Chapter 3: Water and Life Flashcards
Hydrogen ion
A single proton with a charge of plus one. The dissociation of a water molecule leads to the generation of a hydroxide ion (with a charge of minus one) and a hydrogen ion (with a charge of plus one); in water, the hydrogen ion is not found alone but associates with a water molecule to form a hydronium ion.
Hydration shell
The sphere of water molecules around a dissolved ion.
Hydrophilic
Having an affinity for water.
Mole
The number of grams of a substance that equals its molecular or atomic mass in daltons; a mole contains Avogadro’s number of the molecules or atoms in question.
Buffer
A solution that contains a weak acid and its corresponding base. A buffer minimizes changes in pH when acids or bases are added to the solution.
Acid
A substance that increases the hydrogen ion concentration of a solution.
Molarity
A common measure of solute concentration, referring to the number of moles of solute per liter of solution.
PH
A measure of hydrogen ion concentration equal to the negative log of the concentration of hydrogen ions and ranging in value from 0 to 14.
Kilocalorie
(kcal) A thousand calories; the amount of heat energy required to raise the temperature of 1 kg of water by 1 degree C.
Hydroxide ion
A water molecule that has lost a proton, represented as OH superscript minus.
Hydrophobic
Having no affinity for water; tending to coalesce and form droplets in water.
Hydronium ion
A water molecule that has an extra proton bound to it, commonly represented as H superscript plus.
Aqueous solution
A solution in which water is the solvent.
Heat
Thermal energy in transfer from one body of matter to another.
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 surface molecules.
Base
A substance that reduces the hydrogen ion concentration of a solution.
Joule
(J) A unit of energy: 1 J equals 0.239 cal; 1 cal equals 4.184 J.
Solution
A liquid that is a homogeneous mixture of two or more substances.
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.
Solute
A substance that is dissolved in a solution.
Molecular mass
The sum of the masses of all the atoms in a molecule; sometimes called molecular weight.
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 C.
Solvent
The dissolving agent of a solution. Water is the most versatile solvent known.
Temperature
A measure in degrees of the average kinetic energy (thermal energy) of the atoms and molecules in a body of matter.
Polar molecule
A molecule (such as water) with an uneven distribution of charges in different regions of the molecule.
Adhesion
The clinging of one substance to another, such as water to plant cell walls, in this case by means of hydrogen bonds.
Cohesion
The linking together of like molecules, often by hydrogen bonds.
Kinetic energy
The energy associated with the relative motion of objects. Moving matter can perform work by imparting motion to other matter.
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.
Calorie
(cal) The amount of heat energy required to raise the temperature of 1 g of water by 1 degree C; also the amount of heat energy that 1 g of water releases when it cools by 1 degree C. The Calorie (with a capital C), usually used to indicate the energy content of food, is a kilocalorie.
Thermal energy
Kinetic energy due to the random motion of atoms and molecules; energy in its most random form; Thermal energy in transfer from one body of matter to another.
Ocean acidification
The process by which the pH of the ocean is lowered (made more acidic) when excess carbon dioxide dissolves in seawater and forms carbonic acid.
