Monster Exploding Bag Experiment

Activities & Days Out / 20 October, 2020 / Nanny Anita

Monster Exploding Bag Experiment

I love how there seems to be a limitless number of things that you can do with bicarbonate of soda and vinegar. So far we have only used it in two activities (frozen fizzing shapes and volcanoes), but there are plenty more out there like this monster exploding bag experiment. This STEM activity can be done at any time of the year, but I thought it seemed just right for Halloween. It is very easy to decorate a zip lock bag as a monster and get it to explode.

Make sure you follow my STEM board on Pinterest for more ideas, and don’t forget to pin the picture at the bottom.

You will need:

  • Zip lock bag*
  • Vinegar
  • Bicarbonate of soda
  • Tissue/ kitchen roll
  • Pens

* Don’t use a zip lock bag that has a zip as it will let the gas escape.

EC, YC and her friend were very keen to have a go at this, I think the idea of something exploding really appealed to them.


First of all decorate the bag.  YC and her friend made theirs into colourful monsters.


Next fill a tissue with bicarbonate of soda and fold it into a package. We used this part to predict what would happen if we added more or less of the bicarb. Everyone agreed it would be better to add more. Each time we did this experiment we added one more spoonful to our packages.

Pour some vinegar into the zip lock bag.  This is another thing that you can adjust the amount of.

Finally comes the tricky part, you have to get the parcel into the zip lock bag and seal it quickly.

If the bag is sealed correctly it should start to inflate until it bursts.


Everyone enjoyed watching the bags explode and then anticipating when and how it would burst.  EC decided that he needed to take cover inside the house.  I can assure you the explosion won’t be that big!  You may want to stand at the opposite side to the opening though (just in case).

The Science Behind It

Bicarb of soda is a base while the vinegar is an acid. When added together they create carbonic acid, which is instantly broken down into water and carbon dioxide. As a result the gas gets trapped inside the bag causing it to expand.  When it finally gets too big the bag will “explode”, as a side note there are no big bangs.

Pin for later:

exploding bag experiment. A STEM activity that children are sure to enjoy.


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