Valentine’s Day Science Activity Fizzy Hearts

This Valentine’s Day science activity is the perfect mix of fun and learning! Kids will love creating fizzy heart reactions with this baking soda and vinegar experiment.

A young girl wearing handmade heart-themed paper crown is seated at a table covered in a purple tablecloth. One girl is holding a dropper filled with red liquid over a silicone mold containing heart-shaped baking soda creations. The other girl watches as a pink fizzing reaction spreads across the tray.

The cutest Valentine’s Day science activity for kids

Get ready for a heart-popping good time with this Valentine’s Day science activity!

This hands-on experiment combines simple kitchen ingredients with the magic of fizzing chemical reactions, making it perfect for curious kiddos.

Not only is it an engaging preschool science experiment, but it’s also a great way to spark excitement for Valentine’s Day.

💖 Check out our collection of the BEST Valentine’s Day activities for kids!

Two girls are captured mid-reaction of a Valentine's Day science activity. One girl holds her hands to her cheeks with a surprised expression as she watches the fizzing hearts. Both girls are wearing paper crowns and seated at trays filled with pink and red fizzing liquid.

This Valentine’s Day science activity is perfect for preschoolers

If there’s one thing preschoolers love, it’s baking soda and vinegar experiments.

With just a few minutes of prep, you’ll be setting the stage for bubbly heart-shaped fun.

Kids will love watching the colorful fizz bubble over as they explore this baking soda and vinegar experiment.

It’s science, art, and fun all wrapped into one!

Have you seen these other Valentine’s Day faves?

A close-up of a blue silicone mold filled with dried heart-shaped baking soda pieces for a Valentine's Day science activity. The hearts are sprinkled with red glitter, giving them a sparkly appearance, and some powder is scattered on the white countertop surrounding the mold.

Materials

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Baking soda
Vinegar
Water
Coloring – ex: liquid watercolors or food coloring
Large mixing bowl + spoon or spatula
Heart-shaped silicone molds, muffin tin, or silicone cupcake liners
Eyedroppers or spoons
Glitter – optional
Shallow trays

A close-up shot of a child’s hands using a clear plastic dropper to pick up red liquid from a container. The child is working over a pink tray containing heart-shaped baking soda pieces sprinkled with glitter, while small bubbles of fizzing liquid are visible on the tray.

How to make fizzy hearts with baking soda and vinegar

Mix baking soda with a small amount of water to form a thick paste. Start with a little, adding more as needed.
Scoop the paste into heart-shaped silicone molds (muffin tins or silicone cupcake liners also work great).
Let the hearts dry overnight.
Carefully pop the hearts out of the molds (and don’t worry if some break a little as they’ll still work just fine).
Fill small cups with vinegar and add a few drops of coloring to each. (Tip: Dilute your vinegar with equal parts water to make it stretch even further.)
Provide kids with eyedroppers or spoons and invite them to drip the colored vinegar onto the hearts.
Watch as the hearts fizz and bubble with colorful reactions.

💡 Teacher Tip: Spoons are easier than eyedroppers. We often provide kids with both to set everyone up for success.

Three young children wearing colorful paper heart crowns are seated side by side at a table with purple and pink trays doing a Valentine's Day science activity. They are focused on using spoons and droppers to add red liquid to the heart-shaped baking soda pieces, creating small fizzing reactions in the trays.

How to introduce eyedroppers for this Valentine’s Day science activity

Teaching kids to use eyedroppers is a fun mini-lesson in itself and helps build essential fine motor skills.

Start with a demonstration: Show them how to gently squeeze the bulb of the dropper to push air out. Hold it in front of them and explain that letting go while the tip is in liquid will “magically” suck the liquid up into the dropper.

Next, provide practice time: Give them a small cup of water and an empty container like a muffin tin or ice cube tray. Encourage them to squeeze water from the cup into the empty spaces. This gives them time to practice control and precision in a low-pressure setting.

Last, time to make the hearts fizz!

Three children sit side by side, each focused on their trays. Their paper heart crowns are visible, and they are using spoons and droppers to interact with heart-shaped baking soda pieces. The trays are filled with pink and red fizzing liquid from the reactions.

Exploring bases and acids with this Valentine’s Day science activity

This easy science for kids introduces the basics of chemical reactions.

When baking soda (a base) and vinegar (an acid) mix, they create carbon dioxide gas—that’s the fizzing you see.

We also love actually using the words “base” and “acid” as we play. It’s not only adorable to hear preschoolers use the words while they play, but it’s also a dynamite way of organically growing their science vocabulary.