Oxygen when prepared by this method has some color and odor because it is not entirely pure. Pure oxygen has no color, taste, or odor. Oxygen is not a combustible’ substance; that is, oxygen does not burn. But it is a supporter of combustion; that is, many other substances burn readily in oxygen.
Thus, if you light a piece of wood, blow out the flame, and then thrust the wood into oxygen before the burning coal on the wood has gone out, the wood will at once burst into flame. Iron and some other metals will burn in oxygen, also. If you heat the end of a piece of iron picture wire very hot and, while it is still incandescent, thrust it into a jar or bottle of oxygen, it will burn vigorously, giving off dazzling sparks.
Thus the wood and the iron oxidize, that is, they combine with oxygen and form substances that are called oxides. The process by which oxygen combines with some other substance to form a new substance is known as oxidation: Thus the burning of iron or wood is an example of oxidation. .The iron and the wood oxidize, and oxides are formed. When substances oxidize, heat is given off.