In this lesson the students will learn how to classify the materials as mixtures, elements and compounds and identify the properties of each group. Also the concept of separation of mixtures will be introduced to the students. Since barring a few exceptions, almost every element or compound is found naturally in an impure state such as a mixture of two or more substances. Many times the need to separate it into its individual components arises and chemical engineers use separation techniques to do this. Separation applications in the field of chemical engineering are very important. A good example is that of crude oil. Crude oil is a mixture of various hydrocarbons and is valuable in this natural form. Demand is greater, however, for the purified various hydrocarbons such as natural gases, gasoline, diesel, jet fuel, lubricating oils, asphalt, etc.