How do I keep hydrogen or oxygen in a test tube when pulling them out of water? I have a Styrofoam cup with two metal thumbtacks pushed though the bottom, and about 100 ml of distilled water mixed with 6 grams of sodium hydroxide in the cup. The cup is sitting on a 9 volt battery which separates the hydrogen and oxygen in the cup through the thumbtacks.
I put a test tube over the thumbtack that is producing oxygen and one over the thumbtack producing hydrogen. I'm trying to capture the hydrogen and oxygen in the test tubes and light them on fire. My problem is that when I pull out the test tube, the little water left in the tube pulls out all the gas when it falls out. How do I keep that from happening?