How Calcium Carbide forms Acetylene, to blow out a pumpkin’s face
According to Wikipedia:
The reaction of calcium carbide with water, producing acetylene and calcium hydroxide, was discovered by Friedrich Wöhler in 1862.
CaC2 + 2 H2O -> C2H2 + Ca(OH)2
[Calcium Carbide + 2 water -> acetylene + calcium hydroxide (the latter being non-flammable hydrated lime, also called slaked lime)]Source: Calcium Carbide
This reaction was the basis of the industrial manufacture of acetylene, and is the major industrial use of calcium carbide.
Acetylene is used as a fuel for use with a blow torch in melting metal and welding.
We saw in Grant Thompson’s video that calcium carbide looks like a form of rock salt, except that it has a dark color due to impurities. Pure calcium carbide is said to be a colorless solid.
It is quite possible to make your own calcium carbide, as shown in this video: Make Calcium Carbide.
Because the acetylene gas released by adding water to calcium carbide is flammable, all Thompson had to do to make his pumpkin face blow out was to place a very small amount of calcium carbide in a cup inside the pumpkin, add water to start the release of gas, close the pumpkin, add a fuse through a small hole, light the fuse, and quickly step away.
Safety precautions used by Thompson include the small amount of calcium carbide (about a tablespoon, it appears), placing the pumpkin out of doors, and especially stepping out of range of the small explosion.
The acetylene gas is compressed inside the pumpkin, but expands in an explosive manner when sparked by the lit fuse.
A great article about the early development and use of the acetylene-making process is found here.
