The substance changes to a new substance is a chemical change because matter changes its identity, it means that the answer is C.
The original substance can be recovered is a chemical change since the substance changes its identity but it can be recovered to its original identity, it means that the answer is C.
The color changes is a physical change because color is a property of matter, if it changes, the matter still has the same identity, it means that the answer is P.
Gas is produced and given off is a chemical change because gas is normally produced from a reaction, which is a chemical change. It means that the answer is C.
The substance changes size, shape or volume, similar to the third one, the change in the properties does not affect the identity of a substance, it means that the answer is P.