Introduction то chemistry

Chemistry is an experimental and theoretical study of the composition of matter and the changes that take place in matter. A chemical change involves changes in composition and in properties. A physical change involves only changes in properties with no change in composition.

Chemical changes are usually accompanied by the liberation or the absorption of energy in the form of light, heat or electricity.

All forms of matter consist of either pure substances or mixtures of two or more pure substances. Elements are the building blocks of matter. Compounds are combinations of elements. Most of the elements are metals and most of them will unite with other elements and form compounds. The formation of a compound from simpler substances is known as synthesis. Analysis is the process of breaking down a compound into simpler substances or its elements and thus is the determination of its composition. The composition of a pure substance never changes.

Every substance has physical and chemical properties. Physical properties include colour, smell, solubility, density, hardness and boiling and melting points. Chemical properties include the behavior with other materials.

Matter exists in three states: the solid, the liquid and the gaseous state. A substance (usually) can be transformed from one state to another under the changes of its temperature.

Chemistry is so much a part of our lives that it is very easily taken for granted. Metals, glass, plastics, dyes, drugs, insecticides, paints, paper, soaps, detergents, explosives and perfumes are all made of chemicals.