Matter & Energy

Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.


Alcohol (Arabic al-kuhul), term applied to members of a group of chemical compounds and, in popular usage, to the specific compound ethyl alcohol, or ethanol. The Arabic word denotes kohl, a fine powder of antimony used as an eye makeup. The word alcohol originally denoted any fine powder; the alchemists of medieval Europe later applied it to essences obtained by distillation, and this led to the current usage.

Alcohols are a class of organic compounds containing the hydroxyl group, OH, attached to a carbon atom. Alcohols have one, two, or three hydroxyl groups attached to their molecules and are thus classified as monohydric, dihydric, or trihydric, respectively. Methanol and ethanol are monohydric alcohols. Alcohols are further classified as primary, secondary, or tertiary, according to whether one, two, or three other carbon atoms are bound to the carbon atom to which the hydroxyl group is bound. Alcohols, although analogous to inorganic bases, are neither acid nor alkaline. They are characterized by many common reactions, the most important of which is the reaction with acids to form substances called esters, which are analogous to inorganic salts. Alcohols are normal by-products of digestion and chemical processes within cells and are found in the tissues and fluids of animals and plants.

See Wood Alcohol; Grain Alcohol; Higher Alcohol; Types of Alcohol.