1. Explain to students that a substance is anything that is made up of "stuff" and takes up space. The substance might be in the form of a solid, a liquid, or a gas. Ask students for the definition of a solid, a liquid, and a gas. Ideally, their definitions will be based on their experience comparing and categorizing solids, liquids, and gases. Then point to a desk and ask:

• Is this desk made out of a substance?
• Is it a solid, a liquid, or a gas?

Repeat the questions for a book, a window, tap water, hair, air, and so on. Then ask students to identify additional objects in the room and categorize them as solids, liquids, or gases.

2. Plan to explore a "substance of the day" in your science area. Have "substance investigation tools" available, such as magnifying glasses, scales, droppers, magnets, toothpicks, and cups. Some possible substances to explore might be water, wood, packing peanuts, plastic beads, vegetable oil, rocks, fur, metal objects, a helium balloon, a fan blowing air, and *Oobleck (a slightly messy but really cool mixture of water and cornstarch; see recipe below). Ask students to observe the substances and explore them with the tools. Then have students report their findings to the class. You could also have students compare and contrast substances; for example, a Venn diagram that compares water and Oobleck would be very interesting.

3. Tell students that they are going to watch what happens when different substances are mixed together. (Or supervise students as they mix these substances together themselves.) Begin by mixing water and sand together. Ask:

• When water and sand are mixed together, do they change into something else? (Some students might say that a change has occurred because the mixture looks different from its ingredients.)
• Can this mixture be separated back into its original parts? (yes) How? (The water could be filtered out of the sand, or the mixture, if left alone, will settle into two parts.)

Now ask students to predict what would happen if the following substances were mixed together: plastic beads and vegetable oil; air and water (for example, air blown through a straw into a cup of water); and rocks and packing peanuts. (The substances do not change. They can be easily separated out from the mixture.)

4. Show students the Acids and Bases: Testing Rockets video. Stop the video after the ZOOM cast members tell you about the ingredients. Ask your class if lemon juice, baking soda, and water are all substances. Categorize each one as a solid, liquid, or gas. Then ask students to predict what might happen when lemon juice and baking soda are mixed together.

Tell students that sometimes when two (or more) substances are mixed together, a change occurs and another substance (or substances) is created. This is called a chemical reaction. Gas may form, heat may be produced, and color may change. These types of changes indicate that a chemical reaction has occurred. Also explain that some substances when mixed together produce no chemical reaction.

5. Play the video again, and stop after the first cork pops off of the soda bottle. Ask:

• Has a chemical reaction occurred? (yes)
• What clues tell you that a chemical reaction has occurred?

6. Start the video again, and play it until the ZOOM cast members describe carbon dioxide. Stop the video when they say, "See the bubbles? Carbon dioxide is a gas." Ask:

• How is the carbon dioxide similar to and different from the baking soda and the lemon juice?
• Was the carbon dioxide there before the lemon juice and baking soda were mixed together?
• Where did it come from? (It was produced when the lemon juice and baking soda mixed together; it is a result of a chemical reaction between the lemon juice and baking soda.)
• Why do you think the creation of carbon dioxide made the cork pop off?

7. Watch the rest of the video resource. Ask:

• Was there a chemical reaction when the ZOOM cast mixed orange soda and baking soda? (no)

8. Demonstrate for your class some other chemical reactions. First, spread out newspapers on your work surface, as these experiments can be messy. Then mix one half cup of vinegar and one tablespoon of baking soda together, and watch the chemical reaction that occurs. (If you wish, have students try it themselves.)

Tell students that they just witnessed a chemical reaction -- the vinegar and the baking soda combined to make a new substance. The bubbles they saw forming were filled with carbon dioxide, a byproduct (result) of the chemical reaction. Ask students to predict what will happen when vinegar and powdered laundry detergent are mixed together. Then mix the substances and watch the reaction.

9. Explore other types of chemical changes, as follows:

• Pour one half cup of purple cabbage juice into one quarter cup of lemon juice. The color change you see is a result of a chemical change.
• Have students add other liquids to purple cabbage juice to see whether or not the substances react chemically. In separate cups, have them combine one half cup of purple cabbage juice with one quarter cup of each of the following: vinegar, water, water to which two tablespoons of baking soda have been added, cola, liquid soap, and pickle juice. Some of these substances, when mixed with the cabbage juice, will cause a visible chemical change, and others will not.
• Boiling or frying an egg is also an example of a chemical change. Examine raw and cooked eggs and talk about the change that occurs in an egg when it is cooked. Discuss the idea that sometimes chemical change can take longer than a few seconds to occur. For example, boiling an egg can take 10 minutes.

10. Then demonstrate the sand and water again, but before you do, ask students to predict what will happen. Ask:

• Do you think a chemical reaction will take place?

11. Show students the Acids and Bases: Making a Film Canister Rocket video. Then distribute the Acids and Bases: Making a Film Canister Rocket (PDF) handout and have students make their own. Be sure to have students wear safety glasses and stand back a safe distance when launching their rockets. Ask students to describe to you what is happening. Then ask:

• Why does the film canister separate from its lid and launch into the air like a rocket?