t's Peggy Sue's birthday and she's about to blow out the candles on her cake. Brother Roger stops the party when he shouts: "Look at that! Chemical and physical changes taking places on your birthday cake!" How would you respond to Roger? A) Roger is incorrect. The melting wax is a physical change but there is no chemical change taking place. B) Roger is correct. Lighting the match is a chemical change and burning the candles is a physical change. C) Roger is correct. The melting wax is a physical change and the burning candle wick is a chemical change. D) Roger is incorrect. Only a chemical change is taking place as evidenced by the light and heat of the burning candles.

D) Roger is incorrect. Only a chemical change is taking place as evidenced by the light and heat of the burning candles.

Explanation:

- A physical change is a change in which there is no formation of new substances. Examples of physical changes are the melting or the evaporation of a substance (all phase transitions are examples of physical changes) : in such cases, there is no formation of new substances.

- A chemical change is a change in which new substances form. Examples of chemical changes are the chemical reactions: for instance, when a candle burns, a reaction is taken place (oxygen is burnt, transforming into carbon dioxide + heat + light, so this is an example of chemical change).

Therefore, the correct answer is

D) Roger is incorrect. Only a chemical change is taking place as evidenced by the light and heat of the burning candles.