Chocolate chip cookies and Penny Chemistry

     Today has been a chemistry day: we have baked chocolate chip/ walnut cookies and have observed how the addition of ingredients changed the nature of the mix. (The boys volunteered to 'test' each stage -- Laugh). The gradual addition of more and more flour (Four cups in all) resulted in the dough getting harder and harder to mix -- and lead to bits falling away. Then we observed how the addition of heat affected the mix. (And again, they offered to test the results.) A more complete discussion -- and one that will be recorded in our Chemistry notebooks can be found here: Cookie Chemistry and here: Cookie Chem. Each of these articles allows for this particular Chemistry lesson to be extended over days if not weeks.
     While the cookies were cooling, we set to work on American History. I had conceived the idea of teaching American History through coins (Numismatics) and stamps (Philately) when my youngest son demonstrated an overweening interest in the subjects. Today we pulled out our biggest jar of coins and, after separating the pennies out, began sorting them by decade. But we ran into a little problem: many of the dates were hard to read because the pennies were so dark. Chemistry op! We looked up the recipe for cleaning pennies and found this: Chemistry fun with pennies and Cleaning Pennies. After digging out the necessary ingredients, we started measuring. This also offered an opportunity to practice multiplication and fractions. I asked 'If we want to make 4 times the amount called for, how much of each ingredient will we need?' When they had figured that out, I asked -- and if I only have a 1/4 tsp measure and a 1/4 cup measure, how many of each will I need?' Satisfied that they had the right proportions, they added the ingredients. Mixing carefully, they observed the change in the liquid as the salt went into solution.
      The cleaning solution ready, the boys carefully added the pile of pennies and mixed. They stood watching for a long time then decided to let time do its work while they went off to other projects (in this case, cleaning their rooms). When the pennies were sufficiently clean, they carefully poured the liquid through a plastic colander into a plastic bowl, in preparation for the next Chemistry experiment: Instant Vedigris and Copper plated nails.  Leaving the selected pennies to oxidize and the nails to soak, they returned to the penny sorting operation. It will be interesting to see what decades my penny box represents!