Food Buoyancy

Let’s do some kitchen experiments to see what may surprise you about what sinks or floats!

What you will need:

  • Fruits and vegetables, including some with and without thick peels or rinds and some heavy and light ones. Examples: banana, orange, grapes, apple, bell pepper, potato, peas, zucchini;
  • A large bowl or tub;
  • Knife or knives;
  • Water;
  • Optional: Scale, cans of diet and regular soda, salt, egg

Here’s what to do:

  1. Fill your bowl or tub with enough water to cover the biggest produce.
    • Examine your items and compare their sizes, shapes and weights.
    • Do some feel solid or hollow?
    • Which ones do you think will sink or float in water?
  2. Test your predictions by placing each item in the tub to see if it sinks or floats.
    • Does removing a rind or peel change the buoyancy?
    • Does ripeness affect how items sink or float?
    • What happens when you cut the food into smaller pieces?

Take it further:

  1. Does a can of regular soda float differently than a can of diet soda?
    • What about other diet and regular drinks?
  2. Use salt to test how making water denser affects buoyancy.
    • Fill two wide and tall glasses (big enough around to easily hold an egg) about half full of water.
    • Dissolve 4-5 tablespoons of salt in one of the glasses.
  3. Try to float an egg first in the plain water then in the salty water.
    • What do you notice?
  4. What about trying to float thin slices of potatoes or other produce in either glass?
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