This little balloon project is a fun way to teach kids about buoyancy, and more specifically about how fish can swim in the water without either floating to the top or sinking to the bottom. As a bonus, it starts out as science and ends as a bath toy!
To set up, first insert a marble into each of three uninflated balloons. You’ll have to open the neck of the balloon wide to do this, which can be a bit tricky.
Using a funnel, fill one balloon with 1/3 cup vegetable oil. Fill the second ballon with 1/3 cup water. Blow up the final balloon with air until it’s roughly the same size as the balloons with liquid.
You can add fishy faces or fins with permanent marker, if desired! Next, fill a craft bin with water, and set your fish loose. Travis’s hypothesis was that the oil-filled “fish” would be the one to neither sink nor float, and he was so proud to be correct!
As you can probably guess, the water + marble sinks to the bottom. The oil + marble manages to be midway in the water, just like a fish swimming. The air + marble floats on top…not where a fish wants to be!
Once the science was done, we brought the fish upstairs at bath time, where they made for extra fun!
