30 November 2012

"It's fricking blowing my mind"

My Honors Chemistry class is just starting to learn about the mole.  For HW (the first one I have given since September) they had to watch the following TED video:

While it doesn't teach them how to use the mole, it got them really excited to learn about how to use it in chemistry.  I started the class with a DO NOW
What, in your every day lives, could be expressed in terms of moles?
I gave them a chance to consider it and then discuss with their groups.  We got some really good answers like sand on the Jersey shore, Doritos, and hair on a human head.  I let them figure out how to calculate hairs on someone's head (someone used their iPhone to Google how many hairs are on a human head.  FYI 90,000-150,000) and we figure it is somewhere in the range of 9x10^-24; they decided that it was not at all useful for every day things.

Then the questions started.
"What if we added up all the hairs on every human head on the planet?"
"What if we added body hair?"
"Eyelashes?"

Someone grabbed a computer and started Googling and found that if you added up all of the cells in every human on the planet, you would only have about half a mole.

The mole is still not useful because the numbers are still unbelievably small.  So then I pull out 1 mole of water (18mL) which is about the amount that fits in the palm of your hand.  

One girl says, "Wait. That's 1 mole? You mean that small amount of water is the same as if we covered the Earth in 5 miles of donuts?! This is fricking blowing my mind!!"

I love it when it clicks.