You can conduct this experiment while students observe or allow students to participate.
- block chocolate broken into chunks (1 chunk per student)
- marshmallows (3-4 per student)
- sauce pan
- hot plate
- wax paper
- Have students observe the properties of the chocolate and the marshmallows. What is the texture? Hardness? Is it solid, liquid, or gas?
- Place the pieces of chocolate into a saucepan; place the saucepan on a hot plate; turn on the hotplate.
- Discuss what you notice happening to the chocolate.
- Add the marshmallows to the chocolate.
- After a few seconds, use a spoon to carefully scoop out blobs of the mixture and drop them onto wax paper.
- Watch the mixture cool and observe the changes to the mixture as it cools.
- Explain that this process is similar to what happens when a volcano becomes active: the solid earth is exposed to extreme heat and changes from solids into liquids. As it cools the liquid (molten lava) transforms into solid rock.
A great wrap up for this experiment students can eat their lavachocolate-marshmallow rocks!
Source: Lisa Siegman. Instructor. New York: Nov/Dec 1998. Vol. 108, Iss. 4; pg. 20, 1 pgs