You can physically combine two or more substances into a mixture. These parts keep their own propertieswithout forming new substances. In a solution the properties are the same throughout and the substances stay blended. Combinations of substances that separate upon standing are called suspensions. A gas spread through a liquid is a foam. After a chemical reaction the compound formed has different properties from the substances it contains. Alcohol can be separated from water by heating the mixture. You can use a magnet to separate iron filings from other materials.