Make a Lava Lamp

Have you seen a lava lamp? These have been around for decades. The original one was invented in 1963 and they’re still popular today. The lights create strange, constantly moving, globular shapes.

Make one at home and have some science fun!

What you will need

Clear jar or bottle (a lid is handy)
Vegetable oil
Water
Cup or glass
Food colouring
Fizzing tablet, such as Alka-Seltzer

Method

Fill your jar or bottle around ¾ full with oil. Mix some water in a cup with food colouring and then add some to the jar or bottle, leaving around  2 to 5cm space at the top of the bottle.

Watch what happens to the oil and water.  Add a lid to the bottle and gently shake – do they mix?

Now add half of the fizzy tablet into the bottle/ jar and see what happens.  Add the other half of the tablet to continue the effect.  Can you see the lava lamp effect?

The science behind it

Oil and water are immiscible liquids, so they don’t mix (as we have seen with some of our other Store Cupboard Science experiments).  Water is denser than oil, so it sinks to the bottom and the oil floats on the top.  The food colouring is water soluble, so it changes the water’s colour.

When you add the fizzy tablet, it begins to dissolve and starts a reaction which creates gas bubbles (carbon dioxide gas).  As the bubbles rise (as these bubbles are less dense than both the oil and water) they rise through the layers and carry some of the coloured water with them to the top and then when the bubbles pop at the top, the water then sinks back down, creating the lava lamp effect.