Science Experiment Question.?

Question

Today in my science class my teacher did a small lab and then asked us a question about it. What he did was put a small amount of rubbing alcohol in an empty water jug then he rotated the jug forward to backward in a circular motion while the jug was horizontal while covering the opening of the container. Then he proceeded to light a match and put it in. After this a large spark appeared in the container and then quickly dissipated. He then repeated the experiment only to find out that the spark did not reoccur. His question was: Why didn't the alcohol spark this time? I was thinking it was because the oxygen had been burned out of the container and filled with something else.

Answer 1

i think you thought right!!!. due to the depletion of 02 in the container combustion did not take place as a result the sparks did not reoccur.

regards and hope it helped

Answer 2

Very good thinking!  Air is only 20% O2.  If the O2 really went away, more air would be drawn into the jug and there would probably be a flame the second time.  WHat is actually happening is that flame reacts alcohol with oxygen creating different gases (if you have had chemistry, you could make some good guesses at what those gases will be).  Because those gases take up about the same volume as the O2, there is no fresh O2 drawn in.  In fact, because the gases have been heated by the combustion, the net change in volume is probably positive so air is prevented for coming in because N2 (~78% of air) and the products of combusion are blowing out of the jug.  Science rules