“EUREKA!”
~ ancient Greek philosopher Archimedes, (according to the legend of when he discovered the science of water displacement)
One of my favorite science activities to do when my kids are bored and stuck indoors is to make aluminum foil boats. Whose boat will hold the most pennies? Next time, I'm going to give them cardboard and toothpicks to reinforce their foil boats!
While kids can intuitively learn a lot about floating just by doing this activity, it’s a great jumping off point to talk about density and water displacement.
If you need a refresher - density is about weight and size.
A metal spoon is denser than a plastic spoon - they're the same size but the metal spoon weighs more.
A metal paper clip is denser than a plastic spoon - they weigh about the same, but the paper clip is a smaller size.
When a metal spoon sinks, the spoon is pushing a spoon-sized volume of water out of the way to make room for itself at the bottom of the tub. That’s water displacement!
That’s the quick science refresher for the grown-ups, but here are some much more fun ways for the preschoolers, kindergarteners, 1st and 2nd graders to engage with this STEM topic!
(Just a reminder - I am never paid to mention any of these resources; there are no affiliate links.)
Sink or Float Science Videos
Why Do Ships Float? from SciShow kids
Giant Squid is wondering how a giant cruise ship floats. Isn’t it too heavy? This video doesn’t go into the math of explaining density, but it does explain water displacement, how the cruise ship is so wide that it displaces a lot of water. A great explanation for preschoolers!
Wicked Water Experiments from Science Max
Can Science Max make a giant tinfoil boat that can carry him? (Spoiler: Yes, but only after falling into the pool a bunch of times!) Plus Pirate Swabby explains mass, volume, and density.
Sink or Float Science Picture Books
written by Lynne Berry, illustrated by Matthew Cordell
How will Archie the Goat and Skinny the Hen cross the moat? They could just take the drawbridge but… “This is no time for a drawbridge. This is a time for science!”
This very silly story surprised me with the legitimately great science! They learn that the full barrel sinks of course. Then they learn that the empty barrel floats, but also rolls and tosses them into the water. A partially full barrel sinks just a little bit into the water to help their makeshift boat stay upright.
written by Kimberly Derting and Shelli R. Johannes, illustrated by Joelle Murray
Vivi has a lot of questions on her field trip to the aquarium. Like, how do fish keep from sinking? (Good question Vivi, I didn’t know the answer myself!) Turns out a fish’s swim bladder changes its density. There’s a swim bladder activity using a balloon in the book too!
written by David Adler, illustrated by Anna Raff
For kids that want a deeper scientific explanation, this book builds their understanding of density and water displacement step by step. It even explains why ice floats in water, and why salt water is denser than fresh water.
Sink or Float Science Activities
from PBS Kids
This activity is so easy to set up. To go the extra mile, you can practice the scientific method of defining the question, making a hypothesis, gather data, analyze the data, and make conclusions. (PBS Kids has a colorful Cat-in-the-Hat themed chart that you can use to record your data.) Give your kids metal spoons and plastic spoons and see if they can make a conclusion that explains why one sinks and one floats!
from Siemens Knowledge Hub
Oranges float! But did you know a peeled orange sinks, even though it weighs less without the peel? It’s because there’s lots of air bubbles in the peel that make the unpeeled orange float. This makes an orange an unexpectedly great example to show the difference between weight and density!
from SciShow Kids
Make an aluminum foil boat! Whose boat can carry the most marbles? (Or pennies, or beans…) You could try a canoe design like these kids Sophie and Zane, or try your own design. Definitely try a flat sheet of foil or a crumpled up ball of foil too to compare with your boats!
That’s it for the science of flotation!
Next month my kids will be back in school, so that seems like a good time for the science of germs. Until next time, have fun sinking & floating!
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