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.


Caffeine, an alkaloid found in coffee, tea, cacao, and some other plants. It is also present in most cola beverages. Caffeine was discovered in coffee in 1820. In 1838 it was established that theine, discovered in tea in 1827, is identical to caffeine. The drug increases the blood pressure, stimulates the central nervous system, promotes urine formation, and stimulates the action of the heart and lungs. Caffeine is used in treating migraine because it constricts the dilated blood vessels and thereby reduces the pain. It also increases the potency of analgesics such as aspirin, and it can somewhat relieve asthma attacks by widening the bronchial airways. Caffeine is produced commercially chiefly as a by-product in making caffeine-free coffee.

Caffeine has been suggested as a possible cause of cancer or of birth defects. No studies, however, have yet confirmed any of these charges. Persons who stop drinking coffee do sometimes experience withdrawal headaches. The U.S. Food and Drug Administration does not include caffeine on its “generally recognized as safe” (GRAS) list, but acknowledges no clear evidence of hazard at normal levels of use.