explain. why?

Question

Gas molecules at room temparature have velocities comparable with those of rifle bullets, yet a gas like ammonia with strong odour takes several second to diffuse accross a room. why?

Answer 1

I imagine it is because the molecules are constantly bumping into other molecules so it takes longer to get there.

Answer 2

It's primarily a mass issue. A rifle bullet can cover the distance from one wall to another, not because it doesn't encounter anything, but what it encounters isn't enough to stop it. Any gas molecules in the air get brushed aside with only the slightest slowing (which we call friction) - because the mass differences are so severe.

For gasses, the room is, effectively, packed with obstacles. Each molecule can only go a short distance before it runs into something that interferes, causing it to ricochet. If you were to release the gas in a vaccuum, it'd cross a lot faster. Of course, you'd have a hard time breathing, so smelling it would be a problem. ;)

Answer 3

Well, they're probably pretty erratic, and don't just go in straight lines. Plus they're exceedingly small, so they probably stay in an area that's like a millimeter wide.