The Magic of Shrinking Cups: A Simple STEM Activity for Curious Toddlers

A Simple STEM Activity with Big WOW Factor

If you’ve ever wanted to add a little science magic to your everyday play, shrinking cups might just be your new favorite toddler-approved experiment. This activity is pure gold—easy setup, minimal mess, and just the right amount of “WOW” factor to keep your little one engaged. Plus, it falls under the category of simple STEM activities, making it a great introduction to science for young kids.

What’s even better? You probably already have everything you need sitting in your kitchen. So, let’s turn ordinary plastic cups into tiny, shrunken masterpieces!

What You’ll Need

1. Plastic cups (clear #6 plastic works best)
2. Colored permanent markers
3. A baking sheet
4. An oven preheated to 350°F

How to Do the Shrinking Cups Activity

1. Set up a space where your toddler can decorate the plastic cups. Hand over the permanent markers and let them go wild with their creativity. This is a great time to talk about colors, patterns, and even simple shapes.
2. Once the cups are decorated, place them upside down on a baking sheet. Make sure they have a little space between them.
3. Preheat your oven to 350°F.
4. Place the baking sheet in the oven and set a timer for about 5 minutes.
5. Watch through the oven window as the cups start to shrink and curl up. This is where the magic happens!
6. Once they’ve fully shrunk (usually around the 5-minute mark), carefully remove them from the oven and let them cool before handling.

The Science Behind It

This activity isn’t just fun—it’s a full-on toddler STEM activity. Here’s why:

• When heated, #6 plastic softens and contracts because of the way its molecules were originally stretched during manufacturing.
• As the plastic warms, it tries to return to its original, smaller form, which is why your decorated cup shrinks into a mini version of itself!

Why This Activity is Great for Toddlers

1. Encourages Exploration – Watching the cups shrink before their eyes sparks curiosity and gets them asking questions.
2. Boosts Creativity – Decorating the cups allows toddlers to express themselves through colors and designs.
3. Hands-on Learning – Rather than just hearing about science, toddlers get to see it in action, making it more memorable.
4. Safe and Simple – This is one of those activities using plastic cups that requires minimal prep and little cleanup, making it a perfect activity at home.

Fun Variations to Try

• Shape Experiment – Cut the cups into different shapes before baking and see how they shrink differently.
• Color Mixing – Have your toddler color a cup with two colors and observe how they blend as the cup shrinks.
• Matching Game – Create a set of matching designs and see if your toddler can find the tiny versions of their cups after they shrink.

More Learning Activities Using Plastic Cups

If this was a hit with your toddler, don’t stop here! Plastic cups are surprisingly versatile when it comes to kids learning activities. Here are four more simple color matching activities and games using plastic cups that we’ll be covering in this series:

1. Pompom Color Match Cups – Draw a plastic cup outline on an index card and add three colored dots using dot markers. Place an empty plastic cup in front of each card and match the colored pompoms to the dots.
2. Cup Towers – Use plastic cups and jumbo craft sticks to build towers. Challenge your child to see how high they can stack them or create different structures.
3. Upper and Lowercase Letter Match Cups – Trace the tops of plastic cups onto brown craft paper and write lowercase letters inside each circle. Write uppercase letters on the bottoms of the cups, then match them to their lowercase pairs.
4. Fizzy Art Cups – Cover the bottom of a shallow tray with baking soda. Fill plastic cups with vinegar and food coloring, then use eye droppers to add the colored vinegar to the baking soda for a fizzing masterpiece.

Final Thoughts

Shrinking cups is one of those rare activities that blends fun, science, and creativity in a way that keeps toddlers entertained while learning. Whether you’re looking for an afternoon boredom buster or an easy way to introduce STEM concepts, this activity checks all the boxes.

So grab some plastic cups, let your toddler unleash their inner scientist, and prepare to be amazed by the magic of shrinking cups!

Plastic Cups

Plastic Cups

Colored Permanent Markers