Give each student a paper cup with baking soda. Give each student an eye dropper with vinegar and have them add the vinegar to the baking soda. Ask the students to explain what happened. Ask your students if they were all able to create the same amount of bubbles and what they think they can do to create more bubbles.
Rinse out their cups and repeat the experiment, but this time pour the vinegar into their cups first. Then, have them add a teaspoon of baking soda. Discuss how many bubbles they were able to create.
Explain to your students that you are now going to use vinegar and baking soda to blow up a balloon. Pour vinegar into the bottle so that about one inch is full. Stretch the balloon and place one tablespoon of baking soda into the balloon.
Stretch the balloon over the mouth of the bottle carefully. Lift the balloon slightly to let the baking soda drop into the bottle. Watch as the balloon inflates from the carbon dioxide. Discuss with your students the reason that they think the balloon blew up. Ask them what they think will happen if they do it again. Repeat the experiment.
Discuss with your students how vinegar and baking soda will always react to each other in the same way. Send home instructions for making Irish Soda Bread, available at the Science for Preschoolers website, so they can practice at home with their parents.