http://www.ck12.org Chapter 3. Chemical Interactions
Introduction
Yummy! S’mores are on the way! Did you ever toast marshmallows over a campfire? The sweet treats singe on the
outside and melt on the inside. Both the fire and the toasted marshmallows are evidence of chemical changes. In
the process of burning, the wood changes to ashes and gases, and the outside of the marshmallow turns brown and
crispy. Neither the wood nor the marshmallows can change back to their original form. That’s because burning is a
chemical change and chemical changes are often impossible to undo. In this unit, you’ll learn about many types of
chemical changes, including how they occur and why you can’t live without them.