In this topic you will learn about how mixtures form and how they can be separated.

Stirring together sand, salt, and iron filings will produce a mixture. A mixture is made if two or more parts are blended together, yet each part keeps its own properties, and does not turn into a new substance. When iron filings and yellow sulfur are stirred together to make a mixture, the iron remains magnetic. You could use a magnet to remove the iron filings.

Compounds are produced by chemical combination of substances. A compound has different properties from the substances it contains. Iron and sulfur combine chemically to make the compound iron disulfide. A magnet will not remove the iron. Unlike iron, iron disulfide is not magnetic.

You can use the physical properties of materials to separate them from a mixture. For example, to separate a mixture of sand and wood chips, first pour in water and stir briefly. The wood chips float to the top. The sand settles to the bottom. The wood chips can be skimmed off and dried. The water can be poured off and the sand dried.

Some mixtures are solutions. A solution is a mixture in which substances are completely blended so that the properties are the same throughout and the substances stay blended. Because alcohol boils at a lower temperature than water, a solution of alcohol and water could be separated by heating them in a special apparatus.

A suspension is a mixture of substances that separate upon standing. A mixture of clay and water is a suspension. A mixture like this can settle into layers.

Some mixtures are emulsions. In an emulsion, a liquid spreads through another liquid. In an aerosol, liquid drops or solid particles spread through a gas.

Many food products are colloids. Gelatin desert is a gel. A gel is a solid spread through a liquid. The solid in gelatin is protein. The liquid in gelatin is water. Whipped cream is a foam. A foam is gas spread through a liquid. The gas in whipped cream is air. The liquid in whipped cream is water and fat.