* Mixture: A combination of two or more substances that are not chemically bonded. Each substance retains its own properties.

* Pure Substance: A single substance with a fixed composition and properties.

Salt water is a mixture because:

* Salt (NaCl) and water (H₂O) are separate substances.

* They are not chemically bonded. You can separate salt and water through evaporation.

* The properties of salt and water are still present in the mixture. For example, salt water tastes salty and is a liquid.

Let me know if you have any other questions!