What kid doesn’t LOVE searching for magic hidden treasure? Add frothy, foamy, colorful bubbles and this science activity for kids is irresistible!

What kid doesn’t love hunting for hidden treasure? Add a colorful fizzy chemical reaction on top of the hunt and you have an activity that will keep the kids entertained all afternoon.

It was love at first sight when I came across these exploding treasure chests from Fun-A-Day and these magic treasure rocks from Growing a Jeweled Rose. Inspired by these fun activities, I came up with our own summer-themed magic hidden treasure molds.

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Magic Hidden Treasure Molds

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Wax Paper

Baking Sheet

Cookie Cutters

Baking Soda


Liquid Water Colors

Plastic Treasures (We bought our plastic jewels from the Dollar Store. You could also use plastic beads or coins!)


Liquid Dish Soap

Plastic Pipettes

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To make hidden treasure molds:

  • Place wax paper on a flat baking sheet. Place cookie cutters on top of the wax paper.
  • Mix up a 2:1 paste of baking soda to water. We used about 2 cups of baking soda and 1 cup of water, which made 6 molds.
  • Use liquid water colors to dye the paste. A little bit of color always makes the activity more fun!
  • Fill each cookie cutter mold about halfway with paste. Place some plastic “hidden treasures” inside and then fill the cookie cutter mold up the rest of the way so you can’t see any treasures. It is normal for some of the water to leak out the bottom of the cookie cutter. Don’t worry!
  • Place the baking sheet in the freezer overnight.
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Let the magic begin:

  • Pull each cookie cutter mold off the wax paper and break off any frozen water that leaked out. Place it in a bin, bowl, dish, or on a plate.
  • Pour some vinegar into a cup and add a squirt of dish soap. Stir to mix.
  • Use a plastic pipette to squirt the magic hidden treasure mold with the vinegar mixture. Watch as it fizzes, foams, and melts!
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  • Gather the hidden treasures as they appear. Have fun!
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*Our molds didn’t slide out from the cookie cutters easily at first. We waited for them to melt a little bit before they came out of the cookie cutters.

What Causes the Fizzing?

As you may have guessed already, the “magic” in magic hidden treasure molds is caused by the chemical reaction between baking soda and vinegar. When this base and acid react they produce carbon dioxide gas, which are the fun bubbles you see. The liquid dish soap makes the bubbles more frothy. It also makes the reaction go slower and last longer.

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Another one of our favorite fizzy reactions also changes colors! Check out the magic color changing chemical reaction and be sure to subscribe to our monthly newsletter below for updates on more fun science activities for kids!

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