Expanding Snowman

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To learn about chemical reactions


Zip lock plastic bags
Permanent marker
Alka seltzer



Use a permanent marker to draw a snowman face on a zipper storage bag. Fill the bag up with snow to make your snowman baggie.

Place 2-3 Alka-Seltzer tablets in the snow-filled baggie. Zip it up tight and then wait to see what happens!

Over the next 30-60 minutes watch as the snowman baggie expands bigger and bigger! You may want to even set it in a larger bowl in case the baggie pops or leaks.

Alka-Seltzer is made of citric acid and sodium bicarbonate (baking soda), which is a base. When the tablets are dry, the acid and base powders don’t mix, but as soon as they are immersed in water they mix and react to form carbon dioxide gas.

It is actually the same chemical reaction that happens when you mix baking soda and vinegar together. An acid plus a base mix to form carbon dioxide gas, which are the bubbles you see. That carbon dioxide gas fills up the sealed baggie and may even make it pop open as the pressure increases!

You’ll notice that it takes a long time for the snowman baggies to inflate. Why do you think this is? What do you think would happen if you filled the baggies with hot water instead of snow? Try it! Let the kids experiment with snow science by varying the temperature of the water and adding more or less Alka-Seltzer. If you are feeling especially adventurous you could even use baking soda and vinegar to make the baggie explode!


  • snow; science; reactions

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