AP BIO FINAL - CHAPTER 3

What is the relevance of water's high specific heat to life on Earth?

A large body of water can absorb and store a huge amount of heat from the sun in the daytime and during summer while warming up only a few degrees. At night and during winter, the gradually cooling water can warm the air. This capability of water serves to moderate air temperatures in coastal areas.

evaporative cooling

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.

hydrophilic

having an affinity for water; water loving

hydrophobic (ex: oil)

having no affinity for water; tending to coalesce and form droplets in water.

When an ionic compound is dissolved in water, each ion is surrounded by a

hydration shell: the sphere of water molecules around a dissolved ion

Ice floats in liquid water because

hydrogen bonds in ice are more "ordered" - the hydrogen bonds keep the molecules at "arm's length" with trapped air in between, far enough apart to make ice about 10% less dense

Even large polar molecules such as proteins can dissolve in water if they have _________ and polar regions

ionic

Water is the most versatile solvent known due to

its polarity

thermal energy

kinetic energy due to the random motion of atoms and molecules; energy in its most random form

Because of the high specific heat of water relative to other materials, water will change its temperature _______ than other liquids when it absorbs or loses a given amount of heat.

less

Water has three forms:

liquid, solid (ice), and gas (water vapor)

Water can also dissolve compounds made of

nonionic polar molecules by surround each of the solute molecules and forming hydrogen bonds with them.

concentrations of H+ and OH- are equal in

pure water

Water is less dense as a ________ than as a liquid

solid (ice floats on liquid water) - greatest density at 4°C

neutral solutions

solutions in which [H+] and [OH-] are equal; a pH equal to 7

acidic solutions

solutions with a higher concentration of [H+] than [OH−]; a pH scale value LESS than 7

basic solutions

solutions with a higher concentration of hydroxide ions [OH−] than hydrogen ions [H+]; a pH scale value GREATER than 7

thermal energy vs temperature

temperature represents the AVERAGE kinetic energy of the molecules in a body of matter, regardless of volume, whereas the thermal energy of a body of matter reflects the TOTAL kinetic energy, and depends on the matter's volume.

calorie (cal)

the amount of heat it takes to raise the temperature of 1 g of water by 1°C

adhesion

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

kilocalorie (kcal)

(1000 calories) the quantity of heat required to raise the temperature of 1 kilogram (kg) of water by 1°C

water's four emergent properties

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

Water's high specific heat can be traced to hydrogen bonding

- Heat is absorbed when hydrogen bonds break - Heat is released when hydrogen bonds form

why is the ability of ice to float important in the suitability of the environment for life?

If ice sank, then eventually all ponds, lakes, and even oceans would freeze solid, making life as we know it impossible on Earth.

specific heat

The amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1°C; can be thought of as a measure of how well a substance resists changing its temperature when it absorbs or releases heat.

explain how 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 (H+) - the molecule that lost the proton is now a hydroxide ion (OH-) - the molecule with the extra proton is now a hydronium ion (H3O+), though it is often represented as H+

pH

A measure of hydrogen ion concentration equal to -log [H+] and ranging in value from 0 to 14.

joule (J)

A unit of energy: 1 J = 0.239 cal; 1 cal = 4.184 J.

The properties of water arise from attractions between oppositely charged atoms of different water molecules:

The partially positive hydrogen of one molecule is attracted to the partially negative oxygen of a nearby molecule. The two molecules are thus held together by a hydrogen bond

molecular mass

The sum of the masses of all the atoms in a molecule; sometimes called molecular weight

explain how cohesion contributes to the transport of water and dissolved nutrients against gravity in plants

Water from the roots reaches the leaves through a network of water-conducting cells. As water evaporates from a leaf, hydrogen bonds cause water molecules leaving the veins to tug on molecules farther down, and the upward pull is transmitted through the water-conducting cells all the way to the roots.

molarity

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

solution

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

temperature

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

surface tension

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

polar molecule

a molecule with an uneven distribution of charges in different regions of the molecule

aqueous solution

a solution in which water is the solvent

buffer

a solution that contains a weak acid and its corresponding base, which combine reversibly with [H+] ions. A buffer minimizes changes in pH when acids or bases are added to the solution

base

a substance that decreases the hydrogen ion concentration of a solution.

acid

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

solute

a substance that is dissolved in a solution.

Why does ice float in liquid water? a. Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water b. Ice always have air bubbles that keep it afloat c. The liquid water has more kinetic energy and support the ice d. The ionic bonds between the ice molecules prevent the ice from sinking

a. Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water

Liquid water a. has a heat of vaporization higher than most other substances b. is nonpolar c. is less dense than ice d. has a specific heat lower than most other substances

a. has a heat of vaporization higher than most other substances

Hydrophobic substances such as vegetable oil are a. nonpolar substances that repel water molecules b. charged molecules that hydrogen bond to water molecules c. nonpolar substances that have an attraction to water molecules d. polar substances that repel water molecules

a. nonpolar substances that repel water molecules

explain the role of adhesion in plants

adhesion of water by hydrogen bonds to the molecules of cell walls helps counter the downward pull of gravity

Which of the following is true when an ice cube cools a drink? a. Kinetic energy in the drink decreases b. A calorie of heat energy transfers from the ice cube to the water of the drink c. Molecule collisions in the drink increase d. The specific heat of the water in the drink decreases

b. A calorie of heat energy transfers from the ice cube to the water of the drink

Which of the following is possible due to the high surface tension of water? a. Lakes don't freeze solid in winter even with low temperatures b. A water strider can walk across the surface of a pond c. Organisms resist temperature changes, although they give off heat in chemical reactions d. Water can act as a solvent

b. A water strider can walk across the surface of a pond

Why is a steam burn more severe than a hot water burn? a. Water evaporates and leaves the surface faster which helps in cooling b. Steam contains more energy than water c. Steam can penetrate into the skin d. Burns caused by liquids are always milder

b. Steam contains more energy than water

If the cytoplasm of a cell is a pH of 7 and the mitochondrial matrix is a pH of 8, then the concentration of H+ ions a. in the cytoplasm is 7/8 the concentration of the mitochondrial matrix b. is 10 times higher in the cytoplasm than in the mitochondrial matrix c. is 10 times higher in the mitochondrial matrix than in the cytoplasm d. in the cytoplasm is 8/7 the concentration of the mitochondrial matrix

b. is 10 times higher in the cytoplasm than in the mitochondrial matrix

We can be sure that a mole of table sugar and a mole of vitamin C are equal in their a. volume b. number of molecules c. mass d. number of atoms

b. number of molecules

Water is able to form hydrogen bonds because a. oxygen has a valence of 2 b. the bonds that hold together the water molecule are polar covalent bonds c. the water molecule is shaped like a tetrahedron d. the oxygen atom has a weak negative charge

b. the bonds that hold together the water molecule are polar covalent bonds

Water's high specific heat is mainly a consequence of the a. high specific heat of the hydrogen and water atoms b. inability of water to dissipate heat into dry air c. absorption and release of heat when hydrogen bonds break and form d. small size of the molecules

c. absorption and release of heat when hydrogen bonds break and form

Thermal energy of the water in a bathtub is ________ than in a freshly brewed coffee pot because of its _______. a. higher; high kinetic energy b. lower; low temperature c. higher; greater volume d. lower; low density

c. higher; greater volume

An example of a hydrogen bond is the bond between a. Na+ and Cl- in salt b. C and H in methane (CH4) c. the H in one water molecule and the O in another water molecule d. the two hydrogen atoms in a molecule of hydrogen gas (H2)

c. the H in one water molecule and the O in another water molecule

The formation of ice during colder weather helps moderate the seasonal transition winter. This is mainly because a. ice is denser than liquid water b. the breaking of hydrogen bonds absorbs heat c. the formation of hydrogen bonds releases heat d. the formation of hydrogen bonds absorbs heat

c. the formation of hydrogen bonds releases heat

Which of the following is a hydrophobic material? a. sugar b. table salt c. wax d. paper

c. wax

A 0.01M solution of substance has a pH of 2. What can you conclude about this substance? a. It is a weak acid b. It is a weak base c. It is a strong base that dissociates completely in water d. It is a strong acid that dissociates completely in water

d. It is a strong acid that dissociates completely in water

Increased atmospheric CO2 concentrations may have what effect on seawater? a. Seawater will become more acidic and carbonate concentrations will increase b. There will be no change in the pH of seawater because carbonate will turn into bicarbonate c. Seawater will become more alkaline and carbonate concentrations will decrease d. Seawater will become more acidic and carbonate concentrations will decrease

d. Seawater will become more acidic and carbonate concentrations will decrease

Which are the following statements are true regarding buffer solutions? a. They maintain a constant pH of 7 b. They maintain a constant pH when acids are added to them but not when bases are added to them c. They fluctuate in pH when either acids or bases are added to them d. They maintain a relatively constant pH when either acids or bases are added to them

d. They maintain a relatively constant pH when either acids or bases are added to them

Desert rabbits are adapted to the warm climate because their large ears aid in the removal of heat due to the a. high specific heat of water b. buffering capacity of water c. high surface tension in water d. high heat of vaporization of water

d. high heat of vaporization of water

What determines the cohesiveness of water molecules? a. hydrophobic interactions b. ionic bonds c. nonpolar covalent bonds d. hydrogen bonds

d. hydrogen bonds

Which of the following solutions has the greatest concentration of hydroxide ions [OH-]? a. tomato (pH 4) b. urine (pH 6) c. lemon juice (pH 2) d. seawater (pH 8)

d. seawater (pH 8)

Rank from low to high, the pH of blood, urine and stomach acid. a. stomach acid, blood, urine b. blood, urine, stomach acid c. urine, blood, stomach acid d. stomach acid, urine, blood

d. stomach acid, urine, blood

how does the evaporative cooling stabilize temperatures in organisms and bodies of water?

evaporation of water from the leaves of a plant helps keep the tissues in the leaves from becoming too warm in the sunlight. Evaporation of sweat from human skin dissipates body heat and helps prevent overheating on a hot day or when excess heat is generated by strenuous activity.

solvent

the dissolving agent of a solution.

kinetic energy

the energy associated withe the relative motion of objects. Moving matter can perform work by imparting motion to other matter

water in its liquid form

the hydrogen bonds become very fragile, each only about 1/20 as strong as a covalent bond. The hydrogen bonds form (lasts only a few trillionths of a second), break, and re-form with great frequency.

mole (mol)

the number of grams of a substance that equals its molecular or atomic mass in daltons; contains 6.02 x 10^23 representative particles of that substance

ocean acidification

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).

heat of vaporization

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

cohesion

the sticking together of similar molecules, often by hydrogen bonds

vaporization or evaporation

the transformation from a liquid to a gas

heat

thermal energy in transfer from one body of matter to another

Whenever two objects of different temperature are brought together,

thermal energy passes from the warmer to the cooler object until the two are the same temperature

water's high heat of vaporization

to evaporate 1 g of water at 25°C, about 580 cal of heat is needed

water molecule = (polar molecule)

two hydrogen atoms joined to an oxygen atom by single covalent bonds. Oxygen is more electronegative than hydrogen, so the electrons of the covalent bonds spend more time closer to oxygen than to hydrogen (polar covalent bonds). the oxygen of the molecule has two regions of partial negative charge (δ-), and each hydrogen has a partial positive charge (δ+)

water's surface tension

unusually high due to hydrogen bonding between molecules at the air-water interface and the water below

specific heat of water

unusually high; 1 cal/(g ⋅°C)