1. Mixtures and Compounds

2. Composition of Matter One way we classify matter is either pure substances or mixtures. Pure substances are either elements or compounds. An element is a substance that cannot be broken down into simpler substances even by a chemical reaction. A compound is a pure substance composed of two or more elements combined chemically in definite proportions.

3. Elements versus Compounds Identify each of the following as an element or a compound. 1) He 2) H 2 O 3) Sodium chloride 4) copper

4. Mixtures A mixture is a combination of two or more elements or compounds. Mixtures differ from pure compounds in that their components can be separated by physical processes. Examples: * pencil lead * salt water * air

5. Types of Mixtures Homogeneous mixtures have the same composition throughout. Examples: salt water, air, brass Heterogeneous mixtures do not have the same composition throughout. Examples: lake water, soil

6. Solutions A solution is one type of matter dissolved in a liquid or gas. It is a mixture that is completely uniform throughout (homogeneous). Examples: Salt water Sugar water

7. Suspensions Suspensions are heterogeneous mixtures. The different pieces can be mixed together, but they will eventually settle out. Examples: Muddy water Oil and vinegar salad dressings Liquid antibiotics

8. Colloids Colloids are mixtures that are similar to both solutions and suspensions. The particles will not separate, but the particles are visible in the mixture. They can be seen when a light is shown onto the mixture. Examples: Milk Fog Whipped cream