What you need:
Vegetable oil, water, a glass, red food colour or poster colour salt and a flashlight
What to do:
1. Fill three quarters of the glass with water. Add the red colour into it
2. Slowly pour the vegetable oil over the water. What happens?
3. Now, sprinkle some salt into the glass. Observe what happens.
4. Continue to gradually add salt.
What happens?
When oil is poured into the glass, it separates into a layer that floats on the water. When you add more and more salt the oil starts bouncing around in the water! Why? We all know that everything on Earth is made up of small particles called atoms which give mass to an object. The closer these atoms are packed together, the denser an object is said to be.
Now that we know density, we can understand floating. Simply put, in order to float in a liquid, an object needs to have lesser density than that liquid. Since oil’s density is lesser than water, it floats on the water’s surface like film. Salt is denser than the oil and starts sinking to the lower water layer. But the salt takes some oil with it. As the salt reaches the water, it begins to dissolve. That sets the oil free and it floats back to the top. As you add more salt, the amount of oil sinking and floating back increases until you get the effect of blobs of oil bouncing about in the red liquid. If you shine a flashlight behind the glass, the whole effect looks like a lava lamp. Pretty neat, huh?
Picture Credit : Google
