Melting, boiling, and bending are considered physical changes, but burning is a chemical change. explain why this is so.

So, when you make something boiling or melting, its still the same substance. Water doesn't change into something else, just change its state of matter. When you burn something, one substance reacts with another. For example, when you burn carbon in oxygen, you get carbon dioxide. That's the difference.

The correct answer is "atomic weight".