06/26/2014
Crazy Russian Hacker (youtube and facebook) did a video about fun experiments to do with eggs, they are all fairly safe but may require parental supervision. However, since it is summer, some of these could be fun to do for some learning while the sun is out. (If he eats something, that is NOT recommended by FST! So please do not try the "eating" parts of his experiments at home)
It was asked, why does an egg float in the middle of a glass filled halfway with salt water, and halfway with freshwater?
This is a density experiment. Density is a property of matter (solids, liquids & gases) and is defined by the mass of an object per 1 unit volume, or grams/mL. There are many ways to think about it but to help visualize it first, picture a golf ball and a ping-pong ball. They are about the same size in diameter. So they take up the same amount of space on earth, that's their volume-- and it's equal! But because the golf ball weighs more than the ping pong ball, it has a larger mass than the ping-pong ball as well**. So, because the golf ball has a larger mass than the ping-pong ball but they both take up the same amount of space (same volume) the golf ball must have a greater density.
We can compare density of solids to those of liquids as well, using the same idea. If we were to take an equal volume of the solid and liquid and compare the mass of the two we could determine which has a greater or lesser density.
Now, the egg is more dense than fresh water, so it sinks; however the egg is less dense than the salt water, so it floats. Then salt water is more dense than the regular water, so the fresh water floats atop the salt water in the third glass (though you cannot see that). Because of all these properties the egg will float in the middle of a glass that is half-filled with salt water and half filled with plain fresh water.
Any other questions please don't hesitate to ask
**(note: weight and mass are similar but different! weight is mass times about 10, the exact reason and formula can be discussed later, but knowing they are proportional allows you to know that if something weighs more it must have a higher mass)
https://www.youtube.com/watch?v=M419D6LsqZU
Maine channel CrazyRussianHacker http://www.youtube.com/user/CrazyRussianHacker