Many of the resources on the Earth are impure. They need to be refined are purified so that we have a stock of raw materials which have a constant set of properties. These raw materials are used to make steel, cement, and other items which we use in various industries. Imagine buying a car if the quality of steel could not be guaranteed or going over the Golden gate bridge knowing the steel used was second rate. It is important therefore to purify materials.

Substances can be separated from one another because of differences in the physical properties of the components of the mixture.

• A property is anything about matter that helps identify it.
• The physical properties of a substance are those identifying characteristics that can be OBSERVED or MEASURED without changing that substance. ie. no new substances are formed.