A dramatic demonstration -- with exclusive video! -- of why the same gas that heats your house can also make it explode
Posted 02.19.2009 at 3:50 pm
17 Comments
Whooomph!
Mike Walker
Living in the Midwest, where heating homes with propane is common, I periodically see reports in the local paper that yet another unoccupied house has exploded. They often note that the roof was found in the basement, while the walls were spread some distance into the neighboring fields.
Roof-in-basement syndrome begins when propane, which is heavier than air, leaks and fills up the lower levels of a house, mixing with the home's ambient air. Once the layer of gas reaches the height of a pilot light in a stove, it triggers a huge explosion. (The refinery adds a very strong odor to propane, so if people are home, they typically notice the leak before the concentration approaches a dangerous level.)
Why does the same gas that burns gently in a furnace turn into an explosive menace when it leaks? Without oxygen, propane can't burn. You could light a match inside a propane tank, and nothing would happen. Furnaces control the rate of burning by mixing propane with air slowly as it burns. But premix large amounts, and the results are very different.
The Setup: Mike Walker
I've done this demonstration several times with people unfamiliar with just how much power can be tied up in a few soap bubbles. I've never actually blown a window out, but I think I have knocked a few socks off.
Making Hydrogen Bubbles
THE SETUP
High-pressure tanks of hydrogen [red] and oxygen [yellow] supply the raw elements for this demonstration. What keeps it safe are devices at the ends of the hoses called flashback arrestors that prevent the gases from mixing inside the canister.
Achtung! Theodore Gray is trained in lab safety. Don’t try this at home. See more of Gray’s work at periodictable.com.
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Why does a Hydrogen and Oxygen mixture explode? wouldn't it turn into water?
It does turn into water. Just after releasing a lot of energy. A water molecule has less energy than the components that make it up. This is where the extra energy of the explosion comes from. Coincidentally, this is also what allows hydrogen fuel cells to work. The reverse of this process is possible by the application of energy, most notably in the electrolysis of water to generate pure hydrogen and oxygen.
Nice demo,but a little misinformation re the propane.
1.You could drop a match into a propane tank -- well, you can't because it's pressurized and mostly liquid (That's what the L in LP stands for).
2.The propane explodes because there's so much of it available. In the furnace, only a small amount is exposed. So, the story doesn't really relate to the demo.
3.'Natural' gas, which is lighter than air, also causes home explosions when a leak occurs -- and they are amazingly violent.
@ ford2go
1. IF you could drop a match in a propane tank it would not explode, the IF should have been mentioned in the article though.
2. In a leaking furnace the gas slowly seeps out and mixes with the air until it is set off.
3. Propane does the same thing when a leak occurs.
The article relates just fine.
Gaffe Alert: "You could light a match inside a propane tank, and nothing would happen."
But would a match light in the first place with no oxygen present?
First, the article says to light a match inside, not drop in a lighted match. Thus the match is already inside the pressurized tank when it is struck.
Two, part of a old-fashioned "Blue Tip" matches have oxidant already mixed in, like gunpowder, but slower. That was the lighter blue art at the very tip. Thus you can light one in a vacuum - of course, when the oxidant runs out, the fire stops. But it's enough to ignite propane, if it will ignite. (As a kid I used to whack them with a hammer and get a nice bang, just like little gunpowder "caps" for cap guns.)
Hydrogen and methane will also collect, mix, and explode, but they gather at the ceiling and work down to the pilot light. However, many houses are permeable enough that the mixture leaks out faster than a small leak can replace, while propane just pools (unless your house is on a hill and the cellar door leaks) - thus the methane never reaches the pilot light. In a nice tight house, or with a big leak, yes: big boom.
Wow dude, now that looks like a lot of fun!
RT
www.anonymity.eu.tc
my physics teacher in high school used to have 2 special days every year when he would come in dressed as dr fire or dr ice and we would spend the whole day blowing things up or freezing them. he would fill balloons with different mixtures of gasses and set them off. one explosion was so big it blew all the ceiling tiles in the front of the room out. loved it.
yeah in my 8th grade class we did hydrogen bubbles, it was great, still have burn marks in the ceiling tiles. we did also play with dry ice and liquid nitrogen i love that stuff.
this is very similar to an experiment i conducted recently wherein i farted in the bathtub while smoking a cigarette.
We used to make hydrogen balloons with a glass Coke bottle, aluminum foil, Drano and water. It would fill a punching balloon 2' in diameter. Instant Hindenburg! The reaction is exothermic which is why you need the heavy glass bottle and the heavy rubber punching balloon.
Most kids in science class remember this type of thing best because it is exciting and fun. If the teachers in all of the kids classes helped the kids to make school work this much fun how much more could all the kids learn.
You don't think that Math can be that much fun? Make the math problem something that has the kids competing against one another.
Same thing with English try seeing how much funny it would be to learn how to write a really good short story.
When teachers finally learn. HOW TO TECH. Then we will have a lot more really intelligent students graduating from all their classes.
dray
I think that using gasoline would be way cooler. Let's see a video of that!
Wow that's cool, nice video. Gotta agree with seeing a video of gasoline though ;)
My resource on vitamins www.wisemensvitamins.com
It would create water as a byproduct of the reaction.
Pure Hydrogen plus fire equals whoomph
Large quantity of H mixed with air/oxygen equals boom
Wouldn't H plus 02 be an endergonic reaction or does that only apply to biological molecules?
For gasoline to explode, it has to be vaporized. Spraying it into a balloon filled with air would work.