A solution is the most common type of a homogeneous mixture comprised of particles that are so small that they cannot even be seen with a microscope.  A solution must have one or more substances dissolved into another substance.  A solution will also never settle to the bottom of its container.  Vinegar and hydrogen peroxide are examples of solutions.

A colloid is a type of mixture with particles that are larger than those in the solution but still too light to settle out.  Fog is an example of a colloid.  Fog has tiny drops of water spread throughout the air.  Detecting colloids can be difficult, but shining a beam of light at a colloid will make the light scatter.  This scattering of light is called the Tyndall effect.  A suspension is a heterogeneous mixture containing a liquid in which visible particles settle.  Italian dressing and chocolate milk are suspensions.

Review:

1. Identify two characteristics of solutions.
2. What is a colloid?
3. Explain the Tyndall effect.