Science Experiments

Do Eggs Float?

Art by Brenda Pepper

In water, is an egg more like a boat or a rock? The answer depends on what’s in the water. Try these three experiments to see for yourself. Do them near the kitchen sink, as you might spill some water.

What You’ll NeedDo Eggs Float?

  • a coin
  • an uncooked egg (always wash your hands before and after handling an uncooked egg)
  • a piece of cork or a piece of light plastic packing material
  • a spoon (rinse and dry off the spoon between these three experiments)
  • two water glasses
  • salt
  • a paper napkin

What to Do

  1. Use a spoon to carefully lower the coin, an uncooked egg, and a piece of cork into a glass of water. (If you don’t have any cork, try a piece of light plastic packing material.)  You'll see that the egg and coin will sink, and the cork will float.
  2. Now remove the objects, and add two tablespoonfuls of salt to the water. Stir until the salt dissolves. Now lower the objects into the saltwater. The coin still sinks, and the cork still floats. But the egg does not sink. Instead, it floats near the top of the water. (If it doesn’t, dissolve more salt into the water.)
  3. Remove the objects again. Using a tall water glass, fill the glass one-half full with saltwater. Now pour a layer of tap water on top of the saltwater without mixing them up. Here's how to do that (as shown in the drawing above):

    Unfold a paper napkin, and put one corner of it down into the tall glass so that the napkin covers the surface of the salt water. Hold the napkin in place. Slowly, steadily pour in tap water until the glass is almost full. Carefully pull out the paper napkin.

    Now use the spoon to  lower the objects into the water again. Again, the coin sinks and the cork floats. But now the egg sinks to about the middle of the glass. It goes to the bottom of the tap water but floats in the salt water. Push down on the egg gently with a spoon to see it return to the same level.

How It Works

Do Eggs Float?

Eggs are denser than tap water. That means an egg weighs more than an egg-sized amount of tap water. In the same way, a nail is heavier than a wooden stick of the same size because steel is denser—packs more weight into the same space—than wood.

In the first experiment, the egg sinks in the tap water like an air-filled balloon dropping through the air. But in the second experiment, dissolving salt in the water makes it more dense than the egg. Here, the egg rises like a helium-filled balloon in the heavy air (saltwater) around it.

Of course, you can’t make water light enough to make a cork sink or dense enough to float a coin. But if you like, try these experiments with a hard-cooked egg instead of a raw one. Do you notice any difference in the results?

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