Do gases dissolve faster in cold water?

[vinz]

We know that colder water can hold more gases before becoming saturated. But do gases dissolve faster in colder water?

In practical terms, does it make much difference to put the CO2 reactor AFTER the chiller?

[PeterGwee]

I doubt so as it is the mixing/flow rate that determines how fast the gas dissolves. It might help if your reactor isn't that efficient.

Regards
Peter Gwee

[armani]

i also think its according to the mixing n flow... if the CO2 bubble remians in the water for a longer period then more of it will dissolve in the water...

[vinz]

I mean besides the flow rate, etc. Let's consider this thread assuming that all else is equal.

[Rupert]

Good question, I would have thought that warm water would dissolve gases quicker as warmer water loses gases quicker, whereas cold water holds the same volume of gases for longer.

[armani]

ok, i give explanation from my knowledge of chemistry...

according to chemistry, gases at high temperatures vibrate more than in lower temp... therefore, at high temp, the gas will possess more energy to dissolve in the water faster... at low temp, the vibration will not be so strong, so comparing hot n cold, the amount of gas dissolved in hot water will be faster than in cold water...

this is what i feel n what i can think of... any other ppl who feel differently do let us know... thanks very much...

regards

aramni

[|squee|]

I did a search in google, and came upon this webpage.

Quoted:
However, gases, with negative heats of solution, (delta)H< 0, are more soluble in cold water.

Not sure how true is this, but given the webpage is supposed to be based on educational material, it should be correct?

But then again, does solubilty mean ability to dissolve?

[Goondoo]

I think your one too chim lar.... Vinz show me this while we was discussing just now....
Link

Cheers,
Goondoo

I did a search in google, and came upon this webpage.

Quoted:
However, gases, with negative heats of solution, (delta)H< 0, are more soluble in cold water.

Not sure how true is this, but given the webpage is supposed to be based on educational material, it should be correct?

But then again, those solubilty mean ability to dissolve?

[|squee|]

ok Billy, thanks.

But does solubility relate to ability to dissolve? -- I think this question was redundant, of course it's a yes.

So that really means chilled water = C02 dissolves at a more efficient rate?

[PeterGwee]

The higher the temp, the less gas(any gas for that matter) will be
held in solution.

More gas can be held in the solution doesn't mean the rate of dissolution is faster imo. Take 2 taps of flowing water of equal rate to fill up 2 plastic bottles of different size. The bigger bottle (water with lower temperature) has the ability to hold more water than the smaller one (water with high temperature)...thats what I think is going on. I might be wrong though...

Regards
Peter Gwee

[PohSan]

In practical terms, does it make much difference to put the CO2 reactor AFTER the chiller?

Basically, I don't think that there is a great temperature difference between before and after chiller after the tank temperature has stablised.

Regards,
Ong Poh San

[mrs budak]

I asked our chemist and this is what he said:

Lower water temperature, gas will become saturated faster.

Higher temperature, gas will become saturated slower.

Solubility of gas depends not just on water temperature but also other water conditions like pH.

Don't think this answers the question of solubility of gas but hope it helps anyway.

[vinz]

Thanks MrsBudak... now you have to change your signature...

So:
1. cold water can hold more gas, but becomes saturated faster.
2. hot water can hold less gas, but becomes saturated slower.

Based on those 2 points, I think we can conclude that gas do dissolve faster in colder water.

I think Armani explained why... assuming he remembered his chemistry correctly.

Poh San has a point... if water temperature is within the set range (i.e chiller is not chilling), the difference in water temperature before or after the chiller is negligible. A decent set up shouldn't have the chiller running for more then 10 to 20% of the time. In that case, it won't matter so much whether the reactor is before or after the chiller.

[Plantbrain]

Think energy!

At higher temperatures, gases are more active and have more energy
with which to escape from solution.

But does it matter much?
In some cases yes.
In this case? Not at all.

Regards,
Tom Barr

3rd annual Plant Fest July 8-14th 2005!
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Regards,
Tom Barr

[juggler]

When you boil water, the dissolved gases in it escapes as bubbles.
So cold water can retain more dissolved gases.

[kayser78]

haha. guess it all boiled down to kinetic theory of particles and point of saturation.

so for warm water, more energy is supplied to the gas and hence more solubility. However, saturation point is lower and therefore less dissolved gas can be retained.

so cold water, it will be the reverse.

[Plantbrain]

The bubbles you see BEFORE the water boils on the bottom/sides, that's the gases, N2, O2, CO2 etc.

Once the water boils and continues, that's not dissolved gas anymore.
Think about it, how much gas could be locked up and how long can you boil water with all the bubbles for before the gases might be gone?

A very very long time.

As you heat up the water, you are breaking down the liquid molecules so that it can turn into a gas. Bubbles are created in the water closest to the bottom of the pot first. But the pressure of the outside air will squash those bubbles at first because they don't have enough pressure inside them to stand up to the outside air pressure. As more energy goes into making those bubbles though, they will begin to be able to stand up to the outside air pressure. When they get to the point where they can stand up to the outside air pressure, you'll see massive bubbles coming off of your water, the temperature of your water will top off and your boiling point will be reached.

This is gas, H2O vapor, not dissolved gases like N2, CO2, O2 at this point.
All the energy goes into transforming the liquid to gas at this point and the temperature will not increase further.

While colder water holds more gases than warmer water, the solids are not all the same when it comes to dissolving them into warmer water(the solvent has more energy). A few dissolve better in colder water(I think Ce(SO4)2 and NH3), but most don't.

These phase changes from solid to liquid and liquid to gas can trick you, some think that warmer water will hold more gas since there is more "space" eg, the H2O is less dense therefore more room to hold the gas.

Water is tricky stuff.
I'm not a chemist but water is key to what I do.

Regards,
Tom Barr