July 12, 2010

3 ways with volcanoes

We have continued with our weekly themes through the school holidays, and last week our theme was volcanoes and dinosaurs.  Now that the week is over it seems it was quite heavy on the volcano side of the equation.  So, here are 3 different ways to imitate a volcano that we tried this week.

Bicarb and Vinegar Volcano
bicarb & vinegar volcano
The traditional bicarb and vinegar volcano.  We made ours using a jar, which we wrapped in alfoil to make a volcano shape (we are all for quick here, my son wanted to get to the action, not make a model volcano).
Add 2 spoonfuls of bicarbonate soda to the jar.  Then, to make the volcano erupt pour in vinegar mixed with red food colouring.

Whats happening?  The chemical reaction between bicarbonate soda and vinegar produces bubbles of carbon dioxide gas, pushing the liquid out of the jar.
You can keep adding more bicarb and vinegar to make the volcano erupt again and again.

Milk Volcano
milk volcano
I have Preschool Playbook to thank for this idea. 
Add red food colouring to a glass of milk and have your child blow bubbles to make the volcano erupt.

Soda and Mentos Volcano
This is a demonstration volcano best done by an adult (or older child), because it is a bit tricky to co-ordinate all the actions. 
Roll up a piece of paper to create a tube for the Mentos.  The idea is to create a holder that when inverted will drop all the mints into the bottle quickly.
Find a flat surface outside for the soft drink bottle.  Open the lid carefully.  Invert the paper roll of mints over the opening of the bottle so that they fall into the bottle and stand back.  The liquid will explode through the neck of the bottle and may shoot up to a metre into the air.

Whats happening?  The soft drink has carbon dioxide dissolved in the liquid.  Some bubbles are released when the pressure drops as you take the lid off the bottle.  When you drop the mints into the bottle, air bubbles in the mints are released and seed the formation of larger carbon dioxide bubbles in the drink.  The bubbles force everything upwards out to the neck of the bottle.  The faster all this happens the more explosive your soda and mentos volcano will be.
This WikiHow – How to Make a Soda Bottle Volcano - has many more details and tips for this experiment and a more detailed explanation of what’s happening.  It’s worth reading because otherwise it is expensive to play around with bottles of drink and rolls of Mentos to get a good result.  And there is a photo of the eruption, which I don’t have because I couldn’t do everything and take a photo!

Inside a Volcano …
When molten rock accumulates inside a volcano it is under pressure, which keeps gases (like carbon dioxide, sulphur dioxide and water) dissolved in the liquid rock.  When pressure drops, at the start of an eruption, the dissolved gases form bubbles, increasing the volume of the magma, and causing the volcano to explode.  The more gases dissolved in the magma the larger the explosion. 

A few questions while you are doing these experiments will help children to think about volcanoes and how the experiments relate to real volcanoes.  You could ask them -
what do you think causes a volcano to erupt?
And as they do or watch the experiments ask
what do you think caused the lava to flow?
how are your eruptions and real eruptions alike?  How are they different?

If you are wondering about dinosaur activities Preschool Playbook runs a Dino Camp and has loads of great activities.


amandab said...

I needed some bicarb for baking this weekend, so husband played volcano yesterday, but he put the vinegar in first, then added the bicarb. It wasn't very impressive, so I am thinking the order in which you do it much be important to get the reaction right. Will get him to have another go and do it the other way round I think :)

Tina said...

This looks so fantastic, I will have to get the kids to try it!! Food colouring in milk - never thought of that, great idea. Much more impressive than our bubble bath bubbles with food colouring!
Your house looks so much fun!

Lucy said...

This is good website and good info. i think most of the volcanoes are hiding under the oceans. if science evolves greatly enough we may even have a chance of survival.

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