Chapter 3: Water and Life

Question 1

polar covalent bonds

Answer 1

in a water molecule, the electrons spend more time near the oxygen than the hydrogen

Question 2

polar molecule

Answer 2

a molecule (such as water) with an uneven distribution of charges in different regions of the molecule

Question 3

polarity

Answer 3

• a lack of symmetry
• structural differences in opposite ends of an organism or structure, such as the root end and shoot end of a plant

Question 4

water’s properties

Answer 4

• cohesive behavior
• ability to moderate temperature
• expansion upon freezing
• versatility as a solvent

Question 5

cohesion

Answer 5

the linking together of like molecules, often by hydrogen bonds

Question 6

surface tension

Answer 6

• a measure of how difficult is is to stretch or break the surface of a liquid
• water has a high surface tension because of the hydrogen bonding of surface molecules

Question 7

adhesion

Answer 7

the clinging of one substance to another, such as water to plant cell walls by means of hydrogen bonds

Question 8

kinetic energy

Answer 8

• the energy associated with the relative motion of objects
• moving matter can perform work by imparting motion to other matter

Question 9

thermal energy

Answer 9

• kinetic energy due to the random motion of atoms and molecules\
• energy in its most random form
• aka heat

Question 10

temperature

Answer 10

measure in degrees of the average kinetic energy (thermal energy) of the atoms and molecules in a body of matter

Question 11

heat

Answer 11

thermal energy in transfer from one body of matter to another

Question 12

calorie (cal)

Answer 12

• the amount of heat required to raise the temperature of 1g of water by 1°C
• also the amount of heat energy that 1g of water releases when it cools by 1°C

Question 13

kilocalorie (kcal)

Answer 13

• a thousand calories
• the amount of heat energy required to raise the temperature of 1kg of water by 1°C

Question 14

joule (J)

Answer 14

• a unit of energy
• 1 J = 0.239 cal
• 1 cal=4.184 J

Question 15

specific heat

Answer 15

the amount of heat that must be absorbed or lost for 1g of that substance to change its temperature by 1°C

Question 16

heat is absorbed when…

Answer 16

hydrogen bonds break

Question 17

heat is released when…

Answer 17

hydrogen bonds form

Question 18

evaporation (or vaporization)

Answer 18

transformation of a substance from liquid to gas

Question 19

heat of vaporization

Answer 19

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

Question 20

evaporative cooling

Answer 20

the process in which the surface of an object becomes cooler during evaporation, a result of the molecules with the greatest kinetic energy changing from the liquid to the gaseous state

Question 21

4°C

Answer 21

water reaches its greatest density at ___

Question 22

solution

Answer 22

a liquid that is a homogeneous mixture of two or more substances

Question 23

solvent

Answer 23

the dissolving agent of a solution

Question 24

solute

Answer 24

a substance that is dissolved in a solution

Question 25

aqueous solution

Answer 25

a solution in which water is the solvent (a solution dissolved in water)

Question 26

hydration shell

Answer 26

the sphere of water molecules around a dissolved ion

Question 27

hydrophilic substance

Answer 27

a substance that has an affinity for water

Question 28

hydrophobic substance

Answer 28

• a substance that does not have an affinity for water
• tending to coalesce and form droplets in water (ex: oil)

Question 29

molecular mass

Answer 29

• the sum of all masses of all atoms in a molecule
• aka molecular weight

Question 30

Molarity (M)

Answer 30

a common measure of solute concentration, referring to the number of moles of solute per liter of solution

Question 31

mole (mol)

Answer 31

• the number of grams of a substance that equals its molecular or atomic mass in daltons
• contains Avogadro’s number of the molecules or atoms in question

Question 32

Avogadro’s number

Answer 32

6.02x10^23

Question 33

hydrogen ion (H+)

Answer 33

• a single proton with a charge of 1+
• the dissociation of a water molecule (H2O) leads to the generation of a hydroxide ion (OH-) and a hydrogen ion (H+)
• in water, H+ is not found alone but associates with a water molecule to form a hydronium ion

Question 34

hydroxide ion (OH-)

Answer 34

a water molecule that has lost a proton

Question 35

hydronium ion

Answer 35

• a water molecule that has an extra proton bound to it
• H3O+, commonly represented as H+

Question 36

dynamic equilibrium

Answer 36

water is in a state of _________________ in which water molecules dissociate at the same rate at which they are being reformed

Question 37

acid

Answer 37

a substance that increases the hydrogen ion (H+) concentration of a solution

Question 38

base

Answer 38

a substance that reduces the hydrogen ion (H+) concentration of a solution

Question 39

acidic solutions

Answer 39

solutions with pH values less than 7

Question 40

basic solutions

Answer 40

solutions with pH values greater than 7

Question 41

buffer

Answer 41

• a solution that contains a weak acid and its corresponding base
• minimizes changes in pH when acids or bases are added to the solution

Question 42

ocean acidification

Answer 42

the process by which the pH of the ocean is lowered (made more acidic) when excess CO2 dissolves in seawater and forms carbonic acid (H2CO3)

Question 43

CO2

Answer 43

the main product of fossil fuel combustion

Question 44

calcification

Answer 44

the production of calcium carbonate (CaCO3)

Question 45

water

Answer 45

the most versatile solvent known

Question 46

polar molecule

Answer 46

a molecule (such as water) with an uneven distribution of charges in different regions of the molecule