Thursday, March 17, 2011

Penny Cleaning


Lil Muallimah's penny pinching and penny polishing not only got Lil Muallim # 2 excited but Lil muallim # 1 as well. He not only played with those activities but wanted something VERY his level.

I immediately googled somthings out and our chemistry lesson was underway.

I found the following resources to be very helpful, from American Chemical Society and Spark Lab 

Using the guidelines from the above two activities we worked out our own:

Fact # 1  Pennies are not entirely copper they can be made of zinc/steel with a copper plating. The hsitory of pennies can be studied on Wikipedia

Step 1: Lil Muallim + 3 (and 2) brain stormed what liquids they wanted to experiment with, to try and polish a copper coin. Heres what we came up with. We used old jam jar lids as petri dishes. :)

They wanted to try fresh grapefruit juice, apple juice, orange juice (not store bought juices), milk, vinegar, water, soya sauce, maple syrup, oil and gasoline (left over Baba's Traxxas buggy)

They made their own hypothesis for each liquid, whether it would work or not. To find out Lil Muallim # 1 picked out each coin one by one and scrubbed it with an ear bud.

As he cleaned each coin he placed it next to the lid it came from,  with the ear bud showing the residue on it.

Their hypothesis proved correct in mosts cases.

partially clean: grapefruit juice, apple juice, orange juice, milk and vinegar

No difference with: water, soya sauce, maple syrup, oil and gasoline (it was out of nitro, Lil Muallim # 1 wondered if that was the reason) 

Generally speaking with this activity they did not actually polish a penny but were able to rub the tarnish off some of the coins

I found a good explanation of what works and what does not specially WHY, for  example:

You are not really "cleaning" the pennies, you are dissolving the copper oxide "tarnish" on them, allowing it to wash away, exposing the underlying copper metal. This is important to note because things that are good at removing soils, like soap, detergent, and shampoo will be of no use in dissolving the copper tarnish. But some things that are poor cleaners like lemon juice plus salt (a mild acid), vinegar plus salt (a mild acid), and Coke & Pepsi (mild acids) will be good at removing the tarnish.
6. The acidity of the juice has a bit to do with it, but salt has a bigger effect. You can "clean" a penny a little bit and very slowly with lemon juice or vinegar (mild acids), but put a dash of salt in the lemon juice and the penny will turn orange with a quick rub. People say that ketchup and taco sauce are good cleaners for pennies, but read the ingredients: "Tomatoes, Vinegar, Salt . . . "
 read these and other explanations here.

Another experiment with pennies coming soon!

1 comment:

jmommymom said...

This is a fun experiment and very useful too. I will show my son so to help him decide how to clean his coins.


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