STEM Penny Challenge: Fun Science and Engineering at Home

Table of Contents

1. Introduction
2. What is the STEM Penny Challenge?
3. Activity 1: Drops on a Penny (The Surface Tension Test)
4. Activity 2: The Penny Boat Challenge (Engineering and Buoyancy)
5. Activity 3: The Penny Bridge (Structural Integrity)
6. Activity 4: Shiny Pennies (Chemistry and Oxidation)
7. Connecting Penny STEM to the Kitchen
8. Why Hands-On Learning Matters
9. How to Structure the Challenge for Different Ages
10. Troubleshooting Common Issues
11. The Role of Failure in STEM
12. Making it a Competition
13. Organizing a "Penny Day" for Educators
14. The Long-Term Benefits of STEM Challenges
15. Conclusion
16. FAQ

Introduction

We have all been there: a rainy afternoon, a living room full of energy, and the sudden realization that the usual toys just are not cutting it anymore. You reach into the couch cushions or the jar on the kitchen counter and find a handful of spare change. What looks like simple pocket change to us can actually be the key to an afternoon of deep learning and excitement for your child.

At I'm the Chef Too!, we believe that the best classrooms are often found in the heart of the home. This article explores the STEM penny challenge, a series of hands-on activities that use a humble copper coin to teach complex concepts like surface tension, buoyancy, and structural engineering. Whether you are a parent looking for screen-free engagement or an educator planning your next classroom unit, these challenges provide the perfect blend of "edutainment."

We will walk through four distinct penny-based activities, the science behind each one, and how you can relate these concepts back to the wonderful world of cooking. By the end of this guide, you will have a full toolkit of low-cost, high-impact STEM adventures ready for your next family activity day.

What is the STEM Penny Challenge?

The phrase STEM penny challenge actually refers to a collection of different activities rather than a single experiment. The common thread is the use of pennies as a primary tool for testing scientific theories or engineering designs. These activities are popular in homes and classrooms because they require almost no specialized equipment.

Most people encounter two main versions: the Drops on a Penny challenge and the Penny Boat challenge. However, the versatility of the penny extends to chemistry and bridge-building as well. Each variation targets a specific branch of STEM (Science, Technology, Engineering, and Math).

For parents, these challenges are a "win" because they use materials you already have. For children, they are fascinating because they yield visual, immediate results. There is something almost magical about watching a dome of water grow on a tiny coin or seeing a flimsy piece of foil support a heavy stack of "treasure."

For another way to explore the same ideas, try these penny STEM challenge activities.

Activity 1: Drops on a Penny (The Surface Tension Test)

This is perhaps the most famous of all the penny experiments. It is a classic physics challenge that explores how water molecules interact with each other and with the surface of the coin.

Materials Needed

To get started, you only need a few items from your kitchen:

• A clean, dry penny (older pennies work just fine)
• A small cup of tap water
• An eyedropper, pipette, or even a plastic straw
• A flat, stable surface
• A paper towel for minor spills

Step-by-Step Instructions

Step 1: Make a prediction. / Before touching the water, ask your child to guess how many drops of water will fit on the surface of the penny. Most kids guess five or ten.

Step 2: Set the stage. / Place the penny flat on a paper towel. Ensure it is perfectly level so the water does not slide off prematurely.

Step 3: Start the drops. / Fill your dropper with water and slowly add one drop at a time to the center of the penny. Count out loud together: one, two, three...

Step 4: Observe the dome. / As you reach 15 or 20 drops, you will notice a large, shimmering dome of water forming on top of the coin. It will look like a glass bead resting on the metal.

Step 5: Reach the breaking point. / Continue adding drops until the water finally breaks its "skin" and spills onto the paper towel. Record the final number.

For more ideas that build on this activity, explore these surface tension experiments for kids.

The Science: Cohesion and Surface Tension

Why does the water stay on the penny instead of running off immediately? The answer lies in cohesion. Water molecules are very attracted to one another. They want to stick together like tiny magnets.

On the surface of the water, the molecules have no other water molecules above them to grab onto. Because of this, they pull extra hard on the molecules next to and below them. This creates a strong "skin" on the surface, which we call surface tension. This tension is what allows the water to bulge into a dome shape.

Key Takeaway: Surface tension acts like an invisible, stretchy skin that holds liquids together until the force of gravity or the weight of the liquid becomes too great for the "skin" to hold.

Taking it Further: The Soap Variable

Once your child has mastered the basic challenge, introduce a variable. A variable is something you change in an experiment to see how it affects the outcome. Add a tiny drop of dish soap to your cup of water and try the experiment again.

You will find that the soapy water spills much faster—often after only five or six drops. This is because soap is a surfactant. It gets in between the water molecules and breaks their "grip," significantly weakening the surface tension.

Activity 2: The Penny Boat Challenge (Engineering and Buoyancy)

While the first challenge was about physics, this one is all about engineering and Archimedes' Principle. The goal is to build a vessel that can hold the most "cargo" (pennies) without sinking.

Materials Needed

• A square sheet of aluminum foil (roughly 6x6 inches)
• A large bowl, sink, or plastic tub filled with water
• A large stash of pennies (you may need 50 or more!)

Step-by-Step Instructions

Step 1: Design the vessel. / Give your child the foil and explain that they can fold it into any shape they want. Should it be a flat raft? A deep canoe? A square box?

Step 2: The float test. / Place the empty foil boat in the water to make sure it floats on its own.

Step 3: Add the cargo. / Carefully place pennies into the boat one at a time. Encourage your child to spread the weight out evenly rather than stacking them all in one spot.

Step 4: Analyze the failure. / When the boat eventually sinks, take it out and look at where the water came in. Was the side too low? Did the bottom rip?

Step 5: Redesign. / Use a fresh piece of foil and try to improve the design based on what you learned in the first round.

The Science: Buoyancy and Displacement

This challenge teaches kids about buoyancy, which is the upward force that keeps things floating. When you place the boat in the water, it pushes water out of the way. This is called displacement.

The water pushes back with an upward force. If the weight of the water being pushed away is equal to the weight of the boat, the boat floats. By making the boat wider or give it higher sides, you displace more water, which creates more upward force to support the heavy pennies.

Bottom line: A boat's ability to carry weight depends on its volume and shape; the more water it displaces, the more weight it can hold.

Activity 3: The Penny Bridge (Structural Integrity)

This challenge moves the focus to civil engineering. It explores how the shape of a material can change its strength. This is a fantastic way to show kids how real-world structures like skyscrapers and bridges are designed.

Materials Needed

• One piece of construction paper or cardstock
• Two sturdy cups or blocks (to act as the bridge supports)
• Pennies

Step-by-Step Instructions

Step 1: The flat bridge. / Place two cups about four inches apart. Lay a flat piece of paper across them. Start placing pennies in the center. Usually, the bridge collapses after just a few coins.

Step 2: Identify the problem. / Talk about why it failed. The paper is "floppy" and cannot resist the downward pull of gravity and the weight of the coins.

Step 3: Change the shape. / Ask your child how they could make the paper "stiffer" without adding more paper. Suggest folding it into an accordion shape (pleats) or folding up the edges to create "girders."

Step 4: Retest. / Place the folded paper back on the cups and add the pennies. A pleated piece of paper can often hold dozens of pennies!

The Science: Weight Distribution

In engineering, the shape of a beam is often more important than the material it is made of. When you fold the paper into an accordion shape, you are creating vertical "walls" that resist bending. This distributes the weight of the pennies across multiple points, making the structure much stronger.

This is the same reason why cardboard has a "wavy" layer in the middle. That wavy layer provides structural support while keeping the material lightweight.

Activity 4: Shiny Pennies (Chemistry and Oxidation)

This challenge is perfect for children who love "magic" tricks that are actually rooted in science. It explores the chemical reactions between metals and acids.

Materials Needed

• Dull, dirty-looking pennies
• White vinegar
• Salt
• A glass bowl
• Paper towels

Step-by-Step Instructions

Step 1: Create the solution. / Mix about a quarter cup of vinegar with a teaspoon of salt in the bowl. Stir until the salt dissolves.

Step 2: The half-dip test. / Hold a dull penny halfway into the liquid for about 20 seconds. Pull it out and observe. The submerged half will be bright and shiny, while the top half remains dull.

Step 3: The full soak. / Drop several pennies into the bowl and let them sit for five minutes.

Step 4: The oxidation experiment. / Take half the pennies out and rinse them thoroughly with water. Take the other half out and place them directly on a paper towel without rinsing.

Step 5: Observe the change. / After an hour, the unrinsed pennies will likely turn a blue-green color.

For a related activity, read this classic penny chemistry experiment.

The Science: Chemical Reactions

Pennies are covered in copper. Over time, that copper reacts with the oxygen in the air to form copper oxide, which is the dull, dark coating you see. The vinegar (an acid) and salt react together to dissolve that copper oxide, leaving the shiny copper underneath.

When you do not rinse the pennies, the remaining copper atoms on the surface react with the oxygen and the chlorine from the salt. This creates a new compound called malachite, which is the same green color you see on the Statue of Liberty!

Connecting Penny STEM to the Kitchen

At I'm the Chef Too!, we love these penny challenges because they use the exact same logic we use in our cooking STEM adventures. The kitchen is essentially a laboratory where physics, chemistry, and engineering happen every single day.

When your child observes surface tension on a penny, they are learning a concept that applies directly to baking. Think about making a glaze for a dessert. The viscosity and surface tension of that glaze determine if it will sit beautifully on top of a treat or run off the sides in a messy puddle.

If your child enjoyed the "Drops on a Penny" challenge, they would likely love our Galaxy Donut Kit. In that adventure, we explore how different liquids and colors interact to create stunning, celestial patterns. Just like the penny challenge, it requires patience, a steady hand, and an understanding of how molecules behave.

Similarly, the chemical reaction used to clean pennies is very similar to the reactions we explore in our Erupting Volcano Cakes kit. While the penny uses vinegar to dissolve oxide, the volcano kit uses specific ingredients to create a bubbling, "lava" reaction. Both teach children that combining two safe, household substances can create a brand-new result.

Finally, the penny bridge challenge is a great introduction to the structural engineering required in baking. Building a multi-layer treat like our Wild Turtle Whoopie Pies requires an understanding of foundations and balance. If the filling is too soft or the "beams" (the cakes) are not positioned correctly, the structure fails—just like a weak penny bridge.

Ready to continue exploring hands-on STEM through cooking? You can join The Chef's Club for a new monthly adventure.

Why Hands-On Learning Matters

You might wonder why we focus so heavily on physical activities like the STEM penny challenge instead of using digital apps or videos. The reason is rooted in how children's brains develop.

Active vs. Passive Learning

When a child watches a video of someone else doing a science experiment, they are a passive observer. Their brain is receiving information, but it is not necessarily processing it deeply. When that same child has to physically squeeze a dropper and count "23, 24, 25," they are engaging their fine motor skills, their focus, and their critical thinking.

The Power of "Edutainment"

The best learning happens when children don't even realize they are "studying." This is the core of our philosophy. By turning a lesson on buoyancy into a game to see whose boat can hold the most pennies, we remove the pressure of the classroom. This builds confidence. A child who feels successful in a penny challenge is more likely to feel brave when they encounter a difficult math problem or a complex science concept in school later on.

Screen-Free Bonding

In a world of tablets and televisions, these challenges provide a rare opportunity for families to gather around the kitchen table. It is a time for parents to ask "What if?" and "Why do you think that happened?" These open-ended questions are the foundation of the scientific method.

For more simple, screen-free ideas, explore these easy STEM activities for kids at home.

How to Structure the Challenge for Different Ages

The great thing about the STEM penny challenge is that it is "scalable." You can make it simpler for a preschooler or more complex for a middle-schooler.

For Preschoolers (Ages 3-5)

Focus on observation and counting.

• Practice fine motor skills by using the dropper.
• Count the drops out loud together to build number fluency.
• Talk about colors and shapes (the round penny, the clear water).
• Focus on the "wow" factor of the water dome.

For Early Elementary (Ages 6-8)

Focus on predictions and simple variables.

• Have them write down their hypothesis (guess) before starting.
• Introduce the soapy water variable.
• Let them lead the boat design process.
• Encourage them to draw what they see at different stages.

For Older Kids (Ages 9-12)

Focus on data collection and engineering design.

• Perform multiple trials (do the test three times) and find the average number of drops.
• Try different types of coins (nickels, dimes, quarters) and compare the results based on surface area.
• In the boat challenge, give them a "budget" (e.g., they can only use 4 inches of tape or a certain amount of foil).
• Discuss more complex terms like displacement, density, and oxidation.

Troubleshooting Common Issues

Even simple experiments can sometimes go wrong. If your penny challenge isn't working as expected, check these common factors:

• The Penny is Dirty: If there is oil or grease on the penny (from fingers or pockets), it will break the surface tension early. Wash the penny with dish soap and dry it thoroughly before starting the "Drops on a Penny" challenge.
• The Surface is Tilted: If your table is even slightly slanted, the water dome will pull to one side and spill much sooner. Use a level or find the flattest spot in your home.
• Dropping too Fast: If you "squirt" the water rather than letting it fall as a single drop, the force of the stream will break the surface tension. Encourage your child to go slowly—one... Mississippi... two... Mississippi...
• Foil is Ripped: In the boat challenge, even a tiny pinhole will sink the vessel. Make sure to handle the foil gently as you fold it.

The Role of Failure in STEM

One of the most important lessons a child can learn from a STEM penny challenge is that it is okay to fail. In fact, failure is a necessary part of the scientific process.

If the boat sinks immediately, don't rush to fix it for them. Instead, ask, "Where did the water come in?" or "What do you think we should change for the next version?" This teaches resilience. It shifts the focus from "getting the right answer" to "solving the problem."

In the kitchen, we see this all the time. Maybe the first batch of cookies is a little too flat, or the cake doesn't rise quite as much as we hoped. We don't give up; we look at the recipe, check our measurements, and try again. This iterative process—the cycle of testing, failing, and improving—is exactly how the world's greatest inventions were created.

For more hands-on inspiration, explore these no-prep STEM activities for home and school.

Making it a Competition

If you have multiple children or are working in a classroom setting, you can easily turn these challenges into a friendly competition.

• The "Heavy Hauler" Award: For the boat that holds the most pennies.
• The "Steady Hand" Award: For the person who gets the highest number of drops on their penny.
• The "Structural Master" Award: For the bridge that supports the most weight relative to its size.
• The "Best Design" Award: For the boat or bridge that looks the most creative while still being functional.

Competition can be a great motivator, but remember to keep the focus on the learning. After the winner is announced, have them explain why they think their design worked so well. This allows the whole group to learn from the successful model.

Organizing a "Penny Day" for Educators

If you are a teacher or a homeschool co-op leader, a "Penny STEM Day" is an excellent way to cover multiple curriculum standards in one afternoon.

Lesson Plan Idea

1. Morning Session: Start with the "Shiny Penny" chemistry activity. While the pennies are soaking, discuss the history of the penny and the properties of copper.
2. Mid-Day Session: Move to the physics of "Drops on a Penny." Use this to introduce the concept of molecules and attraction. Have students graph their results on a whiteboard to see the class average.
3. Afternoon Session: End with the "Penny Boat" or "Penny Bridge" engineering challenge. This allows kids to use their built-up energy in a constructive, creative way.

Our school and group programmes are designed to support this kind of thematic learning. We know that when educators have access to structured, hands-on activities that blend science and art, student engagement sky-rockets. Whether you use food-based kits or simple household items like pennies, the goal is the same: making education an adventure.

The Long-Term Benefits of STEM Challenges

Engaging in these activities regularly does more than just fill an afternoon. It helps develop a "STEM mindset." Over time, children who participate in hands-on challenges like these start to look at the world differently.

They don't just see a bridge; they see the triangles and arches that give it strength. They don't just see a boiling pot of water; they wonder about the molecules turning into steam. This curiosity is the engine of lifelong learning.

By starting with something as small as a penny, you are showing your child that they have the power to investigate, experiment, and understand the world around them. You are building their critical thinking skills and their ability to tackle complex problems with a calm, methodical approach.

Conclusion

The STEM penny challenge is a perfect example of how the most profound lessons often come in the simplest packages. From the shimmering dome of a water drop to the structural strength of a paper bridge, these activities prove that science isn't just something that happens in a lab—it happens on our kitchen tables, in our sinks, and even in our pockets.

At I'm the Chef Too!, we are dedicated to helping families discover these "aha!" moments through the joy of edutainment. Whether you are exploring the physics of fluids with our Chef's Club subscription or testing the limits of a foil boat, the goal is always to spark curiosity and create memories that last long after the pennies are put back in the jar.

• Gather your pennies and a few kitchen supplies.
• Choose one of the four challenges to start with today.
• Encourage your child to ask "Why?" and "What if?" at every step.
• Celebrate the failures as much as the successes!

"The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' but 'That's funny...'"

Ready to take your hands-on learning to the next level? Explore our collection of individual kits and join a community of families who believe that learning should always be delicious and fun.

FAQ

How many drops of water can a penny actually hold?

While most people guess around 5 to 10 drops, a clean penny can often hold between 20 and 30 drops of plain tap water. Some people have even recorded up to 40 drops by using a very steady hand and a perfectly level surface. The exact number depends on the cleanliness of the coin and the size of the drops.

Why does dish soap make the water spill off the penny faster?

Dish soap is a surfactant, which means it reduces the surface tension of the water. It gets between the water molecules and interferes with their ability to "cling" to one another. Without that strong surface tension, the water cannot form a tall dome and will spill over the edge much sooner.

What is the best shape for a penny boat?

In the foil boat challenge, a wide, flat-bottomed boat with high sides usually performs the best. This shape displaces a larger volume of water, which creates more buoyancy (upward force) to support the weight of the pennies. Spreading the pennies out across the bottom of the boat also helps maintain stability.

Can I use other coins for these STEM challenges?

Yes, you can! Using different coins like nickels, dimes, or quarters is a great way to extend the learning. Ask your child to predict if a larger coin (like a quarter) will hold more or fewer drops than a penny, and then test it to see if surface area or the "lip" of the coin makes a difference.