Imagine a dinner that begins with a salad and dressing, rolls with butter and jam, and cranberry juice. The main course is steak and a baked potato. For dessert, there's strawberry shortcake with whipped cream and coffee.

There are many ways to think of this dinner. You could simply divide the meal into the appetizers, main course and dessert. Or you could categorize the foods based on their protein, carbohydrate, fat and mineral content. This division is more complex, since the foods may fall into more than one category. (For example, the steak contains protein, minerals and fat, as well as water.)

Another method is to divide the food according to how particles are dispersed in it: in other words, how solids, liquids and gases are suspended, or dissolved, in other solids, liquids, and gases. For example, cranberry juice is a liquid that contains insoluble solids (fibers) and dissolved solids (sugars). Jam is also a liquid with a solid (sugar) dissolved in it. However, this liquid is suspended in pectin, which is an insoluble solid.

These dispersions are further classified as true solutions, colloids and suspensions. These classifications form the foundation of this course.

For more information, click on the 3 States of Matter button located in the left-hand column or click on Continue.