If we view a science as a body of systematized knowledge, then chemistry is usually called a natural science because it 【C1】______ knowledge of the natural world. At times we may wonder 【C2】______ there is no complete system 【C3】______ all of chemistry fits perfectly. Gaps in the present system, however, show that chemistry is still a(n) 【C4】______ subject and that we 【C5】______ all of its facts, laws, and theories. 【C6】______ , chemistry as a science is very much 【C7】______ us today, and its future holds the bright promise 【C8】______ much more to come. Man's knowledge about himself and nature has grown into 【C9】______ sciences. The growth of the separate sciences has been more developmental than intentional. The separation of the natural sciences into physical and biological sciences, and physical sciences into physics and chemistry, happily 【C10】______ a larger body of knowledge into more manageable parts. At the same time we should remember that the concepts, techniques, and applications of the various sciences are interdependent and not exclusively a part of one science or 【C11】______ . In this 【C12】______ , chemistry is a key science among the natural sciences because everyone, 【C13】______ the area of natural science he wishes to pursue, needs at least an introduction to the principles and simpler applications of chemistry as a foundation for his specialty. Chemistry deals with the 【C14】______ of matter, changes in matter, the laws and principles 【C15】______ these changes, and the concepts and theories that interpret them. 【C1】