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acid
A substance that increases the hydrogen ion concentration of a solution.
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acid precipitation
Rain, snow, or fog that is more acidic than pH 5.6.
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adhesion
The attraction between different kinds of molecules.
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aqueous solution
A solution in which water is the solvent.
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base
A substance that reduces the hydrogen ion concentration of a solution.
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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.
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calorie
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. The Calorie (with a capital C), usually used to indicate the energy content of food, is a kilocalorie.
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celsius scale
A temperature scale (°C) equal to 5/9 (°F - 32) that measures the freezing point of water at 0°C and the boiling point of water at 100°C.
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cohesion
The binding together of like molecules, often by hydrogen bonds.
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colloid
A mixture made up of a liquid and particles that (because of their large size) remain suspended in that liquid. See large intestine.
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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.
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heat
The total amount of kinetic energy due to molecular motion in a body of matter. Heat is energy in its most random form.
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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.
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hydration shell
The sphere of water molecules around each dissolved ion.
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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 a hydrogen ion (H+).
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hydrophilic
Having an affinity for water.
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hydrophobic
Having an aversion to water; tending to coalesce and form droplets in water.
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hydroxide ion
A water molecule that has lost a proton (OH-).
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joule
A unit of energy: 1 J = 0.239 cal; 1 cal = 4.184 J.
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kilocalorie
A thousand calories; the amount of heat energy required to raise the temperature of 1 kg of water by 1°C.
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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.
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molarity
A common measure of solute concentration, referring to the number of moles of solute per liter of solution.
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mole
The number of grams of a substance that equals its molecular weight in daltons and contains Avogadro’s number of molecules.
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molecular mass
The sum of the masses of all the atoms in a molecule; sometimes called molecular weight.
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pH
A measure of hydrogen ion concentration equal to –log [H+] and ranging in value from 0 to 14.
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polar molecule
A molecule (such as water) with opposite charges on opposite sides.
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solute
A substance that is dissolved in a solution.
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solution
A liquid that is a homogeneous mixture of two or more substances.
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solvent
The dissolving agent of a solution. Water is the most versatile solvent known.
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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.
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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.
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temperature
A measure of the intensity of heat in degrees, reflecting the average kinetic energy of the molecules.
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