* Elements are pure substances made up of only one type of atom (e.g., sodium, carbon, oxygen).

* Compounds are formed when two or more elements chemically combine in a fixed ratio (e.g., sodium carbonate, Na₂CO₃).

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

Sodium carbonate solution is a mixture of sodium carbonate (Na₂CO₃) dissolved in water (H₂O). The sodium carbonate and water retain their individual properties within the solution, and they can be separated by evaporation.