Original Source

Ingredients:

• Clear drinking glass or beaker
• Food coloring (optional)
• ¼ C vegetable oil
• 1-2 tsp salt
• Water

Directions:

1. Add water to glass
   Fill the glass about ¾ full of water.
2. Add food coloring, then oil to water
   Add about 5 drops of food coloring to the glass of water. Slowly pour the vegetable oil into the glass. Watch as the oil floats on top.
3.  Sprinkle salt on top of the oil
   Sprinkle the salt on top of the oil, and watch the blobs of “lava” move up and down in the glass.
   Kick it up: add another teaspoon of salt to keep the effect going.

Why?

The oil floats on top of the water because it’s lighter than the water. Salt is heavier than oil, so it sinks down into the water and takes some oil with it. Once the salt dissolves, the oil will go back up to the top. Pretty neat!

Read more:

Learn more about liquid density with the Seven-Layer Density Column

Why does oil float on water?

What’s happening when I pour salt on the oil?

Additional questions to ask from Science Bob:

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?

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