Y do chemical changes occur when piece of zinc is in hydrochloric acid & a piece of burning splint is over it?

The oxidatiion potential of Zn is such that it is above H in the electromotive series. Hydrogen is flammable in air.

Zn + 2HCl ===> ZnCl2 + H2

2H2 + O2 ===> 2H2O

Do you know what the funny thing is....i did this lab like 3 days ago in the Putting it together lab thing. Ok well this is what happens. Zinc and Hydrochloric acid reacts together and has a single displacement reaction. This occurs because in the activity series (pg 20 of ur course pack if its the same) zinc can displace hydrogen. And since zinc displaces hydrogen, instead of zinc + hydrochloric acid, it's Hydrogen + Zinc Chloride. Now that hydrogen is out they want you to test if its there. You put ur finger over the tube because they want to give the zinc more time to react and they dont want the hydrogen to escape out of the tube. Now you test if there is hydrogen. This is by simply sticking a burning splint inside. and....POP!!! there is hydrogen!! check ur text boook for more understanding.

balanced Formula is
Zn + 2HCl H2 + ZnCl2