What is Chemistry?
Human beings have always been fascinated by natural materials such as wood, water, air and have investigated their transformations. One example of a transformation is burning, also called combustion, where a substance burns reacting with oxygen in the air. Another example is the rusting, where the metal iron reacts with oxygen and water in the air to form iron oxide, a red coloured material.
Although there are many millions of materials around us, during the 19th and 20th centuries, it became clear that all these substances are constructed from just 83 different elements. Some of these elements are metals such as iron (Fe) or copper (Cu) or aluminium (Al) or and some are non-metals such as carbon (C) or phosphorus (P) or the gases hydrogen (H), oxygen (O) or chlorine (Cl). Chemistry is the study of these different elements and how they combine to form compounds such as water (H2O) or salt (sodium chloride - NaCl).
In addition to the 83 naturally-occurring elements, another 27 new elements have been created in the laboratory, bringing the total to 110, known at the present time.