physical. a physical change means that the appearance or state of something changes and no new substances are formed. boiling is the CHANGE OF STATE from liquid to gas. this means that it's a physical change. a chemical change would mean that the kind of substance changes and the result would be a NEW SUBSTANCE FORMED. an example of a chemical change would be an egg frying.
a tip to differentiate between the 2 is that physical changes are often reversible while chemical changes are often irreversible.
good luck!
