Fizzy Frozen Hearts Experiment

This Fizzy Frozen Hearts Experiment is such a hit with the kids! Anytime we can make anything fizz, you know that it’s going to be fun. We’ve done this experiment a zillion times and I foresee it happening a zillion more times in our future, too. Since Valentine’s Day comes around once a year, I always know that we’re going to be doing this fun STEM activity.

Make sure to let the kids get excited for this one. It’s really a lot of fun and one that they can really take charge and do. As long as you’re there to help, let them be the scientist and walk through all the steps.

Looking for more activities like this? Check out these awesome Valentine’s Day Science Activities that kids will love.

fizzy frozen hearts experiment

Speaking of fun science experiments, make sure to check out my Heart Magic Milk Experiment for even more creative Valentine’s Day fun! You can never have too many heart experiments, ever!

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Fizzy Frozen Hearts Experiment

What’s fun about this fizzy hearts experiment is that it’s a great way to teach the kid about reactions. The baking soda paired with the vinegar is what really causes the show! Have the kids talk about what they think is going to happen and then see if they’re right.

In the medical world, this is known as a hypothesis and it’s always so much fun to see what the kids are going to guess.

Having this be heart-shaped really does set this activity up to be great for Valentine’s Day. The kids can easily help make it and have something fun to look forward to that day as well. This would be super fun to do at home, or at a class party, too!

Anytime you can combine fun and learning, that’s a winning combination to have!

Supplies needed to make this Fizzy Heart Experiment

The great thing about this heart experiment is that you just need some simple common supplies to make it! You actually probably already have them sitting around the house.

  • baking soda
  • warm water
  • vinegar
  • food coloring

You’ll also need a heart shaped mold to make the hearts, too. (and don’t worry, if you don’t have a heart-shaped mold, all is not lost. You can still do this experiment with any type of mold that you have in any shape.)

supplies needed for frozen hearts

After you’ve gathered up the supplies, you’re ready to get started. Combine the water with the baking soda and mix it together. It will look kinda of like a sand mixture at that point in time.

combining the baking soda and water

Then let the kids add in the food coloring. A few drops or a lot – whatever they want to do! We choose red because of the heart but this could easily be done in any color.

This is a fun way to make it different and unique each and every time. Let the kids choose different colors and have a blast with it.

adding to the molds

Once the mixture is made, you get to add them to the heart molds and let them harden. We usually put them in the freeze overnight so that they’re good and hard and stay together.

adding the vinegar

The next day, or whenever they’re frozen, remove from the mold and set on a plate or dish. Add the vinegar to the plate and watch the fizzing begin! It’s such a cool site to see!

watching the hearts fizz

As the fizzing is happening, talk to the kids about what they’re seeing and if they’re able to actually just see the fizz or can they hear it as well. You’ll be amazed at how they can see it and hear it and get excited telling you all about it at the same time!

This is the point in the experiment where I tell the kids that they should write down what they’re seeing as well. This is a great way for them to think critically about the experiment and then take turns comparing notes at the end.

fizzy hearts STEM

Want a fun ready to go Valentine’s kit that will delight your kids? Grab one of these craft or play dough kits from Etsy. They’re super adorable and a great way for new play ideas at home!

What are some ways that you can expand or try different options for this fizzy heart experiment?

The options are endless. This is where you can have the kids try different things and see what they can get to work. It doesn’t even mean that it actually has to work, either.

Some ideas are to change up the amount of baking soda used and see if that makes a difference. Will it still fizz or will it fizz out and not work?

Also let them make different shapes and see what happens. Does one type of shape work better than the others at fizzing? Or does the shape even really matter at all?

Another option is to consider the size of the heart or mold that you’re using. Does changing the size make a difference at all?

All of these are fun to think about and can really make the experiment stand out and be different and unique.

adding the vinegar

Fizzy Frozen Hearts Experiment

This fizzy experiment is such a great STEM activity for the kids!


  • ¾ cup baking soda
  • ¼ cup warm water
  • Red food coloring
  • Vinegar
  • Heart-shape silicone mold
  • Shallow bowl


  1. In a large mixing cup, stir together the baking soda and water until the baking soda is dissolved. Stir in red food coloring.
  2. Pour the mixture into the heart-shaped silicone mold and freeze overnight or until completely frozen.
  3. Pour vinegar into the shallow bowl.
  4. Carefully lower the frozen heart into the vinegar.

As you can see, this experiment is just a really fun and unique way to let the kids have some hands-on fun. They’ll feel like a combination between a magician and a scientist and will love every minute.

This would be fun to do as a class experiment with the kids or just a super cool activity at home. I love how simple it is to do and it’s so easy to replicate over and over again.

More Valentine’s Day Activities

Simple Heart Experiments

Looking for a way to incorporate science and Valentine’s Day? Here is a list of simple heart experiments that are Valentine’s Day-themed!

Valentine STEM Activities

If your kids love STEM activities, you must try these Valentine STEM Activities packed with exciting science experiments, slime recipes, engineering a structure challenge, and more!

Candy Heart Science Experiments

Are you looking for a fun activity that involves candy hears or conversation hearts? Look no further than these candy heart Science experiments!

More Fizzy Science Activities

There are so many other fun fizzy experiments to do as well. They’re all a bit the same and a bit different, all at once. Below are a few others that I think the kids will have a blast with as well. You can never have too much fizzy fun!

Fizzy Baking Soda Christmas Tree Experiment

This is perfect to do during the holidays! What a fun way to get some hands on learning during one of the most exciting times of the year!

Fun Fizzy Apple Volcano Science Experiment

Check out this fun volcano science activity! Show the kids and get the supplies ready because they’re going to be geared up for this one!

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