Question

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.

Who is correct?

Reggie, because baking and melting cause bonds to be broken, leading to a chemical change.
Reggie, because objects that are heated always undergo chemical changes.
Charlotte, because melting objects only sometimes cause a chemical change.
Charlotte, because baking causes a chemical change, but melting objects is a non-chemical change.

Answer 1

Charlotte is correct — option 4.

Baking the cookie produces chemical changes (Maillard reactions, protein denaturation/coagulation, new compounds and flavors form — irreversible). Melting and then re‑hardening chocolate is a physical change: it changes state (liquid ↔ solid) and crystal form but the composition stays the same. Heating does not always cause chemical change, and the chocolate coating here undergoes a phase change, not a chemical reaction.