Information about Make a lava lamp with Fizzics Education | Kids Science Experiments

How to make a lava lamp

How to make a lava lamp

Follow FizzicsEd 150 Science Experiments:

You Will Need:

A clean Transparent PET bottle.

Oil, as an experiment you can try different types of oils and see how this affects you lava lamp.


Alka-Seltzer tablets

Food colouring

Making a Lava Lamp experiment ingredients
1 Making a Lava Lamp experiment - Red water in a plastic bottle

Fill the bottle about half full of water and add a few drops of food colouring.

2 Making a Lava Lamp experiment - pouring oil into bottle

Fill the rest of the bottle with cooking oil,and allow the components to settle and separate.

3 Making a Lava Lamp experiment - an alka seltzer tablet

Break an Alka-Seltzer tablet into quarters, and drop one piece into the bottle.

4 Making a Lava Lamp experiment with oil and water moving

Watch as the bottle swirls and churns like a real lava lamp!

Why Does This Happen?

Oil is hydrophobic, which means it doesn’t mix with water. It’s also less dense, which explains why it floats on top of the coloured water.

The Alka-Seltzer tablet contains two important chemicals acetyl-salicylic acid and bi-carb soda, a base. They don’t react while the tablet is dry, because they’re both solids, and can’t mix together. Once the tablet is dropped in the water however, these chemicals dissolve and mix together. When an acid and a base react, they produce lots of Carbon Dioxide (CO2). These bubbles of CO2 rise up through the liquids and push the water up into the oil, bringing the food colour with it. Once the bubbles of gas pop, the food coloured water then drop down to due it having a higher density than the oil… only to be lifted back up by more gas coming out of the Alk-Seltzer tablet!

See how the drop of water rise and fall? Blue-green algae cells are able to control their buoyancy, floating or sinking when they choose to. Inside the algal cells are vacuoles, tiny compartments that can hold gas. When the algae needs sunlight, it fills these vacuoles and floats to the surface. Then, it empties them, and sinks to the cooler water at the bottom of the river to find nutrients and grow. This allows blue-green algae to out-compete other algae in the water column, often resulting in dense & toxic algal blooms in our waterways.

Similar experiment: Dancing sultanas

Lava lamp version 2

  1. Fill the PET bottle half full of water and add a few drops of food colouring.
  2. Fill the rest of the PET bottle with cooking oil.
  3. Invert the bottle.
  4. Allow the components to settle and separate, this may take a few minutes.
  5. Add salt to the solution.
  6. Watch as the bottle swirls and churns like a lava lamp.

Because the oil and water don’t mix, you get some nice oily blobs circling around the bottle as you turn it upside down. Water is denser than oil and if left will settle to the bottom of the container.

Adding salt into the floating oil causes it to sink as it makes it more dense. However, once the oil reaches the bottom of the container the salt dissolves in the surrounding water, allowing the oil to rise back up to the top again.

Commercial lava lamps rely on heat from a lamp to expand oil, making it rise to the top of the lava lamp. This oil then eventually cools, contracting and falling down to the heat source to start the process again. This is known as a convection current which is very important in weather systems and ocean currents. Here is an experiment on establishing a convection current.

Learn more!


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