Question on Hydrogen Balloon I tried to extract hydrogen for my kid's birthday, by mixing caustic soda with water and aluminum foil (mixed in a glass bottle). A lot of heat and (hopefully)hydrogen was released.
However, within 2-3 hours, the balloons started losing altitude and began falling down. I supposed it was caused by losing the gas slowly.
But when I tried to burn the ballon the next day it did not create the pop sound for the hydrogen test.
Please excuse me if this is a naive question. I'm curious since this is the first time I'm dealing with hydrogen and balloons. I attempted this for almost 4-5 time. And every time the balloon stopped flying within 2-3 hours. All other balloons filled with air did not lose gas.
I want to know what happens to the gas. Does it go out? Is it some sort of diffusion?
Thanks.
Hydrogen, having very small and fast moving molecules,  diffuses faster and through smaller holes than air. Your balloons seem to be permeable for hydrogen. Try a different brand, if it helps. But as others have mentioned, rubber is not the best material to keep hydrogen. Better is a metallised plastic.
Pure hydrogen just burns in a flame.  If you have ever  watched the film footage (1937)  of the catastrophic accident of the airship Hindenburg , it was just a huge scale of burning in a flame.
What makes an explosive &quot;bang&quot;is a hydrogen mixture with air, even better with oxygen. Because  hydrogen does not explode, until is contains &gt;6% v/v of oxygen.
Any binary chemical explosion of gases requires a self-sustaining chain reaction. That does not happen if a mixture contains too little of one of mutually reacting gases.