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.


Biomass, contraction for biological mass, the amount of living material provided by a given area of the earth's surface. The term is most familiar from discussions of biomass energy, that is, the fuel energy that can be derived directly or indirectly from biological sources. Biomass energy from wood, crop residues, and dung remains the primary source of energy in developing regions. In a few instances it is also a major source of power, as in Brazil, where sugarcane is converted to ethanol fuel, and in China's Sichuan province, where fuel gas is obtained from dung. Various research projects aim at further development of biomass energy, but economic competition with petroleum has mainly kept such efforts at an early developmental stage.

See Synthetic Fuels; Gasohol.