What is Chemistry ?
Definition of Chemistry:
Chemistry is the science of matter, that is, of all physical substances including gases and liquids as well as solids, and the changes that occur between different kinds of matter especially chemical changes (called 'reactions') when types of matter are re-arranged into other types of matter e.g. water splitting into the gases hydrogen and oxygen.
That is, chemistry is a physical science concerned with the composition, structure, behaviour, and properties of matter and with the changes it undergoes during, and as a result of, chemical reactions. It involves study of substances in all of the the states of matter (solid, liquid and gas) and knowledge and understanding of the various structures of matter (incl. e.g. atoms, molecules, crystals and other aggregates) whether in isolation or in combination with others.
Major Branches of Chemistry
Chemistry is a huge subject within which there are several 'branches', i.e. topics or areas of study that are distinctive, recognised, parts of the overall subject of chemistry. It is not possible to answer the question What is Chemistry ? without reference to particular types of chemistry.
Introductory (school-level) chemistry cannot include all branches of chemistry, some of which are highly specialised. However, even at secondary school level students aged 14-16 may study chemistry in terms of the three main categories of Physical Chemistry, Inorganic Chemistry and Organic Chemistry. Examples of topics included in each of these areas are listed below.
Other Branches of Chemistry
Other, in many cases highly specialised, disciplines within chemistry are also important and are often named according to the context or manner in which understanding of matter is important.
The specialties mentioned above do not form a complete list but help to convey a broad impression of What is Chemistry?
In some cases there are many more sub-specialties within these areas. The above gives a general impression of the wide scope of chemistry and the contexts in which it is important.
Comparison with other Science subjects:
Comparison between Chemistry and Physics
Some aspects of the structure and behaviour of matter are also described by the associated science of physics, but with different emphasis: Chemistry is concerned with the composition, structure, behaviour, and properties of matter, and with the changes it undergoes during and as a result of chemical reactions. Physics is generally more concerned with the observable or measurable effects of changes in or to bulk materials, e.g. as described by the Laws of Motion, Law of Gravity, electricity, magnetism, optics, etc..
Chemistry and physics interface and even overlap in some areas of study, e.g. concerning sub-atomic particles, radiation, and aspects of atmospheric and environmental research. Chemistry makes use of aspects of physics in areas of physical chemistry and contributes to physics in many ways, e.g. re. various types of protective coatings for surfaces and concerning colour, such as for optical components and filters, coatings, etc..
Comparison between Chemistry and Biology
Biology is the physical (including chemical) study of life and living things.
It includes human biology (which is associated with medicine and its specialties), zoology (i.e. animal life, associated subjects being veterinary science and its specialties) and botany (concerning plant life). It is described here as a 'physical' study of 'life' to distinguish it from disciplines interested in life from other perspectives, such as anthropology, sociology, philosophy, ethics, and the many religious and other (less structured / hierarchical, but also) 'spiritual' approaches to the concept of life and experience of it.
In common with biology, chemistry attempts to describe and explain matter, living or otherwise, in terms of its composition, structure, properties, and so on. Aspects of the structure and behaviour of living matter and matter formed by living organisms are also described by the associated science of biology, hence the interface and overlap between chemistry and biology, which is called biochemistry. Biochemistry is not usually offered as a separate subject in its own right at introductory level, such as in schools and colleges. This is because it is necessary to have a good basic understanding of both biology and chemistry in order to understand some of the more advanced issues at the interface of the two subjects. Another discipline that uses knowledge of both introductory chemistry and biology is microbiology.
A good understanding of at least introductory chemistry is extremely useful for appreciating advanced biology generally because (in physical terms), all living things ultimately consist of the atoms and molecules described and explained by courses in school-level chemistry and beyond. Conversely, knowledge of biology is not essential for appreciation of all areas of advanced chemistry. For example, industrial processes e.g. in the automotive and plastics industries, require advanced chemistry for applications unrelated to living organisms. However, even then, some understanding of biology may be useful e.g. for health and safety issues or for responsible sourcing of raw materials.