This simple salt lava lamp is a fun twist on the more traditional homemade lava lamp that uses a fizzy tablet. The salt lava lamp doesn’t look quite a good, and isn’t as reusable but is still a nice science activity for learning about density.
A glass jar or glass
Vegetable oil – or other cheap cooking oil
Food colouring -optional
Fill the glass or jar about three quarters full.
Top up with vegetable oil to almost the top.
Sprinkle salt slowly for about 10 seconds over the top of the oil.
Sit back and watch!
Keep adding more salt to keep it going.
Why does a salt lava lamp work?
Oil floats on water because it is less dense than water. Anything less dense than than water will float. We’ve demonstrated this before with a basic density jar.
Oil and water are immiscible liquids, they don’t mix.
When you pour salt onto the oil it sinks through the oil and into the water carrying a little oil with it.
The salt dissolves in the water which releases the oil allowing it to float back up to the oil layer.
Make a traditional lava lamp. These use oil, water and an effervescent vitamin tablet.
Another fun way to learn about density is to make a density column using liquids with different densities.
If you make your own salt lava lamp, don’t forget to send me a picture!
Last Updated on September 12, 2022 by Emma Vanstone
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