Thursday, March 3, 2011

Surprise Fire

In science right now, we are studying physical and chemical changes. Today we did a lab to introduce a lot of the concepts we will be talking about, as well as to review lab safety procedures. Like a good little teacher, I decided it prudent to test out the lab prior to the students coming in to make sure it, you know, worked.

This experiment is called, "Surprise Fire." If you mix these two chemicals together (potassium permanganate and glycerine) they are supposed to react and spontaneously combust. Key word: supposed.

Unfortunately, I wasn't able to get into the room where the chemicals are stored until about 15 minutes before school started. I wasn't worried, though, because the reaction was supposed to occur within 20-60 seconds. So I donned my safety goggles, poured out a silver dollar size pile of potassium permanganate, dabbled in a bit of glycerine, and waited. And waited. Nothing happened.

Another teacher came by to ask me a question. I went to talk to her while keeping the corner of my eye on the table where the chemicals were sitting. Nothing happened.

The vice principal came in to see how I was doing and if I needed any help with anything. I told him I was fine unless he knew how to make a couple of dangerous chemicals react with each other and catch on fire. Meanwhile, another teacher from my team came by. Apparently she had also had trouble with this lab when she did it. It also would not combust while for her, so she tried to wipe it up with a paper towel, giving it up as a bad job. Her students were disappointed (this was during class), but whatevs. But then! The paper towel caught on fire! And she dropped it on the ground.

So now all three of us were at a loss. We didn't know what to do. We didn't want to just throw it out, cause what if it caught fire in the trash can. Joe (the VP) tried to wipe it up with a damp paper towel, thinking maybe the friction would get things going. No luck. By now the bell has long since rung and I am supposed to have picked up my students from outside. But I didn't want to just leave it there. What if it burned down my classroom?!

Deciding that since it had been almost twenty minutes since I had started this experiment, I deemed it allowable to get my class. A couple of students were waiting outside my door, hoping to go in before everyone else showed up. I told them, rather forcefully, to "Wait. There." and "Do NOT go in the classroom." Then I hightailed it to the outside and get the rest of my kids.

When we got back to my door, I gave them the following instructions: "When I open this door, you are to go straight to your desks, pull out your journals, and start writing. Do NOT touch ANYTHING."

Of course none of them listened to me and they all immediately gathered 'round the back table where the experiment was set up. No respect. How a pie tin containing a small pile of wet purpleish flakes attracts some much attention from 10-year-olds, I'll never know. I successfully shooed some of them away and then sat down to tackle the problem at hand.

I figured the best problem would be to get the chemicals to react so that I didn't have to worry about it catching on fire in the garbage. This is an elementary school. There's lots of paper in there. Poking it with a wet paper towel didn't work, but I certainly didn't want to prod it with a dry one. What if my hand caught fire?!

Well, hows about a half wet half dry paper towel? I carefully scooped up a bit of the mixture with the towel, dropped it on the tin, and hightailed it out of there. Well, to the other side of the classroom, anyway. Then... it happened. The towel started smoking and then - BAM - a two-inch flame licked it's way up the towel. Sure, it wasn't the foot-high flame the lab book promised me, but it was fire! The chemicals reacted!

Like to smartie that I am, I decided to go ahead with the lab as planned. The main point was about safety, right? I could still teach that, right? Right.

So I set it all up to the T. I thought that maybe I was too generous with the glycerine and that it overwhelmed the potassium permanganate or something. The set up was absolutely perfect. But... nothing happened. My students were all disappointed, of course. Most of them caught the tail end of the paper towel burning earlier and were ready for more action. While they all sat there staring at the boring pile of non-combusting chemicals, I explained what was supposed to happen and why.

Then I said, "Now. We will be doing a lot of experiments throughout this unit. Some of them are dangerous. So you must follow the procedure EXACTLY. If I see ANY of you doing ANYthing that is not in your lab book, you will not do ANY more labs in my classroom. Ever. EVER. That being said, I am going to do something that would be an absolute no no if any of you were to do it. But I can. Because I'm the teacher." And I picked up a pencil and poked the chemicals with the eraser.

They started smoking. And then they caught fire. The class all cheered and then gagged cause it was stinky. I sent them all to fill out their lab sheets, cleaned up the ashes, and we were done.


1 comment:

elsalgal said...

Today we did chemical reactions in a zip bag. It was a big hit. Especially the bags that popped open explosively. Even one of mine.

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