Chemical reactionsChemical reactions are at the heart of chemistry. People always knew they existed. The ancient Greeks were the first to speculate on the composition of matter. They thought it was possible for individual particles to constitute matter. Later, in the 17th century, a German chemist named Georg Ernst Stahl was the first to postulate about chemical reaction, particularly combustion. He said a substance called phlogiston escapes into the air from all substances during combustion. He explained that a burning candle would go out if a candle snuffer was placed on it because the air inside the snuffer was saturated with phlogiston. According to his ideas, wood is composed of phlogiston and ash, because only ash remains after combustion. His ideas quickly ran into certain contradictions. When metal is burned, its ashes have a greater mass than the original substance. Stahl tried to cover it up by saying that phlogiston would rob a substance of mass or that it had negative mass, which contradicted his original theories. In the 18th century, Antoine-Laurent Lavoisier, in France, discovered an important detail in understanding the chemical reaction of combustion, oxigin (oxygen). He said combustion was a chemical reaction involving oxygen and another combustible substance, such as wood. John Dalton, at the beginning of the 19th century, discovered the atom. This gave rise to the idea that a chemical reaction was actually a rearrangement of groups of atoms called molecules. Dalton also stated that the appearance and disappearance of properties meant that atomic composition dictated the appearance of different properties. He also came up with the idea that one molecule of a substance is exactly the same as any other molecule of the same substance. People like Joseph-Lois Gay-Lussac added to Dalton's concepts the postulate that the volumes of gases reacting with each other are related (14 grams of nitrogen reacted with exactly three grams of hydrogen, eight grams of (oxygen reacted with exactly one gram of hydrogen, etc.) Amedeo Avogadro also contributed to the understanding of chemical reactions. He said that all gases at the same pressure, volume and temperature contain the same number of particles. This idea took a long time to be accepted. His ideas lead to the subscripts used in formulas f...... middle of paper ......st, stimulating a reaction between two reactants, simply stimulating a reaction one molecule at a time. The molecules are stimulated in a pattern that gives the desired results. This discovery opens the doors to nanoengineering and materials sciences. This gives a good idea of ​​what is happening, one molecule at a time. Chemical reactions make up a large part of chemistry. This article is an overview of this broad topic. This gives a good idea of ​​the history of chemical reactions as well as the future. Let us hope that the expansion of chemistry and our knowledge will not cease. Since scientists are still experimenting, chemical reactions will always be part of chemistry.Bibliography “Chemical Reactions”, Encyclopedia Brittanica MACROPEDIA, 1995, Vol. 15 “Dances with molecules”, Science News, Vol. 147, May 27, 1995Eastman, Richard H., General Chemistry: Experimental and Theory, Holt, Rhinehart and Winston Inc., 1970 "One Molecule at a Time", Discover, January 1996Pauling, Linus and Peter, Chemistry, WH Freeman and Co. , 1975 “Chemical reactions”, Encyclopedia Americana, 1982, Vol. 23 “Chemical reactions”, Academic American Encyclopedia, 1991, Vol.. 16