I WONDER - What Are The Signs That A Chemical Reaction Is Occurring?

Chemical reactions often provide clues such as color changes, bubble formation, or temperature shifts. An example is mixing food coloring with vinegar and baking soda, which produces bubbles and may change color. Some reactions, like those involving sulfur, can emit distinct smells, such as rotten eggs. These indicators help identify when a chemical reaction is occurring.

Why are bubbles forming considered a sign of a chemical reaction?

What kind of smell might you notice during some sulfur reactions?