Final answer:
Gas bubbles forming when baking powder and vinegar mix is a chemical change that produces carbon dioxide, salt, and water. The reaction neutralizes the pH of the solution.
Step-by-step explanation:
Gas bubbles forming when baking powder is placed in vinegar is an example of a chemical change. This reaction occurs because baking powder contains sodium bicarbonate (bicarbonate of soda) and a solid acid. When these ingredients come into contact with vinegar, which is an acidic solution, they react to produce carbon dioxide (CO2), salt, and water. The formation of carbon dioxide gas is what causes the bubbling and fizzing you observe. As for the pH of the solution after mixing, since an acid (vinegar) has reacted with a base (bicarbonate from baking powder), the resulting mixture will typically have a pH closer to neutral than the original acidic pH of the vinegar.