* Elements: These are the simplest pure substances and cannot be broken down further by chemical or physical means. Examples include gold (Au), oxygen (O), and carbon (C).

* Compounds: These are formed when two or more elements chemically combine in a fixed ratio. The elements in a compound are held together by chemical bonds.

* Physical means like filtration, distillation, or evaporation can only separate mixtures, where components are not chemically bonded.

* Chemical means like electrolysis or chemical reactions are needed to break the bonds in a compound and separate its constituent elements.

Examples:

* Water (H₂O) is a compound made of hydrogen and oxygen. You can't separate water into hydrogen and oxygen just by boiling it. You need electrolysis.

* Salt (NaCl) is a compound of sodium and chlorine. You can't simply dissolve salt in water and then filter out the sodium and chlorine. You need a chemical reaction to break down the compound.