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.


Phenol, formerly called carbolic acid, aromatic organic compound. It is weakly acidic and resembles the alcohols in structure. The colorless, needlelike crystals of purified phenol melt at 43° C (109° F) and boil at 182° C (360° F). During storage the crystals become pink and finally reddish brown. Phenol is soluble in organic solvents and slightly soluble in water at room temperature, but infinitely soluble above 66° C (150.8° F). It is a constituent of coal tar.

Phenol was first used as a disinfectant in 1867 by the British surgeon Joseph Lister for sterilizing wounds, surgical dressings, and instruments. Dilute solutions are useful antiseptics, but strong solutions are caustic and scarring to tissue. Less irritating and more efficient germicides have replaced phenol, but it is widely used in the manufacture of resins, plastics, insecticides, explosives, dyes, and detergents, and as raw material for the production of medicinal drugs such as aspirin.

A phenol derivative, phenolphthalein is a chemical compound prepared by a reaction between phenol and phthalic anhydride in the presence of sulfuric acid; it is used as an indicator for acidity or alkalinity.

The term phenol is also used for any of a group of related acidic compounds that are hydroxyl derivatives of aromatic hydrocarbons, such as cresols and resorcinol.