Exploding coffee tin experiment.
Discussion
Anyone do this at school at the beginning of the 70s.
Empty catering tin of instant coffee. Hole in base and lid, stand tin on lid. Gas from bunsen burner fed into bottom hole, bunsen removed and top hole lit.
It'd burn for a short time drawing air in though bottom hole, when gas and air reached the critical mixture the thing would explode, and hit the ceiling. We had a chemistry teacher who'd repeat this many times, each lesson.
His rationale was that once the area converted from coal gas to natural gas it wouldn't work. If he told us why then I've forgotten, anyone know?
Empty catering tin of instant coffee. Hole in base and lid, stand tin on lid. Gas from bunsen burner fed into bottom hole, bunsen removed and top hole lit.
It'd burn for a short time drawing air in though bottom hole, when gas and air reached the critical mixture the thing would explode, and hit the ceiling. We had a chemistry teacher who'd repeat this many times, each lesson.
His rationale was that once the area converted from coal gas to natural gas it wouldn't work. If he told us why then I've forgotten, anyone know?
No reason why it wouldn’t work with natural gas in my view.
Coal gas is what? H2, CO i expect, methane, ethene and some other gaseous hydrocarbons?
I think the only effects would be the point at which it all burns rapidly and the energy released by that rapid combustion (depending on the amount of CO in the coal gas, I’d expect natural gas to be more energetic because its not partially oxidised.
Coal gas is what? H2, CO i expect, methane, ethene and some other gaseous hydrocarbons?
I think the only effects would be the point at which it all burns rapidly and the energy released by that rapid combustion (depending on the amount of CO in the coal gas, I’d expect natural gas to be more energetic because its not partially oxidised.
We used to do this: https://www.techknow.org.uk/wiki/index.php?title=D...
I can't see that being done at school anymore.
I can't see that being done at school anymore.
Mabbs9 said:
We did powder explosions. Custard tin, apt for this forum, a hole in it for attaching a bike pump. Candle lit inside. Custard on spoon next to pump outlet. Lid on tight, one hard pump. Boom.
It was custard powder for us in Chemistry too- a practical example of a dust induced fuel-air explosion. ‘Flash, bang’ experiments really got us engaged back then, it’s a crying shame if health and safety takes away that from current generations.darren f said:
Mabbs9 said:
We did powder explosions. Custard tin, apt for this forum, a hole in it for attaching a bike pump. Candle lit inside. Custard on spoon next to pump outlet. Lid on tight, one hard pump. Boom.
It was custard powder for us in Chemistry too- a practical example of a dust induced fuel-air explosion. ‘Flash, bang’ experiments really got us engaged back then, it’s a crying shame if health and safety takes away that from current generations.Mabbs9 said:
We did powder explosions. Custard tin, apt for this forum, a hole in it for attaching a bike pump. Candle lit inside. Custard on spoon next to pump outlet. Lid on tight, one hard pump. Boom.
Yep - we got this one in the earlier 2000s, probably banned now. Same teacher (who was brilliant) also did all sorts of cool stuff with explosions, electricity and we accidentally made too much chlorine gas once and had to leave the room for a bit 
He retired after our year, I suspect the current generation of teachers won’t go beyond the textbook as he did.
It was a cocoa tin with us, IIRC. The point of the experiment was to demonstrate how the Davy lamp prevented mine explosions when being mines were still being lit with a naked flame. As soon the experiment was repeated with a sheet of metal gauze over the hole the explosion no longer happened, which of course is the principle the Davy lamp operated on.
https://en.wikipedia.org/wiki/Davy_lamp
https://en.wikipedia.org/wiki/Davy_lamp
23.7 said:
I've wondering how to get rid of all those old paint tins the council won't take.
Ive been trying to find some cheap oil drums - https://www.youtube.com/watch?v=Bczn_1S8SYoI have calcium carbide but its a bugger to get the air /acetylene ratio correct...
Reminds me of my school days in the 60s. Sodium chlorate/weed killer and sugar. Eventually we got into some serious trouble after blowing up the school drainpipe, big holes in cliffs and.. burning down the apple tree in our garden causing a visit from the fire brigade and the police. And that was then end of my bomb making days. After that I wacked a couple of 303 shell in a vice and narrowly missed my toes.
Then my mother had a nervous breakdown and life changed. I don't think that it was me that caused it...
Then my mother had a nervous breakdown and life changed. I don't think that it was me that caused it...
nute said:
Ive been trying to find some cheap oil drums - https://www.youtube.com/watch?v=Bczn_1S8SYo
I have calcium carbide but its a bugger to get the air /acetylene ratio correct...
Oh Jesus, that's funny...I have calcium carbide but its a bugger to get the air /acetylene ratio correct...
When I was doing my A level Chemistry is ~2002, there was only 2 of us in our class. 1 lesson we'd done what we needed to do, with 10-15 mins left. Our teacher, who at the time was only about 30, disappeared into the cupboard and came back with an old flat coffee tin with a hole in the top. The rest is as the story above. That would have been firmly into the natural gas era, and the way the lip shot up in the air, it definitely still works.
It doesn't work with natural gas.
Coal ("town") gas is lighter than air, so rises through the top hole in the can, drawing air in through the bottom hole until, as you say, there's an explosive mixture.
Natural gas is heavier than air and falls out of the bottom hole in the can, so there's nothing to light at the top hole.
Coal ("town") gas is lighter than air, so rises through the top hole in the can, drawing air in through the bottom hole until, as you say, there's an explosive mixture.
Natural gas is heavier than air and falls out of the bottom hole in the can, so there's nothing to light at the top hole.
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