Exploratorium
Exploratorium: Black Magic
A great and easy-to-do activity where students separate the colors in a black marker and develop an understanding that black is a composite of other colors.
University Corporation for Atmospheric Research
Ucar: About Rainbows
This site from the University Corporation of Atmospheric Research provides an illustrated article about the phenomenon of rainbows.
Frostburg State University
General Chemistry Online: Ten Signs of Chemical Change
Resource provides the ten signs that tell when a chemical change has occured. Each sign has a detailed explanation.