water and life

Electronegativity

The attraction of a given atom for the electrons of a covalent bond.

Polar Molecule

A molecule with opposite charges on different ends of the molecule.

Cohesion

The binding together of like molecules, often by hydrogen bonds.

Adhesion

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. Example: Water has a high level of it because of the hydrogen bonding of surface molecules.

Kinetic Energy

The engergy associated with the relative motion of objects. Moving matter can perform work by imparting motion to other matter. Example: The faster the molecule moves, the greater it is.

Heat

The total amount of kinetic energy due to the random motion of atoms or molecules in a body of matter; It is energy in in its most random form. Example: For a given body of matter, the amount of it is

Temperature

A measure of the intensity of heat in degrees, reflecting the average kinetic energy of the molecules.

Celsius Scale

A temperature scale that measures the freezing point of water at 0 C and the boiling point of water at 100 C.

Calories (cal)

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

Kilocalorie (kcal)

A thousand calories; the amount of heat energy required to raise the temperature of 1 kg of water by 1 C.

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 C. A measure of how well a substance resists changing its temperature when it absorbs or releases

Heat of Vaporization

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

Evaporative Cooling

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

Solution

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

Solvent

The dissolving agent of a solution. Example: Water is the most versatile one 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 a 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 rather than dissolved in that liquid.

Hydrophobic

Having an aversion to water; tending to coalesce and form droplets in water.

Molecular Mass

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

Mole (mol)

The number of grams of a substance that equals its molecular weight in daltons and contains Avogadro's number of molecules.

Molarity

A common measure of solute concentration, referring to the number of moles of solute per liter of solution. The unit of concentration most often used by biologist for aqueous solutions.

Hydrogen Ion (H+)

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+)

Hydroxide Ion (OH-)

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

Hydronium Ion (H3O+)

A water molecule that has an extra proton bound to it; (H3O+).

Acid

A substance that increasese 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.

Buffers

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.

Acid Precipitation

Rain, snow, or fog that is more acidic than pH 5.2.