Lesson Objectives
  • Define a chemical change
  • Explain how a chemical change from a physical change
  • Explain whether chemical changes can be reversed
  • Describe the speed of chemical changes
  • Explain the role of heat and light in chemical changes


Engage: Activate Prior Knowledge; Generate Interest

Show students the video segment Phase Change Experiment .
Write the terms given at the beginning of the clip on the board or chart paper. (condensing, freezing, melting, melting, evaporating)
Ask students if these processes are chemical or physical changes. (all physical changes, phase changes)
Divide students into small groups to discuss what happened to the baking soda and vinegar. Have each group answer the following questions: Are the baking soda and vinegar still present after the balloon blows up? What made the balloon blow up? Is this different than making water vapor by boiling water? Follow this up with a whole-class discussion.


Explore: Allowing Students to Experience Content

Display the following questions for the students. Tell them that they will be doing a series of activities that are focused on answering these questions.

  • What is a chemical change?
  • How is a chemical change different from a physical change?
  • Can chemical changes be reversed?
  • How fast are chemical changes?
  • How is heat involved in chemical changes?
  • How is light involved in chemical changes?

Assign students to complete the Exploration Chemical Changes. (Students should record information on the Student Worksheet.)
Ask students if they can tell if heat/light energy is involved in each change.

chem_changes_ex.jpg keep_dark_ebook.png

Have students complete the reading passages Keep It in the Dark and A Special Day.
You may wish to use a Listen-Read-Discuss strategy to help students understand the reading. First, ask students if they have ever had an infected cut and discuss how hydrogen peroxide is used to kill germs, or bacteria, because a chemical reaction happens. Remind students that a chemical reaction is the same as a chemical change. After you finish your discussion, ask students to read the passage. Then, have them break up into small groups to discuss the reading and to add to their notes about the questions.

Explain: Firm Up Understanding; Allow Students to Explain What They Know

Assign students to watch or show the video segments Slow Chemical Changes in Matter and Fast Chemical Reactions. Tell students that should use the essential question “How fast are chemical changes?” to organize their notes.

Have students review the interactive glossary terms chemical change, chemical reaction. and physical change. Have them use the essential questions to organize their note-taking. After they finish exploring the terms, ask them to use their notes to write answers to the essential questions.

9-12-2011_2-13-59_PM.jpg 9-12-2011_2-12-36_PM.jpg 9-12-2011_2-13-17_PM.jpg

To review the Essential Questions, show students the video segment Chemical Changes (stop at 4:20 minutes).

As a class, develop a list of slow and fast reactions from students’ notes. Discuss how chemical changes may be fast or slow. Ask students to explain what is needed to turn cake batter into a cake (it requires heat). Discuss how heat and light can cause some chemical changes to happen as well as how some chemical changes give off energy as heat or light.

Elaborate: Allow Students to Apply What They Know

Students will complete the Hands-On Activity Heating Up

Project Ideas: To help your students apply their understanding of chemical changes, you may wish to have your students complete some or all of the following projects. The time required to complete each project will vary; some may require students to work outside the classroom.

  • Students can apply their knowledge of chemical changes identifying which common materials undergo chemical changes at normal conditions. For example, some metals rust, but plastics don’t rust. Meat cooks when heat is added, while the pan the meat is in just gets hot but doesn't alter chemically. Why do some materials experience chemical changes and some do not, given the same conditions?
  • Have students make a list of the ingredients used to make a family dinner. Students should make a chart that describes the chemical changes and the physical changes that each ingredient undergoes during the process of cooking. Students should explain how they decided which type of change occurred for each ingredient.

Evaluate: Check for Understanding
Evaluate Activities can occur at any point in the lesson

Have students complete the Brief Constructed Response (BCR) item titled Chemical Changes
Play for the class the video quiz Changes in Matter Ask students for responses to the questions as a review.

9-12-2011_5-03-59_PM.jpg 9-12-2011_4-58-11_PM.jpg