How to make a lava lamp science experiment : Fizzics Education


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How to make a lava lamp

How to make a lava lamp

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You Will Need:

  • A clean Transparent PET bottle or clear cup.
  • Vegetable oil, as an experiment you can try different types of oils and see how this affects your lava lamp.
  • Water
  • Alka-Seltzer tablets
  • Food colouring
  • Funnel


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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. If you are doing this in a cup, add the whole tablet!

4 Making a Lava Lamp experiment with oil and water moving

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

6 A man watching bubbles pour out of a large measuring cylinder

Get the Unit of Work on States of Matter here!

  • What are the different states of matter?
  • How does heat affect the size of materials?
  • How does liquid nitrogen affect materials and much more!

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8 Teacher showing how to do an experiment outside to a group of kids.

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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 bicarbonate 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 drops down to due it having a higher density than the oil… only to be lifted back up by more gas coming out of the Alka-Seltzer tablet!

See how the drops of water rise and fall? In some ways, this is a bit like how blue-green algae cells are able to control their buoyancy, where they can control if they float or sink using gases. Inside the algal cells are vacuoles, tiny compartments that can hold gas. When the algae need sunlight, it fills these vacuoles and floats to the surface. Afterwards, the algae empty their vacuoles and the algae then sink 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 denser. 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.

Variables to test

More on variables here

  • What happens if you cool the alka-seltzer tablet in the freezer first?
  • What happens if the oil is warm vs cold?
  • Try different viscosities of oils (canola oil, typewriter oil. olive oil etc)
  • Try lots of alka-seltzer tablets vs. not many

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A man with a glove above a liquid nitrogen vapour cloud

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21 thoughts on “How to make a lava lamp

    1. Hi! This will run for around 30 seconds to 1 minute and then slow down until all the gas has left the liquid. The time difference is mainly due to the temperature of the liquid and the amount of Alka Seltzer tablets that you add. Have fun!

  1. Could you add another Alka-Seltzer tablet after the first one fizzes out and get the same result?

  2. I am in 7th grade this is my first time choosing a lava lamp as my science project do you have to use a specific oil, or can you use different ones?

    1. Hi! As its a science project you should show different oils to se if there is a difference. Try vegetable oil, olive oil, baby oil and others. If there is no difference, that is also your result. All the best!

  3. I want to try this science experiment with my preschoolers. What would a kid friendly objective be for this lesson?

    1. Sure thing!
      Investigative question: How long can we make the lava lamp run?
      Try different amounts of materials to find out as a variable test 🙂

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