Here's why:

* Mixtures can be combinations of different compounds. For example, saltwater is a mixture of sodium chloride (a compound) and water (a compound). Air is a mixture of nitrogen, oxygen, carbon dioxide, and other gases.

* Mixtures can also be combinations of elements and compounds. For instance, a mixture of iron filings and sulfur is a mixture of an element (iron) and a compound (sulfur).

* Mixtures can be different states of matter. You can have a mixture of solids (like sand and salt), a mixture of liquids (like oil and water), a mixture of gases (like air), or a mixture of different states (like salt dissolved in water).

Key takeaway: Mixtures are combinations of substances that are not chemically bonded together. These substances can be elements, compounds, or different states of matter.