Exploding Acetylene Pumpkins! Halloween Science

Exploding Acetylene Pumpkins! Halloween Science


Hi, it’s Halloween. We’re the Ri.
So we’re exploding pumpkins. This year for our explosions we are going
to be using this compound – calcium carbide. It reacts with water, fizzing away producing
lots of gas and that gas is acetylene, which you may know
is very flammable. We send the gas along the tube, filling our
pumpkin with acetylene. When it’s ready, we can light the fuse, ignite
the acetylene, blowing the face out of our pumpkin. Calcium carbide is made of calcium ions and
carbide ions. Carbide ions are two carbons bonded together. And it’s these carbon atoms that are joining
with our hydrogen atoms from the water to give us a hydrocarbon, in this case acetylene. Like other hydrocarbons, like petrol,
it’s a really great fuel, burns really well and will give us an awesome explosion to power
our pumpkins. We’ve been blowing pumpkins up all day, but
not all of them have blown up. In fact some of our pumpkins only showed a
small amount of combustion. And our theory is that these particular pumpkins
had so much acetylene inside of them that there really wasn’t much oxygen for them
to burn with. Of course we need oxygen to get a good explosion
and without it we’re going to get incomplete combustion. Another sign of this is the black soot and
smoke we can see coming out of this particular pumpkin. We’ve been collecting and burning loads of
acetylene at once to get an explosion, but in the early 1900s, miners used a more
controlled version of this reaction to power their headlamps – carbide lamps. They would have a rock of calcium carbide
in them and a small valve to drip water onto it slowly and steadily, producing a constant
stream of acetylene that they could light to see their way around
the mine. Thanks for watching. If you’ve got any ideas
how we should explode pumpkins next year, let us
know in the comments. Don’t forget to like and subscribe to the
channel, and happy halloween!

24 thoughts on “Exploding Acetylene Pumpkins! Halloween Science

  1. I suggest supplying the pumpkin with a stream of oxygen on one end of the pumpkin via the decomposition of hydrogen peroxide and acetylene on the other to prevent incomplete combustion

  2. Some ideas for next year. KNo3. Liquid oxygen that flows visible gas vapor out of the pumpkin and then ignited. Petrol. Vibration sensitive Nitrocellulose. Would love to see any of these next year.

  3. Oxyacetylene, as mentioned by some, would be interesting as an experiment but probably far too violent for carving. Do your first tests outside.
    Oxygen+dust could be cool, if it could be done reliably. Sawdust, metal powder, flour, pollen etc.
    Electrolysis of pumpkin juice and the explosion of the resulting H2+O2 would be cool.

  4. paint inside with damp NI3. Dry out. toss tennis balls at it from across the room.
    I also think thermobarics could be interesting – something relatively inert in a mass, but volatile when aerosolised.

  5. As a child in the 50s, I can remember that a few neighbours still used carbide cycle lamps, & a lump of carbide & a splash of water in an old paint-can makes a loud banger! 😀

  6. Before widespread rural electrification, some houses had 'carbide generators' to fuel gas lights. Growing up, I lived in a house that still had the generator below ground in the back of the house and much of the gas plumbing for the lights still intact within the walls.

  7. For next year: given the fuel mixing difficulties, maybe try electrolysis of water to get a perfectly balanced hydrogen/oxygen mix?

  8. During the early 1900-dreds they used is also as head lights on bikes all around Europe.
    There is also this tradition in rural parts of the Netherlands to fire the lids of big milk containers with carbide. They can reach over 100 meters.

  9. We watched Dan give one of the best demos at the Science Museum Wonderlab last weekend. Dry ice and then liquid nitrogen with gummy snakes. Absolutely brilliant. “Be prepared to run if I spill any.” Loved this explanation of making acetylene.

  10. I had great fun teaching my friends sons about balanced equations and gas laws on bonfire nights. Fireworks were much less fun than a collection of 2 litre plastic bottles, a bucket of water and cylinders of oxygen and acetylene. Work out the ratio of oxygen to acetylene giving a perfect balance, explain that 1 mole of oxygen occupies the same volume as 1 mole of acetylene at constant temperature and pressure, fill the pop bottle with the appropriate ratios of gases, pop the lid on and then throw the bottle on the bonfire.

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