* Physical Changes: These changes alter the form or appearance of a substance but don't change its chemical composition. The substance remains the same, just in a different state.

* Chemical Changes: These changes result in the formation of new substances with different chemical properties.

Examples of Mixture Formation (Physical Changes):

* Salt and Water: When you mix salt and water, the salt dissolves, but it doesn't chemically change. You can evaporate the water and recover the salt.

* Sand and Water: You can easily separate the sand and water, demonstrating that no new substance was formed.

* Air: Air is a mixture of gases like nitrogen, oxygen, and carbon dioxide. Each gas retains its individual properties.

Key Point: In mixtures, the components retain their original properties. You can usually separate them by physical means (like filtration, evaporation, or magnetism).