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Root Beer Float Investigations

by Diann Gano, M.Ed

“Can we make a concoction today?” asks Malhar, one of our budding scientists.

It’s a hot Thursday afternoon and everyone is a little shagged from the heat—including me. A concoction sounds like a messy, energy-sapping endeavor, but Malhar is insistent.

“Do you have any root beer?” he whispers to me after looking around to make sure the other children are out of earshot. “And maybe some ice cream?”

Oh Malhar, my little rock star of the kitchen science lab. I’m pretty sure that he had me at “ice cream.” The thought of a science lesson and a cool, refreshing snack all rolled into one jolts me out of my mid-afternoon malaise. Suddenly the prospect of gathering the tools for our scientific investigation—cups, spoons, ice cream and root beer—doesn’t seem like a chore at all.

Malhar sees the smile cross my face. I barely manage to make an affirmative nod before he darts off to gather the supplies for our root beer investigation.

”I’ll get the spoons,” he yells. “You get the other supplies!”

We’ve been on a bit of a roll with our “States of Matter” projects this summer. In the heat and the sun, we’ve been melting crayons, chocolate chips on pretzels and ice cubes by the handful.

Melting solids into liquid is a great way to teach our young scientists about the solid and liquid states of matter. After observing a reaction between a liquid and a solid that releases a gas, the children will conclude their investigation with a cold, sweet treat.

What a great way to indulge in some “edible science” on a ninety-degree day!

After we’ve gathered our materials, Malhar begins to rattle off his science facts as I fill the cups with ice cream. 

“Root beer is a liquid,” he states. “When you add ice cream (which is the solid part) into the root beer, the ice cream reacts with the root beer and releases gas bubbles. It creates a bubbly foam that rises to the top of your cup. And it is DE-licious! The root beer helps to free air bubbles trapped in the ice cream. The fat in the ice cream coats the bubbles, protecting them and allowing them to expand to create the foam you see on root beer floats.”

The children are spellbound by Malhar’s description of this reaction between a liquid and a solid. His fascination with science and his depth of scientific knowledge often light up our days.

As Malhar winds up his mini-lecture, he notices the ice-cream-filled cups and commands me to stop.

“Wait!” he yells. I freeze mid-scoop. “You are doing it wrong! You have to put the root beer in first!

“I do? Really?” I ask. Six pairs of eyes glare at me as if I’m about to sabotage their edible experiment.

I trust most facts that fly out of Malhar’s mouth, and I begin to question myself. Is there a correct way to make a root beer float?  Have I been doing it this way for the past 30 years because it’s the most efficient method for a lone teacher with a passel of preschoolers? On days when I am more prepared, I prep the cups before the children arrive and pop them into the freezer so that we have frosty cups filled with ice cream ready and waiting for the root beer. Stymied, I lower my ice cream scoop, ready to defer to a five-year-old.

“Wait! Wait!” shouts four-year-old Everlee. “Let’s pour the root beer in one cup first and then add the ice cream. In another cup, we can do the ice cream in the bottom with the root beer on top. It will be an experiment!”

Our afternoon snack has become a collaborative scientific endeavor! A teachable moment has arrived, bringing with it opportunities to investigate, follow sequences and explore cause and effect—all wrapped up in an afternoon snack.

After making our predictions, we spend the next half hour engaged in deep scientific inquiry.

I recommend that you use clear cups so that the children can observe and compare the reactions from the side as well as the top.

During our investigation, we learned that if we added the ice cream first and the root beer second, the reaction created a big head of foam that flowed over the rim of the cup and all over our fingers and the counter. Who knew?

As the younger children oohed and ahhed over the overflowing foam, we concluded that the best way to add the ingredients depends on whether or not you are a fan of bubbly, magical, but messy foam!

Some of the children were napping when we started this experiment, which led us to discover that colder soda creates more foam than warmer soda. Which was just fine with the younger students, who just wanted the ice cream anyway.

This is a great opportunity to investigate variables such as: “Does it make a difference if the root beer is warm or cold? Does the temperature of the ice cream make a difference?  What happens if you use cups of different shapes and sizes? What happens if you use root beer that has lost its fizz?”

National Root Beer Float Day is August 6, 2022, which is a Saturday. Why not celebrate this fun holiday by conducting your own Root Beer Float investigation on Friday, August 5?

Just follow the instructions in our Science of Root Beer Floats Lesson Plan. Then click on the CONNECT WITH FAMILIES link on the left side of the page to download the Family Letter, customize it for your classroom and send it home with your students so that they can repeat the experiment with their families on Saturday—National Root Beer Float Day!

Everyone will appreciate this root beer toast to hot summer days, as well as the tasty, teachable moments. Cheers!

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