"Paper Burning"
Paper burning is a chemical change because when you burn paper, a new chemical substance, ash, is being formed. These changes are irreversable.
Ash cannot return back to paper state.
Salt dissolving is a physical change. This is because no chemical reaction occurs.
Water boiling is also a physical change. Just like mentioned above, no chemical reaction or chemical substance is being formed. Water turns into a gaseous state, which is reversable (according to the water cycle, a whole different chapter.)