9.1 – Composition of Matter
- Elements and compounds are substances; a mixture is composed of two or more substances.
- A solution is a homogenous mixture.  Colloids and suspensions are two kinds of heterogenous mixtures.
- Element: matter composed of only one type of element
- Compound: made from combining atoms of 2 or more elements
- Substance: either an element or a compound
- Mixture: a combination of 2 or more substances that can be separated by physical means
- Heterogeneous mixture: materials can be easily distinguished
- Homogeneous mixture (also called a solution): materials are evenly spread out so you can’t easily see the different elements; ex. sugar dissolved in water
- Colloid: a heterogeneous mixture that stays mixed (substances don’t settle out); appears cloudy 
- Tyndall effect: cloudy appearance of colloids (due to the large size of the dissolved substance)
- Suspension: a heterogeneous mixture where a substance does settle out

9.2 – The Colloid Connection
- Lime and alum form an aluminum hydroxide colloid that is used to help remove finely suspended particles from water supplies.
- Coagulation: small suspended particles are attracted to each other, become larger, and settle out
- Exhaust from some industries may be a soot-containing colloid, which can be coagulated by using electricity in the smokestacks.

9.3 – Describing Matter
- Physical properties are characteristics of materials that you can observe without changing the identities of the substances themselves.
- In physical changes, the identities of materials do not change.  In chemical changes, substances in materials change to different substances.
- Physical properties can be observed without changing the identities of substances; chemical properties indicate chemical changes substances can undergo.
- The law of conservation of mass states that during any chemical change, matter is neither created nor destroyed.