The study of the relationships between energy and matter. The two major divisions are: Newtonian (classical) physics and modern (particle) physics.
Prior to 1687 it was believed that the natural state of a body was at rest. This theory was blown apart by Newton in his book Principa Mathematica in which it was demonstrated that the natural state of a body was in motion (See Newtons Laws of Motion). So important was this theory that it became the basis of all future physics research.
The cornerstones of modern physics are Quantum Theory and Relativity. They are based on the theories and concepts developed since 1900 and affect all aspects of scientific research. Much of modern physics is involved with the properties and behaviour of sub-atomic particles.
Chemistry is the scientific study of the composition and changes in substances. The main divisions are: biochemistry (living organisms), organic chemistry (carbon and its compounds) and inorganic chemistry (elements and compounds other than carbon).
The chemical composition of any substance is defined by the numbers of its constituent atoms, their distribution and the bonds between them. All substances can be represented by a chemical or molecular formula.
In a chemical reaction, two or more reactants are transformed into a number of products as the existing chemical bonds are broken and new ones formed. A bond is a chemical link between atoms. The main types of bonds are covalent and ionic.
Biology is the study of living organisms. Sometimes called the life sciences, biology is concerned with whole populations, single organisms, organs, cells and the biochemical processes that control life.