What Floats Your Boat?

What kid doesn’t like to play with water?  Add a bit of science and math to your water play next time with this easy experiment to set up at home.  I used to to this same experiment with my middle schoolers in the classroom to demonstrate concepts in buoyancy but for the little ones, it is just fun!

Here’s what you need to get started:

  • small bin or deep dish for water or even your water table!
  • water (I added some blue color for fun)
  • Foil
  • pennies or small rocks

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Add some water to the bin.  My kids love colored water so we added a drop to simulate ocean water.

The tricky part is making the foil boat.  Younger kids might have trouble with this and might tear their boats.  Feel free to help them. Ours looked like bowls.

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Place the foil boat in the water and make sure it floats and doesn’t have any leaks.

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Next, we added pennies, one by one, to the boat.

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You will be amazed at how many pennies this little foil boat can hold!

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And then there was one penny to many… and the boat finally sank!

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Lastly, they colored in their lab sheet and had to write the number of pennies their boat held before sinking.  There you go!  Math, science, coloring and some healthy sibling competition:)

Extensions for older kids: Compare what happens to 2 identical pieces of foil when placed in water: one in the shape of a boat and one wadded up super tight to minimize the amount of air trapped inside.  Why do you think this is possible?  Also, try this experiment with salt water.  Predict what effect salt water would have on the boat’s ability to carry cargo.

The Science behind the Activity:

When doing this experiment with older kids, I discuss the concept of buoyancy, which is the ability of an object to float when placed in a fluid.  Surface area greatly affects the buoyancy of an object.  The larger surface area allows the force (weight of the cargo/pennies) to be spread out over a larger area, thus allowing the boat to float even with the “cargo”. The larger surface area displaces more water.  This is why a large hull in a ship is able to float on water.  And if the ship is floating on salt water (like the ocean) it can carry even more cargo since salt water is denser than pure water.  It’s a bit more complicated than my simplified explanation, but hopefully you get the point.  And for the little ones, it’s just fun to sink the boats:)

For a more detailed explanation click on this link:

http://www.coolscience.org/CoolScience/Teachers/Activities/FoilBoats.htm

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