Wednesday, June 8, 2016

Homeschool STEM: Adventures in Potassium Nitrate and Sugar

First of all: nope, no weekly work plans again this week! Syd's in a pretty intense ballet program for a couple of weeks, so so I'm only doing school with Will, and I can make her work plans up on the fly each morning. Since I don't want to cover any subject that she and Syd usually do together, I mostly have her doing our daily stuff, but this is also a great time for us to work on the projects that she alone especially likes. For instance, today she has a Math Mammoth lesson, cursive practice, her Wordly Wise, some assigned reading, at least 300 words of writing for her "novel," and she and I are going to play some more with rocket candy, ie. potassium nitrate and sugar.

Will first got really into explosives engineering back when I organized a STEM Fair for our homeschool group; while Syd built a table for her project, Will wanted to study explosives for hers. Sure, we did the old Mentos and soda trick, and reviewed the exothermic reaction that occurs when you decompose hydrogen peroxide, but I knew what she really wanted, and so that's why we found ourselves out on the driveway numerous times that spring, testing various homemade rocket fuel recipes.

You'll probably be horrified to learn that homemade explosives are actually super easy to make; all you really need are potassium nitrate, sugar, and a container. To make better explosives, add in a temperature-controlled outdoor heating source. To make fancy explosives, add in a few standard, easily obtained additives.

Regular table sugar is the fuel for this explosive, I am told--Will and I are both starting from scratch here, learning together, and although I'm figuring out the science involved, and so is she, of course, for now we're mainly relying on various online tutorials and explanations, repeating the demonstrations that we've seen to try to get the same results, making notes of what variables we want to change when we're confident enough to experiment, etc.--that sugar is the fuel, and that you can grind or melt the sugar to let it interact better with the potassium nitrate, but for the purposes of creating a workable fuse, you don't have to. Sugar actually has a pretty complicated molecular structure with lots of nice hydrogen and oxygen to make a nice, big exothermic reaction.

Potassium nitrate is simpler to model. Also note, on this spec sheet, the important information that it can combust with prolonged exposure to heat. I do have plans to buy an outdoor griddle for the purpose of making a better-mixed, more stable mixture of potassium nitrate and sugar, and so this tells me that when I do, I have to be very, very, very careful.

We're not using any heat in this first combination, however, in which we're simply following this simple tutorial to make a fuse:

Despite the risk of giving you too much information about my misspent youth, I'll tell you that this part is exactly like rolling a joint:

And it's easy enough for an eleven-year-old to do completely independently:

Again, it's not the most efficient fuse, nor the most elegant, but it DOES work...IF you can get the lighter lit!

Okay, here's what it actually looks like in action:

Yeah... we're still working on a reliable recipe for that smoke bomb.

We've played with this fuse several more times--in a couple of different smoke bomb recipes, and for the merriment of burning things safely in the middle of our driveway (a crumbled up sheet of newspaper with more potassium nitrate and sugar inside makes for quite a jolly show!)--and it's dependable. It always works, and hasn't yet ever flared up or done anything unexpected. It's extremely fragile, however, so when we get to the making of actual model rockets, we'll definitely need to try a more sophisticated type.

I know some of you (many of you? Most of you?) are thinking that I'm crazy right about now, and that's totes fine. I'm pretty sure that my sanity is cracking quite often, actually. But here's the thing: what's the point in homeschooling if you can't let a kid follow her passions? You've got it easy if your kid is passionate about drawing or dinosaurs. You have to really figure out what it means to you to let a kid follow her passions if she's into something not so easy. One of my mom friends let her kid watch homebirth videos on YouTube when she was little--tons of homebirth videos!--because that's what the kid was interested in. Will she become a midwife or an obstetrician when she grows up? Who cares! Maybe she'll just grow up with an excellent knowledge of reproductive anatomy and will walk into her own childbirth experiences, if she has them, amply prepared with appropriate expectations. The important thing is that she got to immerse herself in what interested her, and nobody got to shame her or tell her that it was weird.

Will my kid grow up to be a rocket engineer or a fireworks designer? It doesn't matter to me. All I care about is that she wants to learn about explosions, and so we're learning about explosions. Maybe she'll just grow up with an excellent knowledge of exothermic reactions, and the ability to build a homemade toilet paper fuse should she ever need to. Doesn't matter to me. What does matter is this: chemistry, physics, fine motor skills, research, risk management, molecular modeling, recipe following, experimentation--seems like a fine way to wrap up sixth grade, to me!

No comments: