Homemade Lava Lamp

Here's what you'll need...
  • an empty bottle
  • vegetable oil
  • water
  • food coloring
  • a funnel
  • Alka-Seltzer tablets

Everyone has probably seen a lava lamp with the cool blobs that move up and down the light. Lava lamps are really neat piece of science. Here's a homemade lava lamp experiment for you to try at home!

Both real lava lamps and our homemade version use properties of density to make the blobs move up and down. Density is the mass per volume, basically the weight in a certain amount. Density gives a way to look at one weight and compare it to another. To understand density let's look at our experiment.

Interestingly enough the water sank to the bottom and the oil floated on top. This is because the oil is less dense then the water. This means if we took the same volume (a fancy word for amount) of oil and water the water would have more weight then the oil which makes it more dense. Since the water is more dense then the oil it ends up on the bottom. If we added another liquid that was more dense (more weight per volume) then water, where would it end up?

The oil and the water stayed in their nice seperate layers because they are a good example of immiscibility liquids, which is a fancy science way of saying they don't like to mix. Why don't they like to mix? It's because of their polarity! All molecules have a polarity to them. They can either be polar like water or non-polar like oil.

Water molecules are polar which simply means they have a positive charge at one end and a negative charge at the other, they like to mix with other polar molecules because their positive charge attracts the negative charge of another molecule causing the molecules to stick together! Oil molecules are non-polar meaning they have no extra positive or negative charges. So the water molecules trying to attract a negative charge of another molecule can't attract the non-polar oil molecules. Becasue of this chemistry we get the seperate layers we need for our experiment

So the liquids don't mix because they are immiscible and the water is on the bottom becasue its more dense. How do we create the lava lamp effect? Well that is the alka-seltzer's job. When you drop the alkaseltzer in it sinks to the bottom and starts to dissolve in the water. When it dissolves it produces a gas which becomes less dense and floats to the top carrying some of the water with it. Once it reaches the top of the lamp the gas escapes so the water drop is once again more dense then the oil and sinks to the bottom again.

Experiment with this project! Try adding different liquids. Can you find one that is more dense then water? What happens to your lava lamp if you use cold water or hot water? Share your results with the ScienceOffCenter team!