5 magic science experiments for kids

When Rachel Díaz of Culver City, California, “magically” refilled a soda can for her son, the nine-year-old’s first words were “Cool!” And then: “How’d you do that?”

Science-based magic tricks stand out not just for being fun but for sparking interest in the science that makes the trick happen. “Making science fun is essential to creating the most important aspect of learning: desire,” says Steve Hinkley, president and CEO of the Adventure Science Center in Nashville, Tennessee. “When children find joy in something, they seek more of it.”

Studies show that students in science and math learn best when they participate in the lesson. These simple “magic tricks” help children understand scientific topics by learning how each trick works. Abracadabra … you’ve made fear of science disappear!

Refill an empty can—without any liquid.

You’ll need: 
• Sealed soda can
• Needle or pin
• Drinking glass

What to do: Have kids stand over the sink and pierce the can’s top half with the needle. Drain about half the soda into a glass. Crush the sides of the can until it looks empty.

Tell kids to hold the can with one finger over the hole—then shake. The can will look like it’s “magically” refilling! (Keep that sink handy—it can get messy.) If they’re performing this for an audience, have them pop the top and take a sip.

Cool science: Of course, the can isn’t refilling with soda—but thanks to carbonation, it’s refilling with gas. Carbonation is the process of dissolving carbon dioxide into a liquid. To do this in things like soda, scientists use pressure to dissolve the carbon dioxide and seal the can to keep the pressure in. Popping the top releases the pressure so the gas escapes. But shaking a sealed soda causes the dissolved carbon dioxide to bubble out of the liquid and become gas once again.

Because there’s no place for the gas to go in a sealed can, the carbon dioxide builds up. That’s why soda will explode in your face if it’s shaken before opening. It’s also why—if half the liquid has been drained and a finger is over the hole when the crushed can is shaken—the gas pushes outward on the crumpled sides of the can so it appears to be filling up.

Put an egg inside a bottle—without touching the egg.

You’ll need: 
• Hard-boiled egg (peeled)
• Glass bottle with an opening slightly smaller than the egg
• Long matches or a long lighter
• Candle or strip of thick paper, such as newspaper or construction paper

What to do: Have kids lower the candle or strip of paper into the bottle, then light it for them. They can then place one end of the peeled egg over the mouth of the bottle. When the flame goes out, the egg should slowly slide into the bottle.

Cool science: Kids aren’t pushing the egg into the bottle—instead, it’s being pulled inside thanks to air density. Air is made up of tiny pieces of matter called molecules. When the molecules are farther apart, the air’s density—the amount of matter in a given space—decreases as the air expands. When the molecules are closer together, the air density increases as the air contracts.

When you light the paper, the air molecules inside the bottle warm up and move around, which expands the air and decreases the air’s density. But when the fire goes out, the air suddenly cools—the molecules slow down and move closer together, increasing the density so the air takes up less space. Usually the air outside the bottle would rush in to fill this space—but now the egg is in the way! Instead, the air pressure outside of the bottle pushes the egg into the bottle.

(For a little extra magic, have kids hold the bottle upside down and—with their mouths sealed over the bottle opening—blow. The egg should fly out.)

Push a straw through a potato—no superstrength needed.

You’ll need: 
• A straw (Paper straws won’t work, but plant-based “plastic” straws will.)
• A raw potato (You can still cook it later!)

What to do: Have kids hold the straw in one hand and the potato in the other, and try to pierce the potato. (They might nick the skin—but that’s it.) Now have them move their thumb over the straw’s opening and use the other end to stab the potato. This time, it should sink right in.

(Biodegradable plastic straws can be composted. If you used an actual plastic straw in the name of science, upcycle it into an art project or recycle it by placing it in a container made of the same type of plastic before recycling.)

Cool science: The first time the child stabs the potato, air goes in one end of the straw and out the other. But when the opening is covered with the kid’s thumb, the air is trapped with no place to go. So now as the child drives the straw into the potato, they’re compressing—or squeezing in—the air in the straw. As this happens, the air begins to press outward … making the sides of the straw stronger and firmer. And the farther the straw plunges, the more the air is compressed.

Puncture a bag full of water—without any leaks.

You’ll need: 
• Sealable plastic bag (Perhaps repurpose one you just used.)
• Water
• A really sharp pencil

What to do: Have kids fill the plastic bag with water and seal it. In one motion, firmly poke the pencil into the bag. (Try just one side to start, but if you poke fast enough the pencil should go all the way through without leaks.) See how many pencils kids can add before the bag leaks.

Cool science: Polymers are large molecules made of repeating chains of small, simple chemicals. The polymers in plastic bags are human-made and have been developed to be weak but flexible. Because they’re weak, the polymers separate when the bag is stabbed with the pencil. But because they’re flexible, the polymers quickly form new chains and create a seal around the pencil, preventing water from escaping.

Make an empty can roll—without ever touching it.

You’ll need: 
• Empty soda can
• Blown-up balloon
• A person with hair

What to do: On a smooth surface, have kids place the empty can on its side, then let them rub the balloon through someone’s hair. When they hold the balloon near the can, the can will start to move toward the balloon.

Cool science: Most things emit small electric charges, both positive and negative. Rubbing a balloon across your hair causes tiny, negatively charged particles called electrons to move from your head to the balloon. The metal can is made of particles that have both negative and positive charges. Because negative and positive charges attract each other, when a kid places the negatively charged balloon near the can, it attracts the can’s positively charged particles, called protons. That’s why the can will roll toward the balloon.