Chemistry in the Environment
Chemistry has been definced as the science that is concerned with the composition, properties, and structure of matter and with the ways in which substances can change from one form to another. But this definition is too broad to be useful. Chemistry isn't the only science that deals with the composition and transformations of matter. Matter in the environment is composed of clouds, whose transformations into rain snow are studied by meteorologists; it is composed of lakes studied by limnologists, or of trees which transform by processes studied by forresters. Chemists are unique because they understand or explain everything, even the subjects studied by all the scientists mentioned above, in terms of the properties of just over 100 kinds of atoms found in all matter, and the amazing variety of molecules that are created by forming and breaking bonds between atoms. So chemistry is defined by its approach, not its subject matter. Chemistry explains or understands any subject in terms of the properties of atoms and molecules.Exactly what we mean by a “chemical” needs to be explored, because environmentalists are often opposed to using "chemical" fertilizers, or "chemical" approaches to solving problems. If chemistry explains things in terms of atomic or molecular properties, a chemical must be something that is understood that way. In other words, we might call a glass of water
want to explain the incredible reactivity of water, producing in this case hydrogen which mayexplode. So laypeople who talk of “chemical free” natural foods, for example, are not necessarily at odds with chemists who claim “everything is made of chemicals”. When people speak of "chemical free" products, they usually mean that the material is found in nature and so did not require chemical knowledge to design or understand it. The very same molecule might be called a chemical under some circumstances. Chemists often say 'everything is a chemical" because it is possible to understand everything in terms of molecular properties, but of course anyone who pays attention to common language knows that that is not a meaningful thing to say. Very dangerous "chemicals" are made by natural processes (the strongest poisons known, and by understanding their molecular properties, chemists can learn how to control or destroy them. For example, aflatoxins .
A chemical is generally a pure substance, comprised of just one kind of molecule (or atom), because the properties and behavior of the pure substance can be understood in terms of the properties of that molecule. But molecules identical to those found in all of nature can be synthesized in a laboratory, and they are identical in all respects to natural ones.