Floating Egg

Yesterday I presented Selena with two jars of liquid, and two eggs. My goal was to teach her how to think like a scientist and to learn about density. She of course was intrigued over the egg in jar B floating and immediately went to work on figuring out why. We first defined the words, Dense and Density. Dense is defined as closely compact in substance and Density is defined as State or quality of being dense. We chose several objects such as a rock and a piece of wood, Selena easily determined the rock was more dense then the wood, due to to their make up, the rock would not have room for air pockets where as the wood be less solid and would have room for air pockets to help it float. Let me be clear here I had made sure she realized the weight of the object had no bearings on this experiment.

Now after examining the eggs she determined they were exactly the same in the fact that they were both chicken eggs. She determined it had to do with the liquid. Through yes and no questions she had to come to her conclusion.

Questions:

1. Is A only water? Yes
2. Is B only water? No

1. Does B contain something found in our kitchen? Yes
2. Is that substance a powder? No

1. Is that substance granulated? Yes
2. Is that substance sweet? No
3. Is that substance salt? Yes

Her conclusion then was written, "The egg in B floated because we changed the density of the water, by adding salt."

Why did this happen? She concluded that the salt added more density to the water in jar B, which held the egg up, where as the the water in jar A had less density and not able to hold the egg up. Of course this led to many discussions, such as the difference between the Ocean and a simple lake.

She then became curious over other liquids, so we took out the oil. She discovered that oil is less dense then even water. I know the least dense liquid is mercury, but of course I am not going to allow her to play with mercury.

This was a fun experiment, and even if you have a younger child, it is fun to see the amazement on their face. If you have an older child it is a cool way to introduce density and it's properties. It is simple and a fun way to help your child learn how a scientist think.

I want to leave you with one more fact, it is called the Universal Law of Density:

Less Dense

More Dense

The line represents water or liquid, if an object is less dense it will float, more dense it will sink. By changing the density of the water does not change this Universal Law but does change the results of some objects and their ability to stay afloat. The more Dense an object is will not be changed with the change in the density of the water. 

Hope you have fun sharing this with your kids.