Friday, February 24, 2017

Chemistry Final

Not a Chemistry final like an exam, more like a combined last class on applied Chemistry. 

We looked at how the breaking of chemical bonds absorbs energy by making chocolate ice cream (salt as it dissolves breaks into ions, further cooling the ice).

We looked at acid base interactions by making bath bombs (baking soda and citric acid do  not react until you add water).

We ended up with a side lesson on diffusion as the essential oils made the whole house smell like sandalwood, rosemary and orange!

We did a little physics with tea bag rockets (convection currents, fire as a chemical reaction, density).

And we did a little organic chemistry with candy making.

The changes in the sugar which take candy from being a solution (liquid at room temperature) to firm ball (squishy) to hard crack (brittle solid) are neither phase changes nor chemical reactions.  They are the result of heat producing changes to the shape of the sugar molecule!

Sugar in the solution and in the lollipop have the same chemical formula (C6H12O6), but different molecular structures!

Fascinating and delicious!
 We also heated and cooled sodium acetate ("hot ice").  This is the stuff in reusable hand warmers: they are a super saturated solution of sodium acetate that, when disturbed, comes out of solution into crystals, releasing heat. 

You can reheat them by boiling to return them to a liquid state, essentially storing that heat to be released later. 

I gave the kids sodium acetate hand warmers as a memento of the class.

We ate the ice cream and a king cake, and celebrated Chemistry.

And they took home their (cleaned) aprons, notebooks, lollipops, bath bombs, and we are done!

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