Frozen Fizzy Hearts: A Fun Valentine’s Day STEM Activity

I love baking soda and vinegar activities. They’re the perfect blend of fun, science, and sensory play for preschoolers… and they’re so easy! So when looking for Valentine’s Day STEM activities, these frozen fizzy hearts are an absolute winner, as far as I’m concerned.

Pinterest pin for Frozen Fizzy Hearts: a Valentine's Day STEM Activity

If you haven’t tried baking soda and vinegar fizzy play with your preschooler before, you are missing out. You can click here to read about how this baking soda and vinegar sensory play activity absolutely SAVED me a few years ago when I was 8 months pregnant, everyone in my house had COVID, and we were all on the verge of losing our minds!

And what better way to update a tried-and-true favorite activity than to put a festive seasonal twist on it? These frozen fizzy hearts are perfect for Valentine’s Day, and they’re a great STEM activity, too!

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Materials Needed

To make your frozen fizzy hearts, you’ll need:

Baking soda (about 1 cup)
Vinegar
Food coloring (red, pink, or any desired colors)
Heart-shaped molds (I used a muffin tin like this one)
Small squirt bottles or droppers
Water
Mixing bowl and spoon

Preparation

heart shaped muffin tin with pink baking soda mixture

Make the Baking Soda Mixture: Combine baking soda, water, and a few drops of food coloring in a mixing bowl until it forms a thick paste. I used approximately 1 cup of baking soda to a ¼ cup of water.
Fill the Molds: Spoon the mixture into heart-shaped molds and smooth the surface.
Freeze: Place the molds in the freezer for several hours or until the hearts are solid.

The Fizzy Experiment

child playing with baking soda fizzy hearts (Valentine's Day STEM activity)

Set Up:
- Pop the frozen hearts of your mold. I used a metal muffin tin, so I needed to run the bottom of the tin under warm water to be able to pop the hearts out.
- Place the frozen hearts on a tray or in a shallow dish. I used a big metal roasting pan – shallow enough for easy play, but it had high enough sides to contain the mess!
- Fill squirt bottles with vinegar. (Peri bottles work great for this – IYKYK ?)
The Fun Begins:
- Encourage kids to squirt vinegar onto the hearts and observe the fizzing reaction.
- Provide toys for imaginative play. This is my favorite way to extend this kind of activity. A dinosaur, a unicorn, and a Paw Patrol pup joined in on our fizzy fun.
- Discuss what’s happening: the chemical reaction between baking soda (a base) and vinegar (an acid).

Learning Opportunities

You can make this activity totally educational… or not. It’s up to you! If you do want to make this a full-on science lesson, you can…

Explain the science behind the reaction in simple terms: Baking soda and vinegar react because they are like two “opposites” that get very excited when they meet! Baking soda is a powder that acts like a base, and vinegar is a liquid that acts like an acid. When they mix, they create lots of bubbles because they are making a gas called carbon dioxide. It’s like a fizzy surprise party! The bubbles you see are the gas escaping into the air, and that’s what makes it so much fun to play with!
Discuss sensory exploration: texture, temperature, colors, and sounds.
Incorporate math by counting hearts or timing reactions.

Tips for Success

young girl observing fizzy heart STEM activity

Use a tray and a towel on the floor to contain the mess. A roasting pan like this one was perfect.
Adjust the intensity of the reaction with the amount of vinegar used. I like to have plenty of vinegar on hand so that we don’t have to cut play short if we run out.
Add glitter or small toys inside the hearts for extra fun! I’ll definitely try this next time we do this fun Valentine’s Day STEM activity.

Variations

Try different shapes or colors for other themes. You could easily modify this activity for any holiday or occasion with a different mold (or even cookie cutters) – red and green fizzy Christmas trees would be so fun!
Experiment with scented vinegar or essential oils for added sensory experience. I haven’t tried this, so if you do, I would love to hear about it!
You could also use this activity as a segue to talk about emotions (heart = feelings).

I hope your little ones enjoy this Valentine’s Day STEM activity as much as we did! And if you’re looking for more fun and easy STEM activities, be sure to check these out:

Snag your free guide to sensory play!

Want to incorporate more sensory play into your day, but not sure where to start? I’ve created this FREE guide just for you!

If you try this Valentine’s Day STEM activity, I would LOVE to hear about it! Comment below or tag me on Instagram to tell me all about it!