Beginning of Essay
are the heart of chemistry. People have always known that they exist. The Ancient Greeks were the firsts to speculate on the composition of matter. They thought that it was possible that individual particles made up matter. Later, in the Seventeenth Century, a G ....

Middle of Essay
.... Century Antoine-Laurent Lavoisier, in France, discovered an important detail in the understanding of the chemical reaction combustion of oxygen. He said that combustion was a chemical reaction involving oxygen and another combustible substance, such as wood. John Dalton, in the early Nineteenth Century, discovered the atom. It gave way to the idea that a chemical reaction was actually the rearrangement of groups of atoms called molecules. Dalton also said that the appearance and disappearance of properties meant that the atomic composition gave the appearance of different properties. He also came up with idea that a molecule of one substance ....