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An element is a substance made up of one type of atom.
A compound is a substance that is formed when two or more elements chemically join.
A mixture is when two or more substances are mixed together but are not chemically joined.
Very few substances in nature are found on their own – they are usually mixed with other substances. Many foods for example, are mixtures of many substances. Just look at this food label from a box of breakfast cereal:
Some examples of mixtures include:
Oil and water
Soil
Breakfast cereals
Salt and sand
Iron and sulfur
A mixture contains two or more substances which are just mixed together and not chemically joined with each other.
In a mixture the elements retain their physical and chemical identity and separating mixtures does not involve a chemical reaction.
The video below shows the difference between a mixture of iron and sulfur and the compound iron sulfide where the two elements are chemically joined together.
Dissolving – is not a chemical reaction
You know that sugar is a solid and that it dissolves in water if you stir it well.
Sugar is said to be soluble in the water.
Water is said to be the solvent for sugar.
The sugar is called the solute.
This forms a solution – a mixture of sugar and water.
This is not a chemical reaction
The video below shows the solubility of some common substances and illustrates how you know whether or not a substance is soluble.
A dilute solution is one in which there is a relatively small amount of solute dissolved in the solution.
A concentrated solution contains a relatively large amount of solute.
A saturated solution is a solution in which no more solute can be dissolved in the solvent.
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