Chemistry (derived from alchemy) is the science of matter at or near the atomic scale. In this pursuit, chemistry deals with the structure and properties of such matter, the transformations of matter and the interactions of matter with other matter and with energy. Chemistry primarily studies atoms and collections of atoms such as molecules, crystals or metals that make up ordinary matter. According to modern chemistry it is the structure of matter at the atomic scale that is determinant of the nature of any given matter (See reductionism and quantum mechanics). It is, with physics, one of the most fundamental of all natural science.

Chemical reaction
A Chemical reaction is a process that results in the interconversion of chemical substances. Such reactions can result in molecules attaching to each other to form larger molecules, molecules breaking apart to form two or more smaller molecules, or rearrangement of atoms within or across molecules. Chemical reactions usually involve the making or breaking of chemical bonds. For example, substances that react with oxygen to produce other substances are said to undergo oxidation; similarly a group of substances called acids or alkalis can react with one another to neutralize each other's effect, a phenomenon known as neutralization. Substances can also be dissociated or synthesized from other substances by various different chemical processes.