Where do the bubbles in boiling water come from?
Discussion
erolb said:
As water starts to simmer you see a string of small bubbles rise from the bottom of the pan. Bubbles I take it must contain some gas, if the water has no air in it, where does this gas come from?
Thanks in advance
water does have air in it (well dissolved oxygen and other gases at least)Thanks in advance
erolb said:
As water starts to simmer you see a string of small bubbles rise from the bottom of the pan. Bubbles I take it must contain some gas, if the water has no air in it, where does this gas come from?
Thanks in advance
Water is H2OThanks in advance
2 parts Hydrogen to 1 part Oxygen - both gases
When water is heated, these gases are less soluble in the water. When you boil water, the bubbling is dissolved gases being released.
Even simpler, but more detailed...
When the water reaches 100 degrees Celsius, it turns into a gas called water vapour.
This gas is less dense than the water around it, so it rises to the top. Most of the bubbles start at the bottom, because that's where the heat is. The more heat you apply, the more bubbles you will get. The water is turning into a gas very quickly, and lots of bubbles form, and all try to rise to the surface at once. They push the water out of the way as they rise, and jump out of the surface. This is what we call 'boiling water'.
erolb said:
if the water has no air in it
There's yer problem. The water will have air dissolved in it, and as the water gets hotter the air will come out of solution as... bubbles.Of course, as the water gets close to boiling point, small steam bubbles will start to form as well, initially using imperfections in the surface of the pan as seed points. Eventually, when all the water is at or above boiling point, bubbles of steam will form freely in the liquid.
GTSDave said:
Water is H2O (2 parts Hydrogen and 1 part Oxygen) both are gasses in their natural form, but will bond to form WATER under 'normal' conditions, when heated the molecules separate and form as gasses, but will cool again and form water (Steam) in a cooler environment.
Hopefully that explains it in a simple format
So, will boiled water, say in a pot with the lid off and boiled for 3 minutes, still be the same H2O as before boiling. Meaning does the oxygen and hydrogen separate and evaporate at the same rate as each other? or could it be H1.8 O for example? Hopefully that explains it in a simple format
IYSWIM
fleetelise said:
it contains dissolved gas
KaraK said:
water does have air in it (well dissolved oxygen and other gases at least)
These two have the right idea.JRM said:
H2O
hydrogen and Oxygen, both can be gases when I last checked
hydrogen and Oxygen, both can be gases when I last checked
GTSDave said:
Water is H2O (2 parts Hydrogen and 1 part Oxygen) both are gasses in their natural form, but will bond to form WATER under 'normal' conditions, when heated the molecules separate and form as gasses, but will cool again and form water (Steam) in a cooler environment.
Hopefully that explains it in a simple format
These two, however, have no idea at all. They can be dismissed as fools and mocked.Hopefully that explains it in a simple format
John MacK said:
GTSDave said:
Water is H2O (2 parts Hydrogen and 1 part Oxygen) both are gasses in their natural form, but will bond to form WATER under 'normal' conditions, when heated the molecules separate and form as gasses, but will cool again and form water (Steam) in a cooler environment.
Hopefully that explains it in a simple format
So, will boiled water, say in a pot with the lid off and boiled for 3 minutes, still be the same H2O as before boiling. Meaning does the oxygen and hydrogen separate and evaporate at the same rate as each other? or could it be H1.8 O for example? Hopefully that explains it in a simple format
IYSWIM
Seems some odd replies so far...
Water has dissolved gasses in it, CO2 being one (as talked about a lot with seas being carbon sinks as the CO2 dissolves in it). Heating it reduces the ability for gasses to dissolve in the water, so they are released as bubbles.
Once you get to boiling point, the water boils in small areas, becomes H2O gas (NOT seperate H and O gasses) and bubbles up. The Surface tension exhibited by the stong H bonds in water keep it in nice round bubbles.
Water has dissolved gasses in it, CO2 being one (as talked about a lot with seas being carbon sinks as the CO2 dissolves in it). Heating it reduces the ability for gasses to dissolve in the water, so they are released as bubbles.
Once you get to boiling point, the water boils in small areas, becomes H2O gas (NOT seperate H and O gasses) and bubbles up. The Surface tension exhibited by the stong H bonds in water keep it in nice round bubbles.
Is it anything to do with pressure/ termperature changes?
With most oil when it is under high pressure and temperature underground it has a lot of disolved gas in it. Thus when it gets taken out the pressure and temperature drop, and the gas comes out of solution. That's why you get less oil out than there is underground. It's also the reason they used to flair the gas, as they didn't have any use for it and it was dangerous to store.
With most oil when it is under high pressure and temperature underground it has a lot of disolved gas in it. Thus when it gets taken out the pressure and temperature drop, and the gas comes out of solution. That's why you get less oil out than there is underground. It's also the reason they used to flair the gas, as they didn't have any use for it and it was dangerous to store.
El Guapo said:
fleetelise said:
it contains dissolved gas
KaraK said:
water does have air in it (well dissolved oxygen and other gases at least)
These two have the right idea.JRM said:
H2O
hydrogen and Oxygen, both can be gases when I last checked
hydrogen and Oxygen, both can be gases when I last checked
GTSDave said:
Water is H2O (2 parts Hydrogen and 1 part Oxygen) both are gasses in their natural form, but will bond to form WATER under 'normal' conditions, when heated the molecules separate and form as gasses, but will cool again and form water (Steam) in a cooler environment.
Hopefully that explains it in a simple format
These two, however, have no idea at all. They can be dismissed as fools and mocked.Hopefully that explains it in a simple format
You think that the gas coming out of the pan is additional dissolved gas do you, nothing to do with Hydrogen and Oxygen do you? How is it possible to boil a pan dry then if it's unrelated?
John MacK said:
GTSDave said:
Water is H2O (2 parts Hydrogen and 1 part Oxygen) both are gasses in their natural form, but will bond to form WATER under 'normal' conditions, when heated the molecules separate and form as gasses, but will cool again and form water (Steam) in a cooler environment.
Hopefully that explains it in a simple format
So, will boiled water, say in a pot with the lid off and boiled for 3 minutes, still be the same H2O as before boiling. Meaning does the oxygen and hydrogen separate and evaporate at the same rate as each other? or could it be H1.8 O for example? Hopefully that explains it in a simple format
IYSWIM
Edit: JRM, you are confused; the reason a pan boils dry is that the liquid water has all been turned into steam. The bonds between the hydrogen and oxygen atoms in a molecule of water are FAR too strong to be broken by boiling the water.
Also, consider this: if water DID break down into gaseous hydrogen and oxygen, why will boiled water condense back into liquid water droplets on, say, a cold bathroom mirror? Both oxygen and hydrogen only become liquid at very, VERY low temperatures.
Edited by Quaint on Thursday 17th December 15:05
Quaint said:
When water (H2O in the liquid phase) boils, it becomes steam. A.k.a. "water vapour", a.k.a. H2O in the gaseous phase. The water molecules don't "break up" into their constituent hydrogen and oxygen atoms. El Guapo is very much correct...
+1Heavens. You cannot seperate Hydrogen and Oxygen from each other simply by heating them. The usual method is electrolysis I believe, if I recall my childhood chemistry correctly.
The bubbles are, indeed, water tranforming from it's liquid state to it's gaseous state below the surface. It's less dense in gaseous form and hence rises to the surface where it is given off as water vapour.
A few short inches from the surface it cools again and the water vapour condenses into tiny droplets of water we call steam.
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