Boiling water in Zero Gravity?

Question

Hey everyone.

I was wondering if you could all help me with this question I've been pondering.

Let's say you're in space where there's zero gravity.

The cabin of the ship is pressurised to that of sea level, 101.3 kpa I believe.

So you pop a balloon of water and let the blob of water float. Then you increase the temperature of the room to 100c, the boiling point of water at sea level.

Here's where I can't come to a definite answer:

When the bubbles that form in the blob of water start to rise, would they rise to what we would call the top of the blob of the water, we'll say towards the top of the space craft? What would be consider going up.

Or would the bubbles rise to the surface of the blob of water in all directions as technically, there is no up and down, left and right in zero gravity?

If I can get your input on this, that'd be awesome.
10 points for the best answer.

Answer 1

Given the restrictions you've placed on it, I'd have to say ...

Since you are heating the room and Not applying the heat directly to the water (say for example via microwaves).... The water blob would be heated from the exterior... no bubbles would form in the interior, they wouldn't have time. The exterior would evaporate into the surrounding air. Eventually you would have all the water heated to 100c and it would be in the air, high humidity :)

The real trick would be getting the blob of water to stay still long enough to be heated ... as convection currents developed within the room (unless that's a thought experiment too, using a room heater that is 100% uniform across all walls :)), the blob of water would have a high probability of impacting with a wall before it heated to 100c.

Edit:
Addendum: Thanks to "noonehomebutlightsareon" for posting the link to the micro gravity boiling experiment. Very cool.. however, that's not the same as the question posed here... in that experiment the heating element is inside the blob of water... "eversky_2000_2001" posed the question with the room being heated, therefore the air is what will heat the water, not a heating element within the water. Two different experiments with, possibly, two very different results.

Answer 2

Wow, that's awesome. Just hope you're not in the room, too. :D

I think the bubbles would just want to escape the blob of water, and since there is no up in zero gravity, they would squeeze out of every side. But- the reason bubbles come to the top of a pot of boiling water is because they are lighter than the water, thus trying to "float" on the water... But, in space, can things "float" on each other? My only question is whether having air in the zero gravity compartment with the blob of water, as opposed to an airless vacuum, well, you wouldn't be able to raise the temperature high enough to boil water if there was no air... So, ultimately, I think the bubbles will just squeeze out the sides, and come out the direction that is the closest to the edge... Wonder if it's been done before...

Ah! What if they don't leave the blob of water? Can they do that?

Answer 3

That's a great question. Lets think it through.

Bubbles rise on earth because the air in the bubbles is lighter than the water they're in, so they rise as a result of gravity.
If there were no gravity (but the air pressure is sea level as you stated), then I think the bubbles would move out in the blob of water in all directions equally.
Not due to gravitational forces (there are none) but due to the kinetic motion of the air molecules themselves in the bubbles causing them to continue to move.

Or they may all just stay where they are in the blob of water, and gradually would grow until the water was displaced by the bubbles.

I don't know if they ever did that kind of experiment in any space mission, but it would be interesting.

Answer 4

First, great question. I am going to speculate here because i don't really know the answer.

When water becomes steam, it expands rapidly at the moment of vaporization. I think that will cause the water bubble to burst into smaller bubbles.

Just speculation, but that is what I think. . .

Answer 5

It's been done.

Here's a video of what happens, with a discussion.

Answer 6

yes it can be done