A clear glass
¼ vegetable oil
1 teaspoon salt
Fill ¾ of the glass with water.
Add 5 drops of food colouring.
Carefully pour the vegetable oil into the glass. You will notice the oil floating on water.
Now, sprinkle some salt on top of the oil. You will notice the contents turn to lava blobs.
How does this work?
When we pour oil on water, it floats since it is lighter than the water. Later, when salt is added,it pulls down some amount of oil to the bottom of the glass. But when the salt dissolves in water, the oil blobs rise to the surface again, forming lava blobs. We can see the reaction occurring again as we add more salt.