Materials:

• 1/2 pint of heavy cream
• 1 clean pint jar or other similarly-sized container with a tight cover or lid, preferably plastic
• 1 clean marble

Instructions:

• Take your jar and place the marble inside
• Pour the cream into the jar and screw the cover on tightly
• Have the children shake the jar. A figure-eight motion seems to work best, but let your kids go wild (not so much, if the jar is glass). If you have a plastic container with a tight lid, you can even roll it back and forth.
• Listen for the marble bouncing up and down.
• After the marble cannot be heard anymore, you’ll know the cream is thickening. Keep shaking, and you will soon start to see the glob of butter form.
  The marble will go silent as it is enveloped by the butter.
• Find and remove the marble
• Place the butter into a container of your choice to store or use.

The end result: a delicious scoop of butter!

What is this science magic that has just unfolded before your eyes?
Heavy cream is what is called an “emulsion”. An emulsion exists when tiny droplets of one type of liquid are floating around in another type of liquid that does not like to mix with the first. In the case of heavy cream, tiny globules of fat are suspended in mostly water. By shaking the heavy cream in the jar, you are forcing the fat globules to slam into one another. If they hit each other with enough force, they will simply stick together, the fat collection becoming bigger and bigger with each extra globule. After enough shaking, the fat globules form a chunk of butter.

To take this experiment even further, have your students try different types of cream, such as light cream or whipping cream; each of which has different fat content. They can compare the shaking time needed, the amount of butter created, and the butter’s taste at the end.

This experiment is definitely a workout and will require a good amount of shaking, so, if you have students that are smaller or have short attention spans, think of using two smaller containers (and a marble in each one) to speed up the process.