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.

Avogadro's Law of Gas

The behavior of gases described by Boyle’s, Charles’s, and Dalton’s laws is nearly the same for all gases. Avogadro’s law states that under identical conditions of temperature and pressure, equal volumes of different gases contain equal numbers of particles (atoms or molecules).

The temperature 0ºC (32ºF) and the pressure equal to the pressure Earth’s atmosphere exerts at sea level are called standard temperature and pressure (STP). According to Avogadro’s law, 1 cubic meter of oxygen at STP contains the same number of particles as 1 cubic meter of nitrogen at STP. Restated, Avogadro's law says that one mole of any gas at STP occupies a volume of 22.4 liters. A mole is basic particles (atoms or molecules) of a substance. The extremely large number is called Avogadro's number.