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.

Crystal

Crystal (mineral), homogeneous portion of matter that has a definite, orderly atomic structure, and an outward form bounded by smooth, plane surfaces, symmetrically arranged. Crystals are produced whenever a solid is formed gradually from a fluid, whether the formation results from the freezing of a liquid, the deposition of dissolved matter, or the direct condensation of a gas into solid form. The angles between corresponding faces of any two crystals of the same substance, regardless of size or superficial difference of form, are always identical

Most solid matter displays orderly atomic arrangement and is of crystalline structure. Solids that have no crystalline structure, such as glass, are called amorphous. In structure they show greater similarity to liquids than to solids.