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Explorit: Egg-speriment highlights buoyancy

By From page A4 | April 04, 2014

Does an egg float in water? If you think so, why? If not, can you make it float? What do you think it would take? Let’s try an experiment to find out.

You will need: a raw egg, two glasses of water, a measuring cup, a spoon, salt and a food scale. Start by filling two glasses half full with water. Use the measuring cup to make sure that you get the exact same amount of water in each glass. Add enough water to completely cover the egg.

Gently drop the raw egg into one of the glasses. Does it sink or float? Does it move slowly or quickly through the water? Why do you think this is happening?

You’re probably noticing that the egg has sunk to the bottom of the glass. That’s because the egg is heavier than the water. One reason why some things float on water is that they are lighter than the water.

How could you get the egg to float? Can you make the egg lighter? Or change its shape so that its weight is spread out? That’s one reason why large ships like aircraft carriers stay afloat.

Or can you change the water? If you can’t make the egg lighter, maybe you can make the water heavier. Try adding a spoonful of salt to the water and stir it in completely.

Keep adding salt one spoonful at a time and stirring it in until you see a change. When the egg starts to move, stop and notice what’s happening. Where did the egg move and how far? Did it stay in that spot or move back to the bottom of the glass?

Add salt until the egg floats to the top and doesn’t sink any more. How much salt did you have to add? And why do you think adding salt makes a difference and causes the egg to float?

Stirring the salt into the water adds more molecules to the water, making it denser, basically making the water heavier. Add enough salt and eventually the water will be heavier than the egg so the egg will rise to the top and float.

That’s why it can be easier to float in a salt-water sea than a fresh-water lake. The Dead Sea that borders Israel, Jordan and Palestine is one of the saltiest bodies of water on Earth. It’s 10 times saltier than the ocean! That makes it a very easy place to float, but a hard place to swim since it’s hard to move through water that is so dense.

Water, the many ways it can change and how we interact with it will be one of the fun explorations on which Explorit’s summer science campers will embark. They’ll explore the chemistry and physics of water as well as differences between fresh- and salt-water habitats for plants and animals while learning about conservation.

Registration for this and all of Explorit’s camps is open now at www.explorit.org. And stay tuned for more information about Explorit’s new exhibition on water coming this fall!

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Explorit’s coming events:

* Explorit’s “Beautiful World: Science and Art” exhibition is open to the public from 1 to 5 p.m. every Wednesday, Saturday and Sunday and every Friday from 3 to 6 p.m. Admission is $5 per person; Explorit members, teachers and children 2 and under are free.

* Summer Science Camp is coming! Registration is open now. Visit www.explorit.org for more information or to register.

— Explorit Science Center is at 3141 Fifth St. For more information, call 530-756-0191, visit www.explorit.org, or “like” Explorit on Facebook at www.facebook.com/explorit.fb.

Lisa Justice

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