A chemist is a scientist trained in the science of chemistry. Chemists study the composition of matter and its small-scale properties such as density and acidity instead of large-scale properties like size and shape. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms. Chemists carefully measure substance proportions, reaction rates, and other chemical properties.
Chemists use this knowledge to learn the composition, and properties of unfamiliar substances, as well as to reproduce and synthesize large quantities of useful naturally occurring substances and create new artificial substances and useful processes. Chemists may specialize in any number of subdisciplines of chemistry. Materials scientists and metallurgists share much of the same education and skills with chemists. Chemical engineers are concerned with the physical processes necessary to carry out industrial reactions (heating, cooling, mixing, diffusion etc) and to separate and purify the products, and work with industrial chemists on the development of new processes.
The roots of chemistry can be traced to the phenomenon of burning. Fire was a mystical force that transformed one substance into another and thus was of primary interest to mankind. It was fire that led to the discovery of iron and glass. After gold was discovered and became a precious metal, many people were interested to find a method that could convert other substances into gold. This led to the protoscience called Alchemy. The word chemist is derived from the New Latin noun chimista, an abbreviation of alchimista (alchemist). Alchemists discovered many chemical processes that led to the development of modern chemistry. Chemistry as we know it today, was invented by Antoine Lavoisier with his law of Conservation of mass in 1783. The discoveries of the chemical elements has a long history culminating in the creation of the periodic table by Dmitri Mendeleyev. The Nobel Prize in Chemistry created in 1901 gives an excellent overview of chemical discovery since the start of the 20th century.
Chemistry typically is divided into several major sub-disciplines. There are also several main cross-disciplinary and more specialized fields of chemistry. There is a great deal of overlap between different branches of chemistry, as well as with other scientific fields such as biology, medicine, physics, and several engineering disciplines.
All the above major areas of chemistry employ chemists. Other fields where chemical degrees are useful include Astrochemistry, Atmospheric chemistry, Chemical Engineering, Chemo-informatics, Electrochemistry, Environmental science, Forensic science, Geochemistry, Green chemistry, History of chemistry, Materials science, Medical science, Molecular Biology, Molecular genetics, Nanotechnology, Nuclear chemistry, Oenology, Organometallic chemistry, Petrochemistry, Pharmacology, Photochemistry, Phytochemistry, Polymer chemistry, Supramolecular chemistry and Surface chemistry.
It has been suggested that chemists going into employment in scientific research should honour a Hippocratic Oath for Scientists.