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Flashcards in Unit 2 Deck (42):
1

polar molecule

a molecule that's overall charge is unevenly distributed

2

polarity of molecules

oxygen part is slightly negative, hydrogens are slightly positive
-allows water particles to be held together by hydrogen bonds
-high surface tension

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Properties of Water

-Polar
-Cohesion of Water Molecules
-Moderation of Temperature
-high specific heat
-high heat of vaporization
-Ice less dense than liquid

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Cohesion

linking together of molecules of the same substance by hydrogen bonds

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Cohesion of Water Molecules

-along with adhesion allows water to be transported against gravity in plant
-great surface tension

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Surface tension

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

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Heat

a measure of the matter's total kinetic energy due to motions of its molecules
-depends on volume

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Temperature

measure of heat intensity that represents the average kinetic energy of molecules

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calorie

the amount of heat it takes to raise the temp of 1g of water 1 degree Celsius .

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specific heat

the amount of heat that must be absorbed or lost for 1g of that substance to change 1 degree Celsius

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Water's high specific heat

-water's temp will change less when it absorbs or loses heat
-high because hydrogen bonds are first formed or broken by energy before the kinetic energy of the molecules are affected
-keeps temp fluctuations on land and water within limits that permit life
- allows organisms (who are made up mostly of water) to resist changes in their own temp

12

Heat of Vaporization

the quantity of heat a liquid must absorb for 1g of it to be converted from liquid to gas
-water high level: helps moderate Earth's climate

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evaporative cooling

as a liquid evaporates, the surface of remaining liquid cools (hottest molecules evaporate)
-contributes to stable temps in lakes and ponds
-prevents terrestrial organisms from overheating (evaporation from leaves, sweat)

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Floating of Ice on Liquid water

- one of few substances that are less dense as a solid than a liquid
-ice molecules each hydrogen bonded to 4 neighbors in spacious crystal
-ice insulates liquid water below, preventing it from freezing and allowing life to exist under the surface
- provides solid habitat for some animals

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aqueous solution

a solution in which water is the solvent

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hydration shell

water molecules surround dissolved ions forming a sphere

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hydrophilic

any substance that has an affinity for water

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colloid

a stable suspension of fine particles in a liquid

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hydrophobic

substances that are non-ionic and non polar and seem to repel water

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molecular mass

sum of the masses of all atoms in a molecule

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mole

equal to the molecular mass, the amount of a substance that contains 6.02x10^23 molecules

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molarity

the number of moles of solute per liter of solution

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hydrogen ion

H+ a single proton with charge of 1+

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hydroxide ion

OH- charge of -1

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hydronium ion

H3O+ represents by H+

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acid

a substance that increases the hydrogen ion concentration of a solution

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acidic solution

a solution that has more H+ than OH-

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base

a substance that reduces the hydrogen ion concentration of a solution

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basic solution

more OH- than H+

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The PH scale

-at room temperature 25 C:
- [H+][OH-]= 10^-14
pH= -log[H+}
- less than 7 equals acid 7= neutral greater than 7 basic

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Buffers

a substance that minimizes changes in the concentrations of H+ and OH- in a solution
- accepts excess H+ or donates H= when developed from a solution
- carbonic acid (H2CO2) is one found in blood
-often acid base pairs

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ocean acidification

occurs when CO2 dissolves in seawater, reacts and forms carbonic acid, lower pH
-limits calcification (which is important for coral reefs)

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acid precipitation

refers to rain, snow, or fog with a pH lower than 5.2

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carbon

has 4 valence electrons and shares these electrons to get 8 valence electrons
-when 4 single bonds are formed the molecule forms a tetrahedral shape
-two carbons that have a double bond form a flat rectangular shape

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organic molecules

made up mostly of carbon, hydrogen, oxygen, and nitrogen

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Carbon skeletons can vary in;

length, branching, double bond position, presence of rings

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hydrocarbons

organic molecules consisting of only carbon and hydrogen
-major components of petroleum
-many of cells organic molecules have regions of hydrocarbons, ex. fat molecules tails
-relatively nonpolar, often behave hydrophobically
- can undergo reactions that release large amounts of energy

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Isomers

compounds that have the same number of atoms of the same elements but different structures and thus different properties

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structural isomers

differ in the covalent arrangements of their atoms and the location of double bonds

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cis-trans isomers

carbons have covalent bonds to the same atoms but these atoms differ in their spatial arrangement due to the inflexibility of double bonds
- cis isomer; both x atoms on the same side of the double axis
-trans isomer; x's on opposite sides

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Enantiomers

isomers that are mirror images of each other and that differ in shape due to the presence of an asymmetric carbon
-can cause drugs to have different effects

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asymmetric carbon

a carbon that is attached to four different atoms.