Dancing Oil

If you've ever heard someone shout "Eureka!" when they figured out the solution to a problem, you can thank today's real-life mad scientist, Archimedes. Among his many discoveries and inventions was the technique of measuring an object's density based on how much water it displaces. Learn more in this short video from TED-Ed.

Density can be a tricky concept. Let's take another look.

When you think about layers of liquid, you probably think about things like root beer floats, with the ice cream melting at the top and the root beer below (yum...). But did you know you can stack some liquids up like blocks? That's because some liquids have different "densities" than others. Check out this article to learn more and see some liquid stacking in action.

Think about these questions after watching the video:

1. Why do you think layers of different liquid were able to form in the container? Why didn't they all mix together?

2. Why do you think certain objects sank while other objects were able to float?

Wait, if things like metal are denser than water, why don't giant boats made out of metal sink straight to the bottom? Let's find out with Wonderopolis.

Oil spills are a good example of how oil and water don't mix. Instead of dissolving in the ocean, the oil from a tanker ship or drilling rig instead sits on top of the water and spreads—sometimes for hundreds of miles. It's a huge mess that can do a lot of damage to wildlife. But scientists can also use the way oil behaves to clean it up. Find out how in this video from Discovery News.

We loved Dance Revolution week so much that we wondered if we could make chemicals dance, too. Turns out, we can—and you can, too!

To get started, you'll need an empty jar, water, a cup of vegetable oil, and some salt. (Younger kinda campers will also need some help from an adult.)

Once you have your supplies, click the button and follow the directions to begin the dance of the oil bubbles.

All this talk about floating is making us eager for some time in the water. If you have access to a pool and the weather's nice, today is the perfect day to go practice being buoyant! If not, give this swim-inspired workout a try so you're ready next time.