Classification of Matter

Mixture
Two or more elements or compounds that are blended together without combining chemically.
Heterogeneous mixture
A mixture that is not the same throughout with visible particles that can be separated from the mixture.
Suspension
Heterogeneous mixture in which particles can be seen, particles will settle out eventually. Light shining through a suspension will show the suspension's particles (Tyndall effect).
Homogeneous mixture
A mixture that is well-mixed with no visible boundaries, with identical properties throughout.
Solution
An extremely well-mixed homogeneous mixture in which one substance (solute) is dissolved uniformly in another (solvent). Light shining through a solution will not show any particles.
Alloys
A solid solution, usually of metals.
Colloids
Non-separating mixture with particle sizes between solutions and suspensions. Light shining through a colloid will reflect off of the colloid particles.
Elements
The simplest pure substance, composed of just one kind of atom.
Compounds
A pure substance made of two or more elements that are chemically combined. The compound will have different physical and chemical properties than the parent elements. The elements always combine in the same ratio or proportions.
Molecules
The smallest particle of a compound that retains the properties of the compound. Consists of two or more elements chemically bonded together.

There are several types of colloids:

Name Composition Example
Aerosol Liquid in gas Fog
Aerosol Solid in gas Smoke
Foam Gas in liquid Whipped Cream
Solid Foam Gas in solid Marshmallow
Emulsion Liquid in liquid Milk
Solid Emulsion (gel) Liquid in solid Butter
Sol Solid in liquid Paint, cell fluid
Solid Sol Solid in solid Ruby