Volcanoes hold great fascination among children (and grown-ups!). Here are some ideas for making your own and experimenting with the best eruptions.

First you need to find out about volcanoes. Do you have any books about them? Try looking up ‘volcano facts for kids’ on the internet. There are some great pictures and videos available too. Do you want to make a cinder cone, stratovolcano or shield volcano? Then think about what to make it out of. You could use sand, salt dough, paper mache, Lego, junk…be creative. It will get messy though! Whatever you make it out of, it needs to be on a big tray to catch the ‘lava’. Put a small bottle inside to be the ‘magma chamber’, make sure you don’t cover the top of this.

Experimenting with eruptions 

There are a few options for making your volcano erupt. You can try them out (on a tray or in the sink!) before choosing one to go in your volcano model.

The most common is vinegar and bicarbonate of soda. Just mix a tablespoon or two of bicarbonate of soda with about a cupful of warm water. Pour it into a small bottle, add a squirt of washing-up liquid and then vinegar. You can experiment with different amounts of vinegar and powder.

Or try a mini version of Coke and Mentos. Take a small (250ml) bottle of diet cola, drop in three Mentos and decide if that’s the eruption for you!

My favourite is a much slower eruption but it just keeps on going for ages. This one needs some 6% hydrogen peroxide (available cheaply in all chemists, don’t use any stronger than 6%). Pour 100ml into a small bottle, add a good squirt of washing-up liquid and then add the magic ingredient: a spoonful of yeast mixed with warm water. The foam ‘lava’ is safe to play with, it’s just soapy water.

How do these work?

  • The vinegar and bicarbonate of soda react together because they are an acid and an alkali (see the colour changing cabbage experiments for ideas about this). The chemical reaction makes a type of salt, some more water and carbon dioxide gas. It’s the gas the makes it into an eruption, the washing up liquid just catches some of this gas to make a load of bubbles.
  • See the Fizzy Fountains experiment for ideas about Coke and Mentos.
  • The final eruption is called ‘elephant’s toothpaste’ as it looks a bit like a massive heap of toothpaste being squeezed out of a tube. The hydrogen peroxide can break down to make water and oxygen gas. It usually happens pretty slowly but the chemicals in yeast speed it up. All the gas bubbling up through the washing up liquid is what makes all the foamy fun!