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Rescue the Egg

수영 학습

Why do you float better in salt water than in fresh water?

Have you ever swam in pools and seas? Then you probably know that your body floats better in the sea than in the pool. Do you know why? This science activity will tell you the reason why you can float better in salt water than in fresh water. Here we go!

 Materials

  • 3 cups

  • 3 eggs

  • salt

  • sugar

  • spoon

  • water

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 Procedures

  1. Pour a cup of water into 3 cups.

  2. Leave the first cup of plain water.

  3. In the second cup, add 3 tablespoons of sugar and stir.

  4. In the third cup, add 3 tablespoons of salt and stir.

  5. Place an egg in each cup. Observe what happens.

Science Behind It

An egg sinks in water, that’s because an egg is more dense than water. More dense means it is more crowded and heavier than the other. Same as plain water, the sugar water was not dense enough to make the egg float. But, why does the egg in salt water float? When the salt is added to the water, it increases the density of the water and hence the density of the egg becomes lesser than the salt water. So an egg is more dense than water and sugar water, and less dense than salt water.

 

However, you can make the egg float on sugar water. How? Add more sugar! If you add more sugar to the sugar water, it increases the density of sugar water. The sugar water is now more dense due to the added sugar. Try this with another materials such as baking soda, starch or flour. If the mixture is more dense than an egg, the egg floats on top.

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