How to tell whether it’s a physical or chemical change?

 Check for indications that a chemical change has taken place. The following are indications of a chemical change:

• Gas is created. Bubbles can occur in liquids.
• An odour is created.
• The colour of the substance changes.
• Sound is generated.
• There is a shift in the temperature. The environment either heats up or cools down.
• Light is generated.
• A precipitate develops.
• Reversing the change is difficult or impossible.