All I Know Is One Time In Chemistry My Lab Partner Tried To Set Me On Fire

I forgot this other fun little teaching science tidbit:

For two weeks, I only taught what the science IST gave me, basically test prep books. It was like death. Sooooo boring. So, I ended up looking up a simple science experiment and doing that. It was fun. I asked the Science IST if she had any other experiments I could do instead of the terrible test prep books.
She says sure. She brings me a whole crap load of stuff. We are going to see how many drops of water can fit on a penny. (It's cool, the kids guess like 10, but you can really fit like 60-70.) So she gives me all the supplies. I say, "Okay, cool, but what is the purpose?"
Her: You....are....putting...drops...on.....a....penny.
Me: Right. But what is the point of the experiment?
Her: Okay, here is the dropper, and here is the penny....
Me: I Know!! But after we finish the experiment, I say...? I don't know what concept I am teaching here.
Her: Miss Vinson, you obviously didn't pay attention in high school. *Starts to leave*
Me: What the...? Can you tell me what I'm teaching?!
Her: *sigh*, I have been doing you A LOT of favors lately.
Me: Thanks?
Her: it is about surface tension and cohesion.
Me: Cohesion?
Her: *Sigh*