TB Ch. 3 Water and the Fitness of the Environment

32 terms

polar molecule

a molecule (such as water) with opposite charges on opposite ends

cohesion

the binding together of like molecules, often by hydrogen bonds

the attraction between different kinds of molecules

surface tension

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

kinetic energy

the energy of motion, which is directly related to the speed of that motion; moving matter does work by imparting motion to other matter

heat

the total amount of kinetic energy due to molecular motion in a body of matter; energy in its most random form

temperature

a measure of the intesnity of heat in degrees, reflecting the average kinetic energy of the molecules

celsius scale

a temperature scale equal to 5/9 (F - 32) that measures at sea level the freezing point of water at 0 and the boiling point of water at 100, the human body at 37, and room temperature at 20-25

calorie (cal)

the amount of heat energy required to raise the temperature of 1 g of water by 1 degree celsius; also the amount of heat energy that 1 g of water releases when it cools by 1 degree celsius; the Calorie, usually used to indicate the energy content of food, is a kilocalories

kilocalorie

(kcal) a thousand calories; the amount of heat energy required to raise the temperature of 1 kg of water by 1 degree celsius; actual calories on food packages

joule

(J) a unit of energy: 1 J = 0.239 cal; 1 cal = 4.184 J

specific heat

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

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
ex. the hundred fastest runners at a college transferred to another school; the average speed of the remaining students would decline

evaporative cooling

the property of a liquid whereby the surface becomes cooler during evaporation, owing to a loss of highly kinetic molecules to the gaseous state

solution

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

solvent

a dissolving agent of a solution; water is the most versatile solvent known

solute

a substance that is dissolved in a solution

aqueous solution

a solution in which water is the solvent

hydration shell

the sphere of water molecules around each dissolved ion

hydrophilic

having an affinity for water

colloid

a mixture made up of a liquid and particles that (because of their large size) remain suspended in that liquid
ex. cotton does not dissolve but it absorbs water due to cellulose

hydrophobic

having an averasion to water; tending to coalesce and form droplets in water
ex. oil (an ingredient in cell membranes)

molecular mass (molecular weight)

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

mole (mol)

the number of grams of a substance that equals its molecular weight in daltons and contains Avagadro's number of molecules

molarity

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

hydrogen ion

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 ahydrogen ion (H+)

hydroxide ion

(OH-) a water molecule that has lost a proton; OH-

acid

a substance that increases the hydrogen ion concentration of a solution

base

a substance that reduces the hydrogen ion concentration of a solution

pH

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

buffer

a substance that consists of acid and base forms in a solution and that minimizes changes in pH when extraneous acids or bases are added to the solution
ex. keep human blood at a pH of 7.4 using carbonic acid

acid precipitation

rain, snow, or fog that is more acidic than pH 5.6