Melt your heart

With Valentine’s day celebrating those we love, here’s an investigation to melt your heart!

You will need

  • Different types of chocolate (dark, milk or white)
  • A small sandwich bag or cling film
  • Your hand


  1. Test 3 different types of chocolate (different makes or types) which are roughly all the same size.
  2. Place each chunk inside a separate piece of cling film or a small plastic bag.
  3. Wrap your hand around the first bag containing a chocolate chunk.
  4. Time how long it takes for the chocolate to begin to melt.
  5. Can you hold the chocolate long enough for it to completely melt?
  6. How long did this take?
  7. Test the next piece of chocolate.
  8. When you have tested all 3 see if you can notice a difference in the time taken to melt the chocolate.


  • What happened to the chocolate 30 minutes after you stopped holding it?
  • Was there a difference between the 3 types of chocolate?


This is a great experiment to demonstrate how melting and freezing are reversible processes.

Melting is a process where something changes state from a solid to a liquid. It is the opposite of freezing and happens when, in this case, the chocolate gains energy from our warm hands. As the chocolate molecules gain energy they begin to move around and spread out from each other more. This makes the chocolate runnier. After a while when the chocolate is away from your warm hands it loses this energy and begins to freeze or solidify.

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