Chemical or Physical, That is the Question

This is a good basic article that I would insist a chemistry student (or a middle school student as well) read. Not all color changes are equal. When new substances are formed with new prop... See More

This is a good basic article that I would insist a chemistry student (or a middle school student as well) read. Not all color changes are equal. When new substances are formed with new properties such as a change in color [Iron (silvery grey) + oxygen (colorless) = rust (reddish brown)] then we have a chemical reaction. But mixing red paint and yellow paint to make orange paint does not a chemical change make.

Going beyond rules of thumb

Memorizing rules of thumb can often lead to misconceptions such as a color change indicates a chemical reaction; often but not always. In this piece the author looks behind the rule to exami... See More

Memorizing rules of thumb can often lead to misconceptions such as a color change indicates a chemical reaction; often but not always. In this piece the author looks behind the rule to examine why color change may indicate a chemical reaction and when it does not. Use of the phenolphthalein example brings in the added complication of reversible chemical change which may be confusing to beginning students.