You may improve this article, discuss the issue on the talk page, or create a new article, as appropriate. (January 2015) The history of economic thought deals with different thinkers and theories in the subject that became political economy and economics, from the ancient world to the present day. It encompasses many disparate schools of economic thought.
A pure substance is a substance that cannot be separated by physical means. eg. filtration, evaporation, distillation or chromatography. Examples of pure substances include water, gold, glucose, carbon dioxide, oxygen and hydrogen. A pure substance is made up of one type of particle. The particle that makes up water is H 2 O. The particle that makes up carbon dioxide is CO 2.
A mixture of two or more phases of a pure substance is still a pure substance as long as the chemical composition of all phases is the same. Phases of a Pure Substance A pure substance may exist in different phases. There are three principal phases solid, liquid, and gas.. Bahrami ENSC 388 (F09) Properties of Pure Substances 1 Properties of Pure Substances Pure Substance A substance that has a fixed chemical composition throughout is called a pure substance such as water, air, and nitrogen.