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Chocolate Lollipops

In this activity, students will observe the change of state of solid chocolate to liquid chocolate and then observe the liquid chocolate become solid once again.  

As the solid chocolate comes in contact with the hot water, the chocolate absorbs the heat energy and begins to melt. The melting point of chocolate depends on how much cocoa butter is found in the chocolate chips. Then, the melted chocolate is squeezed over a popsicle stick and left to cool until it solidifies.

Objectives

  • Differentiate between the three main states of matter.

  • Understand transitions between states of matter.

  • Describe the properties of a solid and a liquid.

  • Describe the processes of melting and solidification.

Materials

  • Per Student:
    1 popsicle stick
    1 small Ziploc bag
    ½ cup of Chocolate chips
    square of wax paper
    plastic cup of hot water
    Observations sheet
    pencil

Key Questions

  • Can you describe the difference between a solid, liquid or gas?
  • What happens to the solid chocolate when it contacts the hot water?
  • What happens when you leave the melted chocolate out at room temperature?

What To Do

  1. Provide each student with a Ziploc bag containing the chocolate chips.
  2. Reserve 1 bag of chocolate chips to leave at room temperature as an experimental control.
  3. Have students record their initial observations of the chocolate chips. Are they solid, liquid or gas?
  4. Provide each student with a cup of very warm water. (Make sure the water is not too hot to handle.)
  5. Have students place the bag of chocolate chips into the cup of hot water. Have students make observations. What is happening?
  6. After 5-10 minutes, the chocolate should have melted. Have students record their observations at this point.
  7. Give each student a popsicle stick and a square of wax paper. Have students snip a corner off the zip lock bag then squeeze the chocolate through this hole onto the wax paper. Press the popsicle stick into the melted chocolate.
  8. Have students record their observations at this stage of the chocolate phase change.
  9. Let the chocolate set for 25-30 minutes before removing it from the wax paper. The chocolate can also be refrigerated to speed up the solidification process.

Extensions

  • Which chocolate will melt faster? White, milk or dark chocolate? Design an experiment to test out the different types and record your observations.