Why Does Gas Float Upward: Investigating Mass Difference

AI Thread Summary
Gas rises instead of falling due to buoyancy, which is influenced by mass differences between gases and the surrounding air. Lighter gases, like helium, are less dense than air, causing them to float, while heavier gases, such as carbon dioxide, sink. The discussion highlights that buoyancy is the key factor, as demonstrated by the behavior of objects like boats and stones in water. On the moon, where there is no atmosphere, a helium balloon would fall because there is no medium to provide buoyancy. Understanding these principles helps clarify why different gases behave as they do in various environments.
AstrophysicsX
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Why does gas float upwards instead of falling towards the Earth ? Is it a mass difference ?
 
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AstrophysicsX said:
Why does gas float upwards instead of falling towards the Earth ? Is it a mass difference ?
What kind of gas are you talking about?

If you have a balloon filled with the a gas that is lighter than air (eg. He - an atom of He is lighter than a molecule of N2/O2) the balloon will rise. But if it is filled with a gas that is heavier than air (eg. CO2), it sinks.

AM
 
Why does it being lighter than air have anything to do with it floating upwards. Isn't mass supposed to be attracted to the Earth, therefore falling?
 
When you drop a stone into a lake, it sinks. When you put a boat into a lake, it doesn't sink. Don't the stone and the boat both have mass? Why does one sink and the other float?
 
Another way to look at this might be:
Would a helium balloon rise or fall on the moon? Answer: It would fall.
 
But why ? Explain please.
 
AstrophysicsX said:
But why ? Explain please.

Things float because of differences in buoyancy. There is no air or any other gas on the moon (I think) so there's nothing for a helium filled balloon to float on or sink in. The force of gravity would slowly pull it down.
 
Last edited:
AstrophysicsX said:
But why ? Explain please.
People are trying to help you by making you think, rather than spoon feeding. Do you not know why boats don't sink? Can't you apply that to a balloon? Even if you aren't sure, answer questions with a guess. Exercising your brain makes it work better.
 
lolarogers said:
Yea. comparatively gas has low wait. that's why its floats.

Yeah, gas doesn't stick around too long...
 

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