Module 1.3 Physical and Chemical Properties Quiz

Example 4

Label each of the following changes as a physical or chemical change. Give evidence to support your answer.

1. Boiling water
2. A nail rusting
3. A green solution and colorless solution are mixed. The resulting mixture is a solution with a pale green color.
4. Two colorless solutions are mixed. The resulting mixture has a yellow precipitate.

Solution

1. Physical: boiling and melting are physical changes. When water boils no bonds are broken or formed. The change could be written: H2O(l)→H2O(g)H2O(l)→H2O(g)
2. Chemical: The dark grey nail changes color to form an orange flaky substance (the rust); this must be a chemical change. Color changes indicate chemical change. The following reaction occurs: Fe+O2→Fe2O3Fe+O2→Fe2O3
3. Physical: because none of the properties changed, this is a physical change. The green mixture is still green and the colorless solution is still colorless. They have just been spread together. No color change occurred or other evidence of chemical change.
4. Chemical: the formation of a precipitate and the color change from colorless to yellow indicate a chemical change.