Stop Chocolate Melting – STEM Challenge

If you love chocolate this is the STEM challenge for you! All you need is a bar of chocolate, a warm sunny day and some bubble wrap, kitchen foil and black or white paper.

The challenge is to find a way to package a chocolate bar so it doesn’t melt in the sun.

This activity would also be fantastic for a school science club!

You’ll need

3 small chocolate bars or one large bar split into 3 equal pieces

3 small plates


Test materials

  • Black and white paper/card
  • Kitchen foil
  • Bubble wrap
  • anything else you want to try


Place one chocolate bar on each plate

Plate 1

This is the control sample. Leave the chocolate uncovered.

Plate 2

Wrap or cover this sample in one or two of the test materials.

Plate 3

Choose different test materials to wrap or cover this sample.

Leave all three plates in the same place outdoors. All three samples should be in the sunshine not the shade.

Time how long it takes the control chocolate to melt enough that it is soft all the way through. You can test this by pushing a wooden skewer or fork into the chocolate.

Things to think about

The bubble wrap should insulate the chocolate from the heat of the sun as the tiny pockets of air trap the heat. Bubble wrap is a good insulator.

White reflects heat, so the white paper should help keep the chocolate cool. If you wrap a bar of chocolate in black paper, the paper will absorb the heat, warming the chocolate up.

Extension tasks – chocolate melting investigation

Experiment with placing chocolate in different places to see where it the melts fastest on a hot day. Leave the chocolate in its original wrapper and place one indoors not in the sun and two other bars somewhere else, perhaps a fridge, or a pocket. Check the chocolate every 10 minutes to see how squishy it is.

If you have a chocolate bar that has melted, reverse the process by placing in a fridge. Observe how the shape, texture and colour of the chocolate has changed.

More chocolate experiments

Learn about changes of state with these minty chocolate leaves!

Add some chocolate to the marshmallows in a solar oven!

Or try one of my other easy summer STEM challenges.

Science concepts



A great science activity for:

Key stage 2 science ( 7-11 years )

School science club

Homeschool science

Last Updated on July 28, 2022 by Emma Vanstone

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