What you will need :
1. plastic bottle
2. food colouring
4. vegetable oil
5. Alka -seltzer tablets
1. fill a 1/4 of a bottle with water
2. Top it up with vegetable oil
3. Add 12 drops of food colouring of your choice.
4.Cut the pill in half.
5.Drop the pill in the bottle.
6.And enjoy the show.
How it works:
The oil and water you added to the bottle separate from each other, with oil on top because it has a lower density than water. The food coloring falls through the oil and mixes with the water at the bottom. The piece of Alka-Seltzer tablet you drop in after releases small bubbles of carbon dioxide gas that rise to the top and take some of the colored water along for the ride. The gas escapes when it reaches the top and the colored water falls back down. The reason Alka-Seltzer fizzes in such a way is because it contains citric acid and baking soda (sodium bicarbonate), the two react with water to form sodium citrate and carbon dioxide gas (those are the bubbles that carry the colored water to the top of the bottle).
Adding more Alka-Seltzer to the bottle keeps the reaction going so you can enjoy your funky lava lamp for longer. If you want to show someone later you can simply screw on a bottle cap and add more Alka-Seltzer when you need to.