Do a Balloon Sandbag Science Experiment

What You Need:

  • Funnel
  • Sand
  • Balloon
  • Water


What You Do:

  1. Give your child a non-inflated balloon and a funnel that fits in the balloon’s opening. Have them put the funnel into the balloon’s neck.
  2. Help them pour sand into the balloon. DRY sand must be used. Even with dry sand, it can take a while to get the sand into the balloon. A toothpick or stick to poke the sand through the funnel may help the process go faster. Fill the balloon almost (but not all the way) full with sand.
  3. Ask your child how the balloon feels with sand in it. Notice that it feels hard, like a rock.
  4. Now have your child fill the rest of the balloon slowly with water through the funnel. Just pour in enough water to cover the sand. You may have to squeeze the balloon to release air first.
  5. Remove the balloon neck from the funnel. Squeeze the balloon again to release air. Help your child tie a knot in the end of the balloon.
  6. Now let them see how the balloon feels with water and sand. Notice the different, softer feel the balloon now has! It is now malleable; your child can knead it, play with it, and make it into shapes!

Help your child understand that sand is made of tiny rock crystals, so at first it felt hard like a rock in the balloon. Water softened the sand crystals. Wet sand is a plastic, a material that can be molded. Wet sand can be formed into shapes whether in or outside a balloon (for example when making sandcastles at the beach!).

Did You Know?

A substance that makes a non-plastic into a plastic is called a plasticizer. In this experiment, water was a plasticizer that made the sand flexible.

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