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Wednesday, August 24, 2011

Investigating in Science using a Model

We wanted to find out how pumice is made. We knew it was an igneous rock that comes from a volcano but not how it was formed.

Sadly it is too dangerous to visit an actual volcano while it is erupting so Miss Harrison said we could learn about pumice by creating a model to replicate what happens.

Luckily for us the model taught us things as well as tasted good!!!!!

We got to make Hokey Pokey because it is formed in much the same way as pumice.

First you boil up some sugar and golden syrup. This is like the hot magma under the ground.

Then you add the baking soda to create the eruption.

The baking soda creates a chemical reaction with the hot liquid to produce a gas called carbon dioxide. The gas makes the mixture expand and puff up as it fill with lots of air bubbles.

When a volcano erupts the magma explodes out as lava and also there are lots of volcanic gases. If the lava mixes with the gases it puffs up and expands.


As the hokey pokey cools the air bubbles are trapped in the mixture.

This happens to the puffed up lava too. It cools really quickly and traps all the air bubbles. The rock that forms is called PUMICE. That is why pumice is really light and can float - it is filled with lots of little air bubbles and holes.

When you observe pumice carefully it looks a lot like the hokey pokey.



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