

Answer 23

Occurs when molecules move fast enough to overcome the attraction to other liquid molecules.

Question 24

Heat of vaporization

Answer 24

Is the quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state.

Question 25

Evaporative cooling

Answer 25

Occurs because the “hottest” molecules are the most likely to leave as gas.

Question 26

As a solid, water is ___________ than as a liquid

Answer 26

less dense

Question 27

When water solidifies, it

Answer 27

Expands

Question 28

Why does water expand when below 4•C?

Answer 28

Because of hydrogen bonds. The molecules are moving too slowly to break the hydrogen bonds.

Question 29

Solution

Answer 29

A liquid that is a homogenous mixture of two or more substances.

Question 30

Solvent

Answer 30

The dissolving agent of the solution.

Question 31

Solute

Answer 31

The substance that is dissolved.

Question 32

Hydration shell

Answer 32

The sphere of water molecules around each dissolved ion. For example, sodium chloride.

Question 33

Molecular mass

Answer 33

The sum of the masses of all the atoms in a molecule.

Question 34

1 mole (mol) Avogadro’s number

Answer 34

6.02 X 10^23 daltons = 1 gram

Question 35

Molarity

Answer 35

The number of moles of solute per liter of solution
- Used for aqueous solutions

Question 36

What happens when a hydrogen atom participating in a hydrogen bond between two water molecules shifts from one molecule to another?

Answer 36

-The hydrogen atom leaves its electron and a Hydrogen ion (H+) is transferred.
- The water molecule that lost a proton is now a hydroxide ion (OH-)
- The proton (H+) bonds to another water molecule, making that molecule a hydronium ion (H3O+)

Question 37

Acidic solution

Answer 37

Has more H+ than OH-

Question 38

In a neutral solution at 25•C…
[H+] = ____
[OH-] = _____
______

Answer 38

[H+] = 10^-7 M
[OH-] = 10^-7 M
[H+][OH-] = 10^-14 M

Question 39

pH formula

Answer 39

pH = -log [H+]

Question 40

For a neutral aqueous solution, [H+] is 10^-7 M, giving us a pH of…

Answer 40

-log 10^-7 = -(-7) = 7

Question 41

pH declines as H+ concentration increases

Answer 41

True

Question 42

The lower the pH…

Answer 42

The more acidic

Question 43

Buffer

Answer 43

Is a substance that minimizes changes in the concentrations of H+ and OH- in a solution.

Question 44

How does a buffer work?

Answer 44

It accepts H+ when they are in excess (within the solution) and donates H+ when they have been depleted (to the solution)

Question 45

Most buffers are

Answer 45

Acid/base pairs

Question 46

H2CO3

Answer 46

Buffer that donates H+

Question 47

HCO3-

Answer 47

Buffer that accepts H+

Question 48

Ocean acidification

Answer 48

Occurs when CO2 dissolved in seawater, which forms carbonic acid which lowers ocean pH