2.3: Evidence That Change Has Occurred

Each fall, we see the leaves change colour and then fall to the ground. This annual event is evidence that a chemical change has occurred. Some environmental changes occur because of human interference, while others are a natural progression of life. 

While reading the paragraph from page 31, think of two other examples of chemical change that occurs in nature.

1. Describe a chemical change that occurs in nature. What is the evidence that a chemical change has occurred?

2. What evidence of a chemical change is shown in the pictures? 

After watching the segments on Investigating Chemical Reactions and after reading "Evidence of Chemical Change" on page 34, respond to the questions below.

3. List five pieces of evidence that show that a chemical change has occurred.

4. Give an example where a colour change is the evidence of the reaction.

5. Give an example where bubbles appear during the reaction.

6. What do you call the solid that forms as a result of combining two chemicals?