Elements - Elements are substances that are made up of only one type of atom. The symbols shown on the periodic table represent the known elements. Elements are made up of smaller particles, but they are not broken down by ordinary chemical means. Compounds - Compounds are substances that are made up of more than one type of atom. Water, for example, is made up of hydrogen and oxygen atoms.
Carbon dioxide is made up of carbon and oxygen atoms.
Table salt is made up of sodium and chlorine. Compounds can b decomposed, or broken down by simple chemical reactions. Phase - A phase is any region of a material that has its own set of properties. In a chocolate chip cookie, the dough and the chips have different properties, therefore they represent separate phases. Pure gold, which is an element, would only contain one phase.