If you’re looking for a simple kids’ science experiment with a BIG wow factor, you’ve come to the right spot!  This science experiment uses just a couple of ingredients, takes just moments to complete and has a super exciting finish.

Make some magic inflating conversation hearts just in time for Valentine’s Day and then hop over to snag more science experiments kids will love!

Getting Ready

To prep this magic kids’ science experiment, I grabbed my supplies:

  • An empty bottle
  • 4 Alka Seltzer tablets for each round
  • 1/2 cup water for each round
  • A couple balloons
  • A Sharpie

Big Brother helped me break two of the Alka Seltzer tablets into small pieces and dropped them into the bottom of the bottle.

Valentine's Day science for kids.

Then, we brainstormed a couple of our favorite conversation heart messages and I used the Sharpie to draw them on the balloons.

Fun Valentine's Day science for kids.

TIP: After a little experimenting, I realized that the conversation heart was more crisp and clear if I first blew it up with air, temporarily pinched it closed with my fingers and then drew the picture.

When I tried drawing the conversation heart while it was flat and empty, the image stretched too much when the balloon inflated.

The Science Experiment

After making a prediction about what was going to happen, Big Brother carefully poured the water into the bottle.

Then, I speedily stretched the mouth of the balloon with my fingers and stretched it over the rim of the bottle.

We eagerly watched the kids’ science experiment happen!  Or was it magic!?

Super simple and fun science experiment for kids. Magic Inflating Conversation Hearts!

We repeated the science experiment over and over again until our pack of Alka Seltzer tablets was empty.

The Science Behind It

Similar to the reaction that occurs when you mix baking soda and vinegar, when you pour water on Alka Seltzer tablets, carbon dioxide gas bubbles begin forming.

These gas bubbles rise up in the bottle, filling the balloon with carbon dioxide gas.

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  2. This was an amazing experiment! I did it with a small group of children for 4-H. Thank you

    We even tried it with sparkling water and baking soda, and another time with vinegar and baking soda. Your experiment here worked better and faster.

    1. Hooray Valerie! I am so glad that you found an experiment that worked!
      Stay STEM-inspired!

  3. I’ve done this with vinegar & baking soda, putting the baking soda in the balloon & then twisting it so I could put it on the bottle.

    I bet you could put the broken pieces of Alka Selzer in the ballon, twist it, attach it to the bottle, & then untwist to let the pieces drop.

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