Depends on where you are, how fast you’re going, and the velocity you impart to the gas molecules. If you’re in Earth orbit, the molecules would just spread out into similar orbits, unless you gave them enough speed to either escape Earth’s gravity entirely, or to counteract their orbital velocity and fall into some orbit that intersects the atmosphere.
Everything we shoot into space doesn’t fall back to Earth. If the object is traveling at or above its Escape Velocity it will never return to earth.
And if it’s orbiting the Earth it will stay orbiting the Earth forever, unless it bumps into something else.
wow. that’s my mindblowing quote for the day! thanks for that 
Incidentally, this is nowhere near the energy you’d need to blow up the Earth. You’d need a chunk of antimatter about the size of a city to do that.
Mr. Neville gave a midterm in his astronomy class last week, and this was one of the problems on it. He said I inspired him to come up with it. Awwww.
Way back in Babylon 5, when Delenn said, “We are star stuff,” she wasn’t kiddin’ Virtually everything heavier than hydrogen was forged in the heart of a long dead star.
If you’re an optimist, you can say we’re made of star stuff.
If you’re a pessimist, you can say we’re made of nuclear waste.
…Or during the supernova marking the moment of death.
Depends on how close Earth is when you shoot the air out. If Earth is the closest gravity well, then yes.
And last I checked everything we shoot into space doesn’t make it back, Neither Voyager Probe is due to fall back to Earth in the coming weeks, or ever. Viking, ditto, Beagle, Casini… We shoot a lot of stuff out there that will never come back.
Both Voyager probes are long gone, never to return*. Voyager-1 left the solar system about five years ago. Voyager-2 left the solar system about two years ago. They will continue on into interstellar space forever.
[sub]*- Well, if it comes back it will probably be as the planet collecting V’ger. 
[/sub]
On a religious board I participate in, after this point was made in a Creation vs. Evolution debate (which of course regarded Big Bang cosmology and nucleosynthesis as part of ‘Darwinian theory’ :rolleyes: ), someone commented “We are made up of stardust.”
I knew my cue. I quoted that, and responded, “We are golden … and we’ve got to get ourselves back to the Garden.”
Somewhat tangental to the overall topic of the thread, but let me note that oxygen isn’t necessary to combustion. An “oxidizer” needn’t actually be oxygen.
Oxygen just happens to be a prevalent and geared towards producing oxydizers (or something).
Want another one?
Since the atoms that make up our biosphere are more or less indestructible, and are very well recycled, and you’re made up of SO MANY of them, you right now almost certainly have atoms that used to belong to Julius Caesar.
Well, I already had my mindblowing quote for today so this is getting a bit too much, but thanks all the same. 
ETA: can we say with the same certainty that I now have atoms that used to belong to Adolf Hitler? :eek:
Yes. With every breath you take, on average you inhale four molecules that Hitler exhaled in his last breath.
Yeah, unless you specify, there’s much more space beyond the gravity well of Earth than within it. Much, much more.
Oh, so much, much more.
I think Carl Sagan said that a bit before B5. I don’t know if he invented it. Cosmos would be a cool thing for a kid to watch.
BTW, if the OP is going to talk about supernovas, it might be wise to mention that the Sun isn’t nearly big enough to explode in this way. And it is probably better not to mention what will happen to it. It might happen billions of years in the future, but little kids don’t have great concepts of time. BTW Phil Plait, our very own Bad Astronomer, has an excellent book called Death From the Skies.
No. The primary fusion reaction in a star is driven by the gravitational pressure from its huge mass. It’s not a chain reaction like in a fission reactor or bomb. The energy produced by each fusion reaction actually serves to push apart the atoms, making the core less dense, slowing down the reaction. Until they run out of fuel, stars are in a dynamic balance between gravitational pressure compressing in, and fusion energy holding the mass apart.
Thank you. *Babylon Five *and *Cosmos *indeed. Joni sang about being billion year old carbon in 1969.