The physical changes among the options you provided are:
- melting chocolate: This is a physical change because it involves a change in state from solid to liquid without altering the chemical composition of the chocolate.
- cutting wood: This is also a physical change because it does not change the chemical structure of the wood; it simply alters its shape and size.
The other options involve chemical changes:
- burning butter: This is a chemical change because it involves a reaction that alters the chemical composition of the butter.
- souring milk: This is also a chemical change as it involves the fermentation process that changes the chemical composition of the milk.
So, the correct answers are melting chocolate and cutting wood.