Solutions and Other Mixtures_ongrade-02

When some chemical elements are mixed, they make compounds. For example, when hydrogen gas and oxygen gas combine, they form new chemical bonds. This creates an entirely new substance: water (H20). Even though water is made of two different elements, it is a pure substance. A glass of water contains only water molecules. If you add something else to the water like sand, you now have a mixture.

Not all matter will chemically combine when mixed. Some gases like nitrogen, oxygen, and carbon dioxide will not form new bonds when placed together. Instead these gases make a mixture called air.

Air is not a compound. Air is not a molecule because the groups of atoms are not joined together. Instead, they are just randomly intermixed. Many common substances, such as wet sand, are mixtures. Wet sand is made of sand and water that do not chemically combine. The trail mix in your lunch bag is also a mixture. In a mixture, properties of the individual substances are not changed.


Some mixtures are heterogeneous, which means that the components of the mixture do not look uniform. Let’s look at a salad. This salad is a combination of lettuce, tomatoes, onion, olives, cucumbers, and cheese. It is not uniform in appearance. If you took a spoonful of this salad, it would not have equal amounts of each salad ingredient in the same proportions. In fact, each time you took a different spoonful, it would be slightly different from all the others. The first spoonful might not have any olives, and another spoonful might not have any cheese. No matter how much you stir the salad, the individual ingredients of the salad are not changed.

They will never chemically combine with one another. Because of this, heterogeneous mixtures are generally easy to separate because the ingredients are usually large in size (can be seen with your eyes).