Lava in a Cup:
Hello everyone! I have been busy researching science experiments for the Science Day I am holding on Saturday. I thought I’d share some of my favourites with you! Here’s the first:
*A clear drinking glass
* 1/4 cup vegetable oil
* 1 teaspoon salt
* Water
* Food coloring (optional) 
- Fill the glass about 3/4 full of water .
- Add about 5 drops of food coloring – red for the lava look.
- Slowly pour the vegetable oil into the glass. See how the oil floats on top
- Now the fun part: Sprinkle the salt on top of the oil.
- Watch blobs of lava move up and down in your glass!
- If you liked that, add another teaspoon of salt to keep the effect going.
First of all, the oil floats on top of the water because it is lighter than the water. Since the salt is heavier than oil, it sinks down into the water and takes some oil with it, but then the salt dissolves and back up goes the oil!
The project above is a DEMONSTRATION. To make it a true experiment, you can try to answer these questions:
1. How long will the effect go on if you keep adding salt?
2. Do different kinds of food oil give different effects?
3. Will other substances (sand, sugar. etc.) work the same as salt?
4. Does the height or shape of the glass affect the experiment?
Found at: http://www.sciencebob.com/experiments/lavacup.php
[pb_builder]