We will need:
- drinking glass, the wide and low work best,
- 1 / 4 cup vegetable oil,
- 1 teaspoon of salt,
- food colouring (optional) can be any colour, but the lava is red:).
- Fill the glass with 3 / 4 water;
- Add 5 drops of food colouring;
- Throw, slowly and gently, the vegetable oil in the cup. See how the oil floats on top;
- Sprinkle the salt over the oil;
- Watch the lava bubbles up and down in your glass;
- If you want to continue to observe the effect just add another teaspoon of salt to the oil.
Of course inside the glass we don’t have thru lava, the true is less fantastic, it looks like lava but its like those cheep lava lamps used in 1960’s.
First, the oil floats on water because it is lighter than water.
Then the salt is heavier than oil and sinks in water. When this happens the salt takes a bit of oil with it when goes down and the bubble is formed, when salt dissolves ... bang! Oil goes back up to the surface of the water.
If your young restless mind want to take the step further try to answer these questions:
- How long will the effect stands if you continue to add salt?
- Changing the type of oil produces different results? and olive oil?
- In addition to salt, is there any substance that works?
- Does the height or shape of the glass affects the results?