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.

Acrylic

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Acrylic, chemical name for the organic group, which occurs in acrylic acid and in the esters of this acid, called acrylates, such as methyl acrylate. Acrylic resins, often called acrylics, are made by the polymerization of acrylates or other monomers containing the acrylic group. Acrylic compounds are thermoplastic (able to soften or fuse when heated and reharden upon cooling), impervious to water, and have low densities. These qualities make them suitable for the manufacture of a variety of objects and substances, including molded structural materials, adhesives, and textile fibers. Such fibers are used to weave durable, easily laundered fabrics that resist shrinkage. Acrylic paints—emulsions of pigments, water, and clear, nonyellowing acrylic resins—dry quickly without changing color and do not darken with time.