Students should learn the differences between elements, mixtures and compounds in order to have thorough knowledge of and be able to recognize compounds. Explain that an element consists of only one type of atom and cannot be broken down into simpler materials. A mixture can be made from molecules of elements and compounds by simply mixing them together, without a chemical reaction, and can be easily separated using techniques such as distillation, chromatography, evaporation and filtration. Give them examples of elements and mixtures. When students have grasped the concept of elements and mixtures, explain to them that compounds are chemicals made by chemically bonding atoms of different elements.
Direct students to conduct an experiment on the reaction between iron and sulfur to make iron sulfide. Fill a test tube with a mixture of iron and sulfur and heat using a Bunsen burner. The mixture should change color and form a compound called iron sulfur. Get students to compare the properties of each element separately in a table, before comparing it with the properties of the compound formed so that they can see the compound has different properties to the individual elements. Explain to students that compounds can only be formed when the atoms in each element are chemically joined together by bonds.
Giving students the chance to separate a common compound, such as water, into separate elements in the classroom is a fun method for teaching students the concept of compound separation. Through an interactive experiment, students will learn that because compounds are formed in a chemical reaction, the only way they can be separated is by another chemical reaction. Electrolysis is an exciting experiment that uses electricity to separate water into its individual elements, hydrogen and oxygen. Explain to students that other separation methods that do not involve chemical reactions, such as filtration and evaporation, can only be used to separate mixtures and cannot separate compounds.
Teaching students about polymers helps them to comprehend the concept and properties of a compound. Explain to students that a polymer is formed from long, repeating chains of the same molecule group and provides an interesting example of a chemical compound. Have students discuss the characteristics of both naturally occurring polymers and polymers that are man-made and why these characteristics make them useful for everyday items, such as plastic bottles and chewing gum. Consider conducting a polymer experiment by adding borax to a natural polymer, the latex in PVA, to make form cross links that will make the glue into a stronger compound.