Explain how compounds and mixtures differ.

A mixture can contain any number of elements, whether or not they are bonded together, while a compound is made up of two or more elements bound together.

The two ways that elements are bonded together are covalently (sharing electrons) and ionically (donating electrons). When this electron movement happens, the elements share properties. For instance, when sodium (Na+) and chlorine (Cl-) bond ionically, the extra electron that sodium has in its outermost shell is donated to the chlorine (which is lacking one). Keep in mind that sodium is an extremely reactive, explosive solid and chlorine is a toxic gas. Once a compound is formed (NaCl), it can be used for french fries.

A mixture comprises various elements or materials. It can be homogeneous, meaning the different parts are not visible, or heterogeneous, meaning the individual parts are identifiable. The best mixtures are known as solutions. For example, consider a pitcher of Kool-Aid, which contains water, sugar, and flavoring mix. Because it is homogeneous, the individual parts are not visible. Other homogeneous mixtures include air and ocean water.

A taco salad is one example of a heterogeneous mixture; you can see the lettuce, tomato, chips, and other vegetables all in one bowl. Another example of a heterogeneous mixture is beach sand.

Compounds are formed by chemically combining two or more elements in fixed ratios, while mixtures consist of physically combined substances with variable compositions.