* Elements are the simplest pure substances and cannot be broken down into simpler substances by any means.

* Compounds are formed when two or more different elements combine chemically in a fixed ratio. They can only be broken down into their constituent elements through chemical reactions.

* Mixtures are combinations of two or more substances that are not chemically bonded. They can be separated by physical means like filtration, evaporation, or distillation.

Examples:

* Water (H₂O) is a compound made of hydrogen and oxygen. It can only be broken down into these elements by electrolysis (a chemical process).

* Salt (NaCl) is a compound made of sodium and chlorine. It can be decomposed into its elements through electrolysis.

* Air is a mixture of gases like nitrogen, oxygen, and carbon dioxide. These gases can be separated by physical means like fractional distillation.