Question

what do these two changes have in common? a penny tarnishing burning a candle select all that apply. both are only physical changes. both are chemical changes. both are caused by heating. both are caused by cooling.

Explanation:

• Chemical change: A penny tarnishing involves a chemical reaction (oxidation) between copper in the penny and substances in the air. Burning a candle is a combustion reaction (a chemical change) where wax reacts with oxygen to form new substances like carbon dioxide and water. So both are chemical changes.
• Cause: Tarnishing can be affected by factors like humidity (not just heating). Burning a candle is a chemical reaction that occurs due to the heat from the flame (initiation of combustion). But cooling is not a cause for either of these changes. Also, they are not just physical changes as new substances are formed in both cases.

Answer:

Both are chemical changes.