Which of the following is a physical change? burning a piece of wood rust forming on an iron fence sawing a piece of wood in half a copper roof changing color from orange to green

Sawing the piece of wood in half is a physical change,
because no new substances are formed that weren't there
before the sawing.

Burning wood produces carbon monoxide and carbon dioxide
that weren't there before the burning.  That's a chemical change.

Rust forming on iron is iron oxide that wasn't there before the
rusting.  That's a chemical change.

The green that appears on copper is copper oxide that wasn't
there before the green appeared.  That's a chemical change. 

It's have to be 12 or idk

The correct answer is  "c".  it is "c" because melting is an endothermic change, and endothermic get's energy from surroundings.