Explanation: Chemical reactions occur when two or more substances interact with each other to form new substances. In this demonstration, we will be combining vinegar (acetic acid) and baking soda (sodium bicarbonate) to produce carbon dioxide gas, which will cause a bubbling reaction.

Materials needed: - Vinegar - Baking soda - Measuring spoons - Clear plastic bottle - Balloon

Safety precautions: - Wear safety goggles to protect your eyes from any splashes. - Perform the demonstration in a well-ventilated area to avoid inhaling any fumes. - Do not ingest any of the chemicals used in the demonstration. - Keep a fire extinguisher or a bowl of water nearby in case of any accidents.

Step-by-step guide: 1. Measure out 1 tablespoon of baking soda and pour it into the clear plastic bottle. 2. Measure out 1/4 cup of vinegar and pour it into the bottle with the baking soda. 3. Quickly stretch the opening of the balloon over the mouth of the bottle, making sure it is securely sealed. 4. Observe as the baking soda and vinegar react to produce carbon dioxide gas, causing the balloon to inflate. 5. Discuss with the students the chemical reaction that took place, emphasizing the formation of carbon dioxide gas as a product of the reaction. 6. Allow the balloon to fully inflate before removing it from the bottle and tying it off. 7. Dispose of the used materials properly and wash your hands thoroughly after the demonstration.

Key principles: - The reaction between vinegar (acetic acid) and baking soda (sodium bicarbonate) produces carbon dioxide gas, which causes the balloon to inflate. - This is an example of a chemical reaction where new substances are formed as a result of the interaction between the reactants.

By following these steps and safety precautions, you can safely demonstrate a simple chemical reaction for high school students.