"There must be some kind of chemical change in the rock at that temperature and pressure."

We are discussing the differences between physical and chemical changes right now.

But if it changes color that is evidence of a chemical change.

They add, "The fact that a chemical change is small does not eliminate the risk."

It does give off heat, so there is evidence of chemical change.

This is a substance that changes color in response to a chemical change.

Sometimes chemical changes are able to bring energy into the system.

Rain also can make a chemical change in some rocks.

In the case of burning, there is a chemical change.

A chemical change took place, and lucky for us it did.