* Elements: Elements are pure substances that cannot be broken down into simpler substances by chemical means (e.g., gold, oxygen, carbon).

* Compounds: Compounds are formed when two or more elements chemically combine in a fixed ratio (e.g., water (H₂O), salt (NaCl)).

* Mixtures: Mixtures are combinations of two or more substances where each substance retains its own properties and can be separated by physical means (e.g., sand and water, salt and water).

Salt water is a mixture because:

* It contains two distinct substances: salt (NaCl) and water (H₂O).

* The salt and water retain their individual properties within the mixture.

* You can separate the salt and water by physical means, such as evaporation.