How does #"calcium carbide"# react with #"water"#?
Well it is simply an acid base reaction.
This reaction used to be the basis of the old miners' lamp. A miner would take a lump of the carbide, moisten it with a bit of water, stick it in a lantern on his helmet, and light the acetylene gas evolved to provide illumination.
Of course, the naked flame constituted a very significant safety hazard underground, in that combustible gas in the mine or the cave would ignite. Later versions enclosed the flame in gauze.