A scientist is performing an experiment on a powder. Which of the following is a sign that a chemical change has definitely occurred during his experiment?
The powder catches on fire.
The powder releases bubbles.
The powder heats up.
The powder breaks apart into smaller particles.
The powder catches fire. The rest of the choices pertains to physical changes on the powder. When the powder catches fire a chemical change happens. For example, if the powder is organic, carbon dioxide and water will result during the combustion.
