First of all, calcium carbide is calcium carbide, CaCz+2HzO=Ca(OH)z+CzHz↑ After this reaction, when reacting in a test tube or conical flask, use a plug with a catheter to react and ignite it, which can prevent the explosive gas mixed with acetylene and air from being ignited at the initial stage of the reaction and be dangerous. Acetylene is flammable if it can be ignited.

Of course, if we think rationally, we should directly replace the reaction with acetylene gas, which can be understood as other substances generated by the reaction. Because of our fixed thinking, calcium carbide and water generate acetylene, so we use this reaction to ignite the generated gas to verify that acetylene is flammable. When studying, students should cultivate dialectics and consider more things.

But for the exam, what I just said is a dead end.