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.


Acetaldehyde, volatile, colorless, liquid, with a pungent, fruity odor. It is important as an intermediate in the manufacture of many chemicals, pharmaceuticals, and plastics, including acetic acid, butyl alcohol, chloral, and pyridine. Acetaldehyde is miscible (mixable) in all proportions with water and most common organic solvents and is manufactured by the oxidation of ethylene, by the oxidation of ethyl alcohol, or by the combination of water with acetylene. Acetaldehyde melts at -123.5° C (-190.3° F), boils at 20.8° C (69.4° F), and has a density of 0.778 g per ml at 20° C (68° F).