reaction 2: vinegar and baking soda.

The reaction between vinegar (acetic acid) and baking soda (sodium bicarbonate) is a chemical reaction. You can identify it as a chemical reaction based on the following observations:

1. **Formation of New Substances**: When vinegar and baking soda are combined, they undergo a reaction that produces new substances, including carbon dioxide gas (which creates the bubbles and foam), water, and sodium acetate. The presence of new substances indicates a chemical change.

2. **Gas Production**: The bubbling and foaming you observe is due to the release of carbon dioxide gas. This gas production is a hallmark of a chemical reaction.

3. **Energy Change**: In this reaction, energy is absorbed in the form of heat, which can sometimes be felt as a cooling effect during the reaction. Such energy changes further indicate a chemical process.

4. **Irreversibility**: Chemical reactions often produce products that cannot easily be converted back into the original reactants. In this case, while you could theoretically separate the components under certain conditions, they typically cannot revert to vinegar and baking soda as they originally were in the same way.

These characteristics collectively indicate that the interaction between vinegar and baking soda is a chemical reaction.