Density and Buoyancy: Making Eggs Float (Document)
Have you ever tried to float in an ocean? How about in a lake? Did you notice a difference? I've tried to float in a lake and in an ocean, and I thought it was a lot easier in the ocean, because the salt helps hold me up. And Katie N. of Preston, Washington, says that salt can do amazing things when put to the test. She says that we can use it to have an egg float in water. Here's what happens when we drop an egg in a glass of water without any salt in it. Bye-bye, egg. It sinks right to the bottom. I know. Now let's see if we can add salt and if that'll make it float. So do you want to add one tablespoon first? Sure, we'll try that. So that's one. Now we'll stir it up. It kind of went up. I know, it, like, jumped, kind of. Let's just stir it a tiny bit. It's cool, it looks kind of like a cloud. Yeah. Oh, it didn't make too much of a difference, so why don't you try another tablespoon? Two, whoa, yeah, it goes way up. It takes a little while for the salt to dissolve into the water, then it starts floating. Okay. Three. Oh, wow, that went way up. Stay up, little eggy. Stay up. It's, like, right in the middle, kind of. Yeah. This is our fourth. Oh! Wow! It floated! Four-- that's right at the top. It's so cool. Jim of Arizona also experimented with this, and he sent us this Sci Scoop. He said that when we add salt into the water, we're smooshing more molecules into the water. It makes the water more dense, so when there was no salt in the water, the egg was more dense than the water and the egg sank. But when we added salt to the water, the water was more dense than the egg, and the egg floated. Here's a cup of fresh water and here's a cup of salt water. They're taking up the same amount of space, but if you weigh them, you can see that the salt water weighs more than the fresh water. Okay. So I'll fill it up on this side. Okay, so that's that. And...Fill it up right over...Fill it to the 200. Yup. See? Look how much the salt water...Look at the difference. So they're the same amount of water, but there's more stuff inside the salt water, so the salt water's more dense, so it's heavier. Try this at home. Think of a question that you want answered, like, would sugar dissolved in water help an egg float? How about soap? Make a prediction. Test it out.
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