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.


Apatite (Greek apate, “deception”), mineral so named because it resembles various other minerals for which it might be mistaken. It consists chiefly of phosphate of lime. Apatite is a distinct mineral of composition in which some or all of the fluorine may be replaced by chlorine (chlorapatite). The mineral crystallizes in the hexagonal system (see Crystal) and has a hardness of 5 and a specific gravity of 3.2. When pure, apatite is colorless and transparent, but it may exhibit various degrees of color and opacity. These mineral phosphates of lime were often used in the preparation of fertilizers, but they have been replaced by phosphate rock.