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2018 - Term Three - Week Four - Yip, Yet More Concrete and More Chemistry!

Hi everybody - it’s been another packed week and all our makers have been very busy..

Our weekend groups have (almost) finished their concrete pots and with it our first chemistry block.  Everyone was excited to be un-screwing the moulds and seeing how well their concrete had set.  A bit of the finer detail was a little lost on some but really things came out very well!


To make sure our pots are watertight we will be putting a couple of coats of concrete glaze both inside and outside.  We did the first coat this week and will be adding another next.  The glaze looks awesome once it has dried (it’s still quite wet in the photos as you can see) and provides further support for the edges and detail of the designs.  I'm looking forward to being able to show everybody the finished product.

Once our pots were fully coated we headed back into the studio to continue our chemistry.  We talked more about molecules and chemical reactions - particularly the fact that in all reactions nothing is lost.  On an atomic level what goes in must come out, even if it has changed into a completely different set of molecules with a completely new colour, shape or smell.


The first experiment we used to demonstrate this was the classic Vinegar and Baking Soda - or as we know it - Acetic Acid and Sodium Bicarbonate.  Combine the two and you get a mix of Sodium Acetate and Carbonic Acid.  The Carbonic Acid quickly changes into Water and a gas - Carbon Dioxide.

Having filled several balloons with CO2 we experimented with its weight (CO2 is heavier than normal air) and its ability to support combustion (it can’t).  We lit candles and poured our CO2 gas onto the flame, which was quickly extinguished.


Our next experiment required a bit more attention to safety.  We headed back out to the workshop and combined Hydrochloric Acid with Aluminium (Foil).  After a couple of minutes waiting for the acid to eat through the oxide coating on the foil we were rewarded with an exothermic reaction resulting in Aluminium Chloride and a small amount of Hydrogen.  Hydrogen is quite flammable and as we discovered makes a delightful pop sound when a small amount of it encounters a lit match.  Much fun had!

Finally, having learnt about atoms, molecules and chemical reactions we were in a position to talk about the chemistry involved in our project.  First - in our concrete (which has 6 active ingredients, all of which react with water in rather complicated ways) and secondly in our plant.  We learnt about the reaction that happens during photosynthesis and the joy of having billions of plants around the world generating O2 for us to breathe.  We even had one on hand, setup to show how much Oxygen it had produced that day.

Awesome stuff!


PS, I apologise for using the American spelling of ‘Mould’ for the last couple of blog posts.  Hopefully not too many people were put out by my use of ‘Mold’.