Salting ice in a cooler, or around a keg is known to get the beer colder faster. However there is a disagreement on why.
Two theories:
An anonymous person here known as "RB" says:
The earlier phase change of the melted ice increases surface contact of the slurry. This larger contact area of the water cools the beer.
Example: 28°F ice will turn into water of the same temperature. Otherwise the only water contacting the can would be at 32°.
Another theory is, which maintains the laws of thermodynamics, deals with the "heat of fusion". This the amount of energy that is required to make a phase change from a solid into a liquid. The phase change which usually takes place at 32°F, requires just about 80 calories for every gram of h2o. Remember it takes only 1 calorie to raise the same amount of water 1.8F after the phase change. The energy required to unlock ice's crystalline matrix is a large amount. Forceing the to happen earlier by adding salt requires massive amounts of energy from the environment (surrounding beer) actually pulls the slurry lower than the starting ice.
Example: 28°F Ice is salted. The resultant slurry is now at about 7F lower than the starting ice.
Beer Ice Salt Science Challenge.
Moderator: Chip
It's a gradient from the warmest areas inside the beer to the interface with the slurry where answer one prevails, then to the center of the slurry where answer two takes over. The gradient then goes back the other way toward the outside of the cooler to the warmth again.
It's like a keg party, where the drunkest people are the ones both closest and furthest from the keg with a reversing gradient in the middle area. I majored in beer dynamics in college.
It's like a keg party, where the drunkest people are the ones both closest and furthest from the keg with a reversing gradient in the middle area. I majored in beer dynamics in college.
Flyyyyy
Rob is correct as follows: http://www.newton.dep.anl.gov/askasci/g ... n01008.htm
To "explain" the lowering of the freezing point of ice "properly" requires knowledge of an area of physical chemistry called thermodynamics, which I am assuming you are not ready for, so I will try to put the concepts across as well as I can using as little of the jargon as possible.
Pure water and ice at 0 C. are said to be "in equilibrium" which means simply that they will co-exist indefinitely so long as the temperature remains at 0 C. This equilibrium is written as if it were a chemical reaction:
ice(pure) = water(pure) at 0 C.
If the temperature is raised above 0 C. the ice will eventually melt, and the ice and water are no longer "in equilibrium". If the temperature is lowered below 0 C. (Ignore the fact that water can sometimes be super-cooled below 0 C. and remain a liquid, at least for a while because that is an unstable condition.) If the temperature of the ice/water mixture is lowered below 0 C. the water will eventually all freeze leaving only ice, and the ice and water are no longer "in equilibrium."
There is a quantity called the "chemical potential" that is a property of the pure ice and the pure water. At 0 C. this "chemical potential" of the ice and the water are equal to each other. (Don't read too much into the term "chemical potential" literally because it is a jargon word. Think of it more as some measurable quantity that depends on temperature, pressure, and the composition of the things involved.The only thing you have to know about this "chemical potential" is that it increases with temperature, and it decreases as some substance is dissolved in the water. For solids and liquids like ice and water, this quantity, this "chemical potential", is independent of the pressure unless the pressure is very high. For our purposes you can say pressure has no effect. That leaves only the temperature and the composition of the things involved (ice and water).
In place of the pure water, suppose we have some salt dissolved in the water.
ice(pure solid) = salt water (liquid solution)
The presence of the salt lowers the "chemical potential" of the water. But the "chemical potential" of the ice remains the same. If we were to hold the temperature of the ice and salt solution at 0 C., the ice would all melt because it has a higher "chemical potential" than the salt solution. Remember I said that the addition of salt reduces the "chemical potential" of the liquid water. If the pure ice is to remain in equilibrium with the salt solution, it must lose some of its "chemical potential". Since pressure has no effect (you have to trust me on that), and no salt can dissolve in the solid ice, the only way for the ice to lose "chemical potential" is for the temperature to be lowered. Remember, I said that "chemical potential" increases with increasing temperature. And that is what happens. The temperature of the ice = salt solution decreases until the "chemical potential" of the ice and NOW the salt solution become equal.
For water, this requires that the temperature drop of (delta T)= -1.86 * m, where m is the number of moles of ions (both Na+ and Cl- for salt) per 1000 gm. water.
I know this sounds pretty complicated, but your question is really not as simple as you might think and your asking it shows your perception and curiosity about what is happening. That is why I tried to give you more than just the "standard answer" which really isn't true.
Vince Calder
Its hard to discredit RB when it comes to beer, I've tried.
I looked here:
http://en.wikipedia.org/wiki/Ice_cream_maker
Hand Cranked machines
These machines usually comprise an outer bowl and a smaller inner bowl with a hand-cranked mechanism which turns a paddle, sometimes called a dasher, to stir the mixture. The outer bowl is filled with a freezing mixture of salt and ice: the addition of salt to the ice causes freezing-point depression; as the salt melts the ice, its heat of fusion allows it to absorb heat from the ice cream mixture, freezing the ice cream.
The real engineering question is how to transport beer to astronauts and colonists on Mars. Can beer be made into "Tang" --- No.
I looked here:
http://en.wikipedia.org/wiki/Ice_cream_maker
Hand Cranked machines
These machines usually comprise an outer bowl and a smaller inner bowl with a hand-cranked mechanism which turns a paddle, sometimes called a dasher, to stir the mixture. The outer bowl is filled with a freezing mixture of salt and ice: the addition of salt to the ice causes freezing-point depression; as the salt melts the ice, its heat of fusion allows it to absorb heat from the ice cream mixture, freezing the ice cream.
The real engineering question is how to transport beer to astronauts and colonists on Mars. Can beer be made into "Tang" --- No.
I may be right more often than not about BEER, but after thinking about this particular question later (while sober), I have switched sides. I am allowed to do that after sobering up you know.
Energy is required to melt ice. That is a fact. If ice is melted with salt rather than heat, then the temperature around it HAS to drop because energy will be absorbed from the water around it when the ice changes phases to water. This should lower the average temperature of everything in the ice box (including the beer). Although the temperature will drop faster and go lower, the beer will later warm up sooner than it would have if salt were not added, since the TOTAL energy has never changed.
So what is the REAL VALUE of this information? Just this- if you want your beer to get colder quicker, add salt. If you want your beer to stay cold longer, drink from someone else's cooler until your beer has cooled to the appropriate temperature at the natural rate.
IF by some odd chance I was right the first time, that only proves that people really do get smarter after drinking, and then dumb down again after sobering up!
Energy is required to melt ice. That is a fact. If ice is melted with salt rather than heat, then the temperature around it HAS to drop because energy will be absorbed from the water around it when the ice changes phases to water. This should lower the average temperature of everything in the ice box (including the beer). Although the temperature will drop faster and go lower, the beer will later warm up sooner than it would have if salt were not added, since the TOTAL energy has never changed.
So what is the REAL VALUE of this information? Just this- if you want your beer to get colder quicker, add salt. If you want your beer to stay cold longer, drink from someone else's cooler until your beer has cooled to the appropriate temperature at the natural rate.
IF by some odd chance I was right the first time, that only proves that people really do get smarter after drinking, and then dumb down again after sobering up!
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tony de santis
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Ok so we know that beer cools quicker in a cooler then in a freezer due to increased surface contact are of the medium removing the heat. The second law of Thermodynamics states that Hot travels to cold or a High pressure travels to a low pressure. Therfore, because of the increased Delta T, the beer gives up its temperature more rapidly in the Salt/Ice solution rather than in Ice/ Water only solution.( The greater the Delta T, the faster the heat transfer).
OP thinks that OP is right. Heat of fusion 4 the win.
From Johnathan's link, just farther down the page.
These guys tried it, but couldn't measure the difference. They didn't do a good job. A small variance in the water added would change everything. "That's ignorant!" http://www.cockeyed.com/science/cold_be ... _salt.html
From Johnathan's link, just farther down the page.
When water molecules attach to or detach from the ice surface, something else happens. It turns out that a water molecule in ice has a lower potential energy than a water molecule in liquid water. This is because it is surrounded by other water molecules in a very precise arrangement. When a water molecule leaves the ice surface, it has to pick up some energy to break out of its potential energy "hole." Going the other way, when a water molecule attaches to the ice surface from the liquid, it must give up some energy to allow it to stay in its new potential energy "hole."
...
The ice will continue to melt, that is, the water moecules' detachment rate will be larger than the attachment rate, until the temperature is low enough that it's harder and harder for the water molecules in the ice to pick up the energy they need to detach. Finally, the attachment and detachment rates will be the same, so the energy flow will again be in balance. Then the temperature won't drop any further.
Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
These guys tried it, but couldn't measure the difference. They didn't do a good job. A small variance in the water added would change everything. "That's ignorant!" http://www.cockeyed.com/science/cold_be ... _salt.html
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Ken Andrews
- Site Admin
- Posts: 215
- Joined: Mon Jun 06, 2005 8:22 pm
- Location: Pasadena
Thermodynamics of beer
I never thought I'd be writing an essay about beer. Hang gliding leads people to do strange things.
Let's define a control experiment. We'll start with a cooler containing a slurry of ice and water, but no beer, that's been sitting around the LZ for a while. It's at equilibrium, so the ice is at 32 degrees, and so is the water. Now we drop in some cans of warm beer. The beer gets cold because heat flows from the beer, through the aluminum, and into the ice-water. How fast it gets cold is given by the heat equation: q=k*(T2-T1). That is, the rate of heat flow is equal to the temperature difference times the thermal conductivity of aluminum. Supposing the ice-water is well stirred, and the beer is well stirred, that's all there is to it.
Now let's modify that experiment by supposing that the cooler starts with a mixture of ice and salt-water. At equilibrium, this cooler is cooler, so to speak. Each teaspoon of salt per cup of water lowers the temperature about 2.7 degrees Farenheit, and the salt-water-ice mixture could be as cold as about -6 degrees Farenheit. The temperature difference between the beer and its surroundings is bigger, so according to the heat equation, the beer cools faster.
Now why is the salt-water-ice mixture colder? To answer that, we need two little facts. First, when one freezes salt-water, only the pure water turns to ice and the salt stays behind. Second, salt and water "prefer" to be mixed than separate; for example, it takes so much energy to extract drinking water from sea water that only cruise ships and Saudi Arabia bother to do so. Likewise, water "prefers" to be frozen if it's below 32 degrees. Hence, if one takes some salt-water and cools it below 32 degrees, the water has to decide what to do. It would like to freeze, but to do so, it would have to separate from the salt, which it doesn't like to do. Not surprisingly, it compromises: it stays as salt-water until it's somewhat colder than 32 degrees, and then it pushes out the salt and freezes. A little more precisely, the system picks a balance between minimizing energy, and maximizing entropy. Entropy is randomness, and there's more entropy in salt-water, where the salt molecules are randomly distributed through the water, than there is in pure water (or ice) and salt crystals. Mathematically, the system minimizes the Gibbs Free Energy, given by G=U-TS, where U is the energy, T is the temperature (in Kelvin), and S is the entropy. When T is small, minimizing energy is more important, and when T is large, maximizing entropy is more important.
But what if one adds salt to ice-water that is already at 32 degrees? Perhaps remarkably, the ice-water gets colder. It does this for the same reason: to balance energy against entropy. Some of the ice will melt (which takes energy and makes everything colder) in order to become water, so that it can dilute the salt, which increases the entropy.
Now which stays colder longer: a cooler with beer in ice and water, or the same cooler after one has added salt? If the cooler stays closed, we're back to the heat equation: q=k*(T2-T1). The speed at which heat flows into the cooler is equal to the thermal conductivity of styrofoam (small), times the temperature difference between the LZ and the contents of the cooler. This temperature difference is slightly bigger in the salt-water-ice situation, so the salt-water cooler warms up slightly faster. This doesn't matter though, because we're now talking about a cooler in the LZ full of cold beer, and it won't stay closed.
Let's define a control experiment. We'll start with a cooler containing a slurry of ice and water, but no beer, that's been sitting around the LZ for a while. It's at equilibrium, so the ice is at 32 degrees, and so is the water. Now we drop in some cans of warm beer. The beer gets cold because heat flows from the beer, through the aluminum, and into the ice-water. How fast it gets cold is given by the heat equation: q=k*(T2-T1). That is, the rate of heat flow is equal to the temperature difference times the thermal conductivity of aluminum. Supposing the ice-water is well stirred, and the beer is well stirred, that's all there is to it.
Now let's modify that experiment by supposing that the cooler starts with a mixture of ice and salt-water. At equilibrium, this cooler is cooler, so to speak. Each teaspoon of salt per cup of water lowers the temperature about 2.7 degrees Farenheit, and the salt-water-ice mixture could be as cold as about -6 degrees Farenheit. The temperature difference between the beer and its surroundings is bigger, so according to the heat equation, the beer cools faster.
Now why is the salt-water-ice mixture colder? To answer that, we need two little facts. First, when one freezes salt-water, only the pure water turns to ice and the salt stays behind. Second, salt and water "prefer" to be mixed than separate; for example, it takes so much energy to extract drinking water from sea water that only cruise ships and Saudi Arabia bother to do so. Likewise, water "prefers" to be frozen if it's below 32 degrees. Hence, if one takes some salt-water and cools it below 32 degrees, the water has to decide what to do. It would like to freeze, but to do so, it would have to separate from the salt, which it doesn't like to do. Not surprisingly, it compromises: it stays as salt-water until it's somewhat colder than 32 degrees, and then it pushes out the salt and freezes. A little more precisely, the system picks a balance between minimizing energy, and maximizing entropy. Entropy is randomness, and there's more entropy in salt-water, where the salt molecules are randomly distributed through the water, than there is in pure water (or ice) and salt crystals. Mathematically, the system minimizes the Gibbs Free Energy, given by G=U-TS, where U is the energy, T is the temperature (in Kelvin), and S is the entropy. When T is small, minimizing energy is more important, and when T is large, maximizing entropy is more important.
But what if one adds salt to ice-water that is already at 32 degrees? Perhaps remarkably, the ice-water gets colder. It does this for the same reason: to balance energy against entropy. Some of the ice will melt (which takes energy and makes everything colder) in order to become water, so that it can dilute the salt, which increases the entropy.
Now which stays colder longer: a cooler with beer in ice and water, or the same cooler after one has added salt? If the cooler stays closed, we're back to the heat equation: q=k*(T2-T1). The speed at which heat flows into the cooler is equal to the thermal conductivity of styrofoam (small), times the temperature difference between the LZ and the contents of the cooler. This temperature difference is slightly bigger in the salt-water-ice situation, so the salt-water cooler warms up slightly faster. This doesn't matter though, because we're now talking about a cooler in the LZ full of cold beer, and it won't stay closed.
And This Is Why It Is Nice To Have A PHD In The Club!
Now if we can only get Tom Casper (the other PHD in the club) to comment we MAY be able to determine the answer. 
Would you prefer that I pile it higher or deeper?
Well, my thermaldamnamics class was a long time ago..., for two substances to be in equilibrium at a given temperature their chemical potentials will be equal. The chemical potential is basically the change in the Gibbs free energy with the change in the amount of the substance in question. A plot of the chemical potential for ice, water and salt water (http://antoine.frostburg.edu/chem/senes ... u-vs-t.gif) shows that the salt water has a lower potential than the pure water.Thus, adding the salt will cause an imbalance in the rate at which water molecules melt from and freeze to the ice surfaces. As the ice melts it takes heat from the surrounding environment, lowering the overall temperature, until the ice and saltwater are at the same potential.
So, as Ken and (sober) Rob said, the contents of the salted cooler will get cooler than the contents of the unsalted cooler, and the beer will be cooler faster. But the cooler cooler will then get warmer faster, and the cooler beer will become warmer beer faster than the warmer beer becomes warmer beer.
Adding salt to the beer just makes bad beer.
Well, my thermaldamnamics class was a long time ago..., for two substances to be in equilibrium at a given temperature their chemical potentials will be equal. The chemical potential is basically the change in the Gibbs free energy with the change in the amount of the substance in question. A plot of the chemical potential for ice, water and salt water (http://antoine.frostburg.edu/chem/senes ... u-vs-t.gif) shows that the salt water has a lower potential than the pure water.Thus, adding the salt will cause an imbalance in the rate at which water molecules melt from and freeze to the ice surfaces. As the ice melts it takes heat from the surrounding environment, lowering the overall temperature, until the ice and saltwater are at the same potential.
So, as Ken and (sober) Rob said, the contents of the salted cooler will get cooler than the contents of the unsalted cooler, and the beer will be cooler faster. But the cooler cooler will then get warmer faster, and the cooler beer will become warmer beer faster than the warmer beer becomes warmer beer.
Adding salt to the beer just makes bad beer.
Tom
I still don't understand the concept.
Here is a clip of a desperate college student trying to cool warm beer with ice and salt(queued to start point):
http://youtu.be/ElyLZiZtrBE?t=2m52s
FYI The greatest naval battle of all history was won by the English at the Battle of Trafalgar in 1805 where they decimated both Spanish and French fleets.
All British Naval crew had daily allowance of 4 pints of beer and 1/4 pint of Rum or Brandy:
http://youtu.be/GWmby95E0Q8?t=9m9s
Here is a clip of a desperate college student trying to cool warm beer with ice and salt(queued to start point):
http://youtu.be/ElyLZiZtrBE?t=2m52s
FYI The greatest naval battle of all history was won by the English at the Battle of Trafalgar in 1805 where they decimated both Spanish and French fleets.
All British Naval crew had daily allowance of 4 pints of beer and 1/4 pint of Rum or Brandy:
http://youtu.be/GWmby95E0Q8?t=9m9s
doug, your link to "hack college" is a red herring. They kid is demonstrating that he hasn't taken chemistry class yet. Way too much water, not enough ice. In his case, the salt did basically nothing. The heat of the bucket of water did all the melting. He is basically exclaiming "wow, i cooled a beer to tap temperature"
For the trafalgar business. It is possible that they had cold beers to drink without ice or refrigeration. Down straight chilly beers like right out of the fridge. See the latitude of the battle area is about the same as ours, think dry air. During a high pressure system the dew point can drop below 40F. Evaporation would cooled the kegs to modern fridge temp. I like to think nelson figured this out, and this is the sole reason why they won. The invention of cold beer is the reason they have trafalgar square today. Too bad a man of that genius got shot through the spine.
For the trafalgar business. It is possible that they had cold beers to drink without ice or refrigeration. Down straight chilly beers like right out of the fridge. See the latitude of the battle area is about the same as ours, think dry air. During a high pressure system the dew point can drop below 40F. Evaporation would cooled the kegs to modern fridge temp. I like to think nelson figured this out, and this is the sole reason why they won. The invention of cold beer is the reason they have trafalgar square today. Too bad a man of that genius got shot through the spine.
Edit: cockeyed.com doesn't like people hot-linking their images.OP wrote:OP thinks that OP is right. Heat of fusion 4 the win.
From Johnathan's link, just farther down the page.When water molecules attach to or detach from the ice surface, something else happens. It turns out that a water molecule in ice has a lower potential energy than a water molecule in liquid water. This is because it is surrounded by other water molecules in a very precise arrangement. When a water molecule leaves the ice surface, it has to pick up some energy to break out of its potential energy "hole." Going the other way, when a water molecule attaches to the ice surface from the liquid, it must give up some energy to allow it to stay in its new potential energy "hole."
...
The ice will continue to melt, that is, the water moecules' detachment rate will be larger than the attachment rate, until the temperature is low enough that it's harder and harder for the water molecules in the ice to pick up the energy they need to detach. Finally, the attachment and detachment rates will be the same, so the energy flow will again be in balance. Then the temperature won't drop any further.
Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
These guys tried it, but couldn't measure the difference. They didn't do a good job. A small variance in the water added would change everything. "That's ignorant!" http://www.cockeyed.com/science/cold_be ... _salt.html
This is a fascinating subject, love learning about it, and I'm guessing it explains why they put salt on the roads in winter.
However, you've all been focusing on the temperature and have therefore lost sight of the true prize....the beer. And what is the ideal temperature for beer?
http://www.ratebeer.com/Story.asp?StoryID=479
However, you've all been focusing on the temperature and have therefore lost sight of the true prize....the beer. And what is the ideal temperature for beer?
http://www.ratebeer.com/Story.asp?StoryID=479
And here's the recommendation for what beers to drink ice cold:The first thing that should be addressed, however, are two very common myths. The first is that beer needs to be served very cold. The macrobrewers want you to believe this, and here’s why. The sensation of coldness inhibits the tongue’s taste receptors. Since macrobrews started positioning their products based on any feature they could imagine besides taste, the need to neutralize taste became important. An alcohol delivery system doesn’t need taste. In fact, taste usually gets in the way.
So I therefore refute this assumption:Very cold (0-4C/32-39F): Any beer you don’t actually want to taste. Pale Lager, Malt Liquor, Canadian-style Golden Ale and Cream Ale, Low Alcohol, Canadian, American or Scandinavian-style Cider.
And declare that us Brits have Trafalgar Square due to good beer that could be drunk warmer, not beers that had to be excessively cooled.For the trafalgar business. It is possible that they had cold beers to drink without ice or refrigeration. Down straight chilly beers like right out of the fridge. See the latitude of the battle area is about the same as ours, think dry air. During a high pressure system the dew point can drop below 40F. Evaporation would cooled the kegs to modern fridge temp. I like to think nelson figured this out, and this is the sole reason why they won. The invention of cold beer is the reason they have trafalgar square today. Too bad a man of that genius got shot through the spine.