[INTRO MUSIC PLAYING]
Hi everyone welcome back to Cody's Lab.
So Today Im going to show you something that I discovered back when I was thirteen years old.
Or, I should say, "rediscovered", because; I did some research on this later on
and found that Michael Faraday had discovered this about a hundred years before I was born.
But, I also noticed that there was very few videos of it on YouTube.
And so, I thought, I would make one.
So, today I'm going to show you some gunpowder.
So... [To the camera operator: Can you go down onto the block]... so, I take some gunpowder here.
This is black powder, the old fashioned stuff.
None of that fancy-smancy smokeless.
And you see... take this... touch a flame to it.
And it instantly explodes, and produced lots of smoke.
Now, if I were to take a little cup here and fill it...
...most of the way up with gunpowder. Light a stick on fire and stick it in there...
... it would be an extremely bad idea. Right?
Given that the flame temperature of burning wood is nearly 2000 degrees Celsius...
... and the ignition temperature of gunpowder is about 200 degrees Celsius...
Make your predictions now.
So, lets make sure my gunpowder is shut and moved away.
Im going to light this wood on fire and stick it in there.
So you can see that the wood is burning
And you can see that the fire was instantly put out, when I stuck the stick into the gunpowder here.
Let's try this again...
Light the wood on fire. As you can see it is burning.
And as you can see, the gunpowder was not set off.
Now, I don't really want to light this much gunpowder off all at once...
... so let's just have a smaller amount here.
If I light the stick again... blow it out... and then touch it to the gunpowder. You can see it ignites...
... Quite spectacularly.
Let's do this again...
Let's actually... Let's do a little bit larger pile.
Let's actually start with the flaming stick.
Okay, stick flaming... stick it in there... you can see the gunpowder put it out.
Now, try this again...
... get the stick burning, blow it out, and it ignites.
Now, when I was thirteen years old this blew my mind! The stick, on fire, going into the gunpowder, did not ignite it...
... but I could take the stick, blow the fire out, and then shove the hot coal into the fire [He meant gunpowder] and it would ignite the gunpowder.
Now, the flaming coal there thats only like 800-something degrees.
The glowing red-hot temperature. And the fire is hotter... So what's going on?
Well, as it turns out, and what Michael Faraday described, is that the flame...
... though being very hot, is very diffuse. It's a very low density plasma. It doesn't have enough thermal mass...
... to transfer enough heat to ignite the gunpowder particles.
Another thing that keeps the flame from igniting the gunpowder is the fact that flames are actually hollow.
Especially when you have candle flames, or something similar.
Because the combustion is actually causing hot flammable gasses to be produced from the wick or the wood...
... which react with the oxygen, they only do so at the edge. The oxygen is only on the outside of where the gas is mixing.
So the flame is actually hollow.
My blowtorch flame, of course, is completely solid. Which is why it's able to ignite the gunpowder.
Because it's much more of a solid, more powerful flame.
Because the flame cannot transfer enough heat ignite the gunpowder grains.
I may as well be sticking the stick into some sand. As you know sand is very good at smothering fires.
Because it's very hard for the oxygen to get down through the sand grains to continue the combustion process.
Now you may ask, what happens if I extinguish the wood, pull it out, and stick it back in?
Okay, fire... pull it out, stick it back in.
And as you can see, the gunpowder did not ignite here.
That's because the act of blowing it out changes the fire from being a cloud of gas burning...
... into a hot coal in the center that is burning.
You see when it goes into the gunpowder it extinguishes the whole fire. Everything is put out, there is no oxygen.
But, when I blow it out, the hot carbon in the center ignites.
And when you got the carbon burning, the carbon is a solid material, and so it's much more able to transfer its heat.
But, of course, when it's in here and then I pull it back out...
I have caused everything to cool off too much for the ignition to be possible.
Now, a lot of you are probably asking, well, what about smokeless powder?
Well, let's find out, shall we?
So, there's my smokeless powder... this is a nitrocellulose based mixture.
So, it's not quite the same as the black powder.
Let's see what happens here.
I'm going to light my stick on fire.
Look at that! It also works.
I actually did not expect that. [LAUGHS]
So, it does work with smokeless powder as well.
Although smokeless powder should be a little bit more easily ignited...
...since you don't have to worry about having to melt the potassium nitrate.
And there you go.
I sort of roll my eyes when somebody tells me that a candle burns at 3000 degrees.
Yes, the candle's flame is technically 3000 degrees, but you're never going to melt a piece of platinum in a candle flame...
... unless the platinum is incredibly thin. It's because it just can't transfer enough heat to it, before the heat gets conducted away or whatnot.
Anyway... Hope you enjoyed, I'll see you next time.
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