Reggie and Charlotte are baking oatmeal cookies. They dip the baked cookies in melted chocolate. The chocolate cools to form a hardened coating. Reggie argues the entire chocolate-covered cookie has undergone a chemical change. Charlotte disagrees, saying only the original oatmeal cookie has undergone a chemical change, not the chocolate coating.
Answer
A
Reggie, because baking and melting cause bonds to be broken, leading to a chemical change.
B
Reggie, because objects that are heated always undergo chemical changes.
C
Charlotte, because melting objects only sometimes cause a chemical change.
D
Charlotte, because baking causes a chemical change, but melting objects is a non-chemical change.
Explanation
Baking changes the ingredients in the oatmeal cookie through chemical reactions, so the cookie undergoes a chemical change. Melting the chocolate and letting it harden again are physical changes: the chocolate changes state, but its substance remains chocolate. Therefore, Charlotte is correct that the coating does not undergo a chemical change.
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