step into my classroom: volcanoes

This morning was one of those "the things I do for my kids" moments.

My first period earth science class is learning about volcanoes, and today I did a demo to model the fact that magma has a lower density than solid rock, which is why it forces itself up to the surface and forms volcanoes. I used cooking oil to represent the magma, and water tinted blue to represent the rock. I poured oil into the water, where it formed big bubbles of oil that worked their way up to the surface. The students oohed and aahed, and I stirred the two liquids to show that their densities would still cause them to separate.

At this point, the wheels began turning in their heads. I hadn't intended for this next part to happen, but I love when the students make their own inquiries so I allowed them to go "off track" for a few minutes. Our conversation went something like this:

Student A: So, if you had a straw, could you drink the water underneath the layer of oil?
Student B: Well, when you put the straw in, it would go through the oil so there would still be oil in the straw.
Student C: But if you blow through the straw then you could push the oil out!
Me: Yeah, actually that would probably work. I just wish I had a straw so we could test it.
Student D, E, F, etc: You DO have a straw! Right there!

They pointed to my hot pink straw, which was chillin' in a cup of iced coffee. Of course.

All students: Drink it! Drink it! Drink it! Drink it!
Me: OK!! ... Wait, really? Do I have to?
All students: YES!!!

Now here is where some of you are probably thinking, "Of course you don't have to drink it! You're the teacher! Don't listen to them!" But, there are times for spontaneity, and at this point I had everyone's rapt attention so I went for it.

I put my straw into the beaker.
Blew bubbles to expel the oil from the straw, extracting giggles from several students.
And then, after a moment's hesitation, took the tiniest sip.
I paused for dramatic effect.
Smacked my lips as if pondering the flavor in my mouth.
Students laughed.
Then I took another huge sip and they waited with bated breath to see how I would react.

Me: Alright, it is possible to drink the water!
Students: *cheers*

Then I withdrew the straw from the beaker and promptly returned it to my coffee.

The things I do for my kids...