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Author Topic: Why did my bottle of fizzy water freeze when opened?  (Read 4889 times)

Stephen Blake

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Stephen Blake  asked the Naked Scientists:
   
Can you tell me why when last christmas time when we had the realy cold weather i had a bottle of fizzy water on the back of my van(on yer im a milkman by the way so the van is open) well the water in side was water untill i opened it then it froze right in front of my eyes. Has the fact that it was fizzy got anything to do with it?

Thanks for your time,

Stephen the  milky

What do you think?
« Last Edit: 15/10/2011 14:01:02 by _system »

Geezer

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Why did my bottle of fizzy water freeze when opened?
« Reply #1 on: 15/10/2011 15:08:50 »
I didn't know there were any milkmen left!

Anyway, yes Stephen. It does have to do with the fact that it's fizzy.

The fizz is produced by compressed gas (carbon dioxide) in the drink. The gas remains under pressure until you open the bottle. When you open the bottle, you release the pressure on the gas, so it expands, and that might also force some of the contents out of the bottle if you release the pressure too quickly.

When a compressed gas expands, it also cools down, potentially quite a lot, so it takes in heat from its surroundings. In this case, that's the liquid in the drink. If the liquid content was already close to freezing, the expansion of the carbon dioxide could chill it quite rapidly and remove enough heat to make it freeze.

chris

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Why did my bottle of fizzy water freeze when opened?
« Reply #2 on: 15/10/2011 20:50:54 »
We did this as a Kitchen Science experiment a few years back to answer a similar question sent in by someone in the States.

The answer is that when you open the bottle and permit the CO2 to escape, the liquid loses quite a bit of solute (the previously dissolved gas). Adding a solute to a liquid depresses the freezing point; conversely, removing the solute raises the freezing point.

So when you open the fizzy drink, the escaping CO2 causes the freezing point of the liquid to rise above the temperature of the liquid, so it freezes.

Another factor is that the disturbance to the liquid caused by opening it can also provide nucleation sites upon which ice crystals can begin to form, further increasing the likelihood of the liquid turning to ice.

Here's a link to our experiment and explanation.

http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/freezing-lemonade-bottles/

Chris

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Why did my bottle of fizzy water freeze when opened?
« Reply #3 on: 16/10/2011 06:28:31 »

The answer is that when you open the bottle and permit the CO2 to escape, the liquid loses quite a bit of solute (the previously dissolved gas). Adding a solute to a liquid depresses the freezing point; conversely, removing the solute raises the freezing point.


Nice explanation, but no ceegar ;D

The soda is still loaded with a large amount of CO2 even after the pressure is relieved (if it wasn't, it would not keep bubbling after you removed the cap. The pH of the soda (ginger to our Glaswegian readers) didn't suddenly change, so there was no instantaneous chemical reaction.

The soda in a bottle is a supersaturated mixture of CO2 and (mostly) water, meaning it is carbonic acid and an excessive amount of CO2 that has nothing to combine with.

As soon as the pressure is relieved, the excess CO2 expands (because there is no longer anything preventing it from expanding) and it immediately starts to absorb heat from its surroundings. If the soda was already close to its freezing point, the heat removed by the expanding CO2 causes it to freeze.

A one litre bottle of soda contains about three litres of CO2 (5.9g) compressed to fit in the bottle with the water and the other stuff. When the cap is removed from the bottle, the excess CO2 immediately returns to atmospheric pressure and expands. In the process, it absorbs 300J of thermal energy from its surroundings (the soda).
« Last Edit: 16/10/2011 07:30:38 by Geezer »

Bored chemist

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Why did my bottle of fizzy water freeze when opened?
« Reply #4 on: 16/10/2011 08:59:38 »
"The pH of the soda (ginger to our Glaswegian readers) didn't suddenly change"
Oh yes it does, and there's a fairly well known demo experiment using a pH indicator that proves it.

In any case, it's clear that a lot of CO2 leaves the solution so the freezing point will rise.

The latent heat of fusion of ice is about 80 cal /gram so, at best the CO2 loss could freeze about 4 grams of water into ice. I doubt anyone would notice that.


My guess is that the bottle of water was already below the freezing point, but supercooled. The sudden rush of bubbles nucleated the formation of ice crystals . The drop in temperature  and rise in freezing point due to loss of CO2 will have helped, but I don't think they could be responsible for the bulk liquid freezing unless it was already supercooled.
That also tallies with it happening  "last christmas time when we had the realy cold weather".

The story looks a lot like this video
http://www.youtube.com/watch?v=Ica4cLKdfWE&feature=related
except that in the video they don't open the bottle so it must be due to supercooling.
« Last Edit: 16/10/2011 09:10:08 by Bored chemist »

Geezer

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Why did my bottle of fizzy water freeze when opened?
« Reply #5 on: 16/10/2011 17:53:47 »
"The pH of the soda (ginger to our Glaswegian readers) didn't suddenly change"
Oh yes it does, and there's a fairly well known demo experiment using a pH indicator that proves it.

In any case, it's clear that a lot of CO2 leaves the solution so the freezing point will rise.

The latent heat of fusion of ice is about 80 cal /gram so, at best the CO2 loss could freeze about 4 grams of water into ice. I doubt anyone would notice that.


I knew I'd be on thin ice if BC showed up, but I thought I would try it on anyway  ;D (300J might be enough to make a couple of ice cubes!)

Geezer

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Why did my bottle of fizzy water freeze when opened?
« Reply #6 on: 16/10/2011 19:50:19 »
I think you must be right BC.

Even if the freezing point changed, the heat would still have to go somewhere - very quickly. Only a small amount could escape with the expanding CO2, and the heat couldn't suddenly transfer through the bottle into the surrounding air either. The only explanation is that the heat had already departed because the soda was supercooled.

BTW, unless I cocked up the calculation, the heat transfer required to take enough heat out of 1 litre of water to affect the phase change from liquid to solid in one second is a mere 334 kW, which could only happen if there was a whopping great temperature difference between the bottle and its surroundings. You'd think somebody might notice if that were the case  :)

Bored chemist

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Why did my bottle of fizzy water freeze when opened?
« Reply #7 on: 16/10/2011 21:10:58 »
That figure looks like the right sort of effective power.
It's perfectly reasonable if the energy was already stored in the liquid. Supercooled water isn't stable- it contains a fair bit of stored energy.

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Why did my bottle of fizzy water freeze when opened?
« Reply #8 on: 16/10/2011 22:45:53 »
That figure looks like the right sort of effective power.

I wish I could claim it required some serious number crunching on my part, but no. Latent heat of fusion for water is 334 kJ/kg. A litre of water is pdc to 1 kg, and because some clever chappie arranged for a kilojoule/second to equal one kilowatt.........

Bored chemist

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Why did my bottle of fizzy water freeze when opened?
« Reply #9 on: 17/10/2011 18:20:06 »
If you want to really frighten people, calculate the effective power (i.e. energy transfer rate) of filling a car's tank with fuel.

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Why did my bottle of fizzy water freeze when opened?
« Reply #10 on: 17/10/2011 18:55:54 »
Good point.

We touched on that a bit here:

"1 ml of gasoline has a thermal energy of 34 kJ, so thermal energy is produced in the engine at 1.75*34 = 59.5 kJ/s, or 59.5 kW (imagine how quickly that would heat your house!)"

http://www.thenakedscientists.com/forum/index.php?topic=41263.msg369581#msg369581

and that's when the engine is only putting out a small fraction of its potential power. Driving a car is a bit like running around with a gigantic blowlamp. Maybe they should be called "space heaters" instead of cars.


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Why did my bottle of fizzy water freeze when opened?
« Reply #11 on: 17/10/2011 20:12:33 »
Flying off at a tangent a bit, but I was quite surprised to learn that I could heat my house by burning gasoline for the same cost as electric heating. That was a couple of years ago, so it's probably no longer the case, but I don't think it will be all that different today. It sort of makes sense from an economics perspective because it's just the cost of energy and distribution.

This was in the US, but I would not be surprised if the situation in the UK is pretty similar.

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Why did my bottle of fizzy water freeze when opened?
« Reply #12 on: 17/10/2011 20:21:41 »
60KW is a fair estimate of the power released (mainly as heat) by a car engine.
However imagine the energy being transferred when you fill the tank.
I'm guessing the flow rate is something like 1 litre per second from the pump to the tank. (since I don't drive there's every chance I'm wrong about that- how long does it take to fill the tank, and how big is it?)
A litre is something like 34MJ.
So the effective power from the fuel pump is about 34MW. Even if the pump were 10 times slower, that's still a lot of power.
This is why it's not easy to recharge an electric car's battery in a hurry and also why there's a big problem with keeping electric cars warm in anything but warm climates

Geezer, do you know what the tax is like on petrol in the UK?
The price at the pump is something like £1.30 ($2.05) per litre or $7.75 per (US) gallon. How much do you typically pay?


Geezer

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Why did my bottle of fizzy water freeze when opened?
« Reply #13 on: 17/10/2011 20:49:09 »
BC, your calculation sounds about right. Yes, the energy transfer rate is really enormous which, as you point out,  is one of the reasons why it's so difficult to replace chemical fuels with alternatives.

At today's exchange rate, gasoline is about half that cost here. The tax is much less than in the UK.

It varies a bit in different parts of the US, but it's around $3.5 per US gallon where I live at the moment. A US gallon is pretty close to four litres, so that puts it around $0.9 per litre.

According to my electricity bill (which I just realized is unpaid!), I'm paying $0.064 per kWh, although there is a monthly service charge of $16.5 on top of that whether we use any or not. In the Summer we only manage get through about 500kWh in a month, but it's about four times that amount in January and February.

BTW,

Quote
60KW is a fair estimate of the power released (mainly as heat) by a car engine.

Yes, but that's when it's cruising along and the engine is only producing 10 to 15kW. A lot of cars have engines that produce well over 100kW. I'm embarrased to admit that my truck can actually crank out 250kW, at which time it will be burning over a megawatt in fuel. Fortunately, the only time it might ever approach that is when it's hauling a trailer up a mountain pass. It's hardly surprising that it makes quite a racket at the same time.
« Last Edit: 18/10/2011 04:17:21 by Geezer »

 

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