Chemistry, the science of the composition of matter, its properties and characteristics, and the changes it undergoes. Chemistry deals with the properties that distinguish one substance from another.

Many people think of chemistry and chemical changes in terms of mysterious experiments conducted in laboratories with strange chemicals and complex apparatus. This is only one aspect of chemistry. Chemical changes are also natural processes and take place all about us.

The burning of coal, gas, and wood; the cooking of meat and other foods; the rusting of a kitchen knife and the tarnishing of silver-all these things which we take for granted involve chemical changes. Life processes such as growth, digestion, and breathing are also examples of chemical change. Many of these changes, which take place in our bodies, are so complex that they cannot yet be duplicated in chemical laboratories.

Important dates in chemistry
c. 3500 B.C. People learned to make bronze.
c. 400 B.C. Democritus proposed an atomic theory.
A.D. 600's Alchemy began to spread from Egypt to the Arabian Peninsula and reached western Europe in the 1100's.
1600's Robert Boyle taught that theories must be supported by careful experiments.
Early 1700's Georg Ernst Stahl developed the phlogiston theory.
1750's Joseph Black identified carbon dioxide.
1766 Henry Cavendish identified hydrogen as an element.
1770's Carl Scheele and Joseph Priestley discovered oxygen.
Late 1700's Antoine Lavoisier stated the law of the conservation of mass and proposed the oxygen theory of combustion.
1803 John Dalton proposed his atomic theory.
1811 Amedeo Avogadro suggested that equal volumes of all gases at the same temperature and pressure contain equal numbers of particles.
Early 1800's Jons J. Berzelius calculated the masses of a number of elements.
1828 Friedrich Wohler made the first synthetic organic substance from inorganic compounds.
1856 Sir William H. Perkin made the first synthetic dye.
1869 Dmitri Mendeleev develops the first modern periodic table. Julius Lothar Meyer independently creates a similar table the following year.
1910 Fritz Haber patented a process to produce synthetic ammonia.
1913 Niels Bohr proposed his model of the atom.
1916 Gilbert N. Lewis described electron bonding between atoms.
1950's Biochemists began to discover how such chemicals as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) affect heredity.
Early 1980's Chemists began working to develop a solar-powered device that produces hydrogen fuel by means of the chemical breakdown of water.
1985 Richard E. Smalley, Robert F. Curl, Jr., and Harold W. Kroto discover buckminsterfullerene, a ball-shaped molecule consisting only of carbon.