No, this isn't for school, I'm just deathly curious. I'm in MN, it's well below freezing outside, and I forgot two pounders in my car. I grabbed them a little while ago and figured I'd open one and see how it was doing. It was still kind of icey, but in small slivers and not in a big chunk, so I could sip a little at a time. So I took a sip, and then set it down, and a minute later the beer was slowly rising up out of the can. What's the physics principle behind this? I assumed that, since (most) liquids expand when they freeze, it wouldn't rise. Anyone know why?
I live in Northwest Queensland Australia so a couple of questions What is a "Two pounder"? Why does it have beer in it? And can beer really Freeze outside? We have had blistering heat all summer AND winter this year!!
Not quite. Since the liquid was still liquid, the CO2 EXPANDED upon release from the can, and the expansion the gas produced a temperature drop of the solution, plus the decreased volume of gas in solution lowered the fusion point of the water/alcohol mixture. The formation of ice expands the specific volume, and pushes liquid out of the can. Since the mixture was liquid until opened, and then froze up, "thaw" is exactly what wasn't happening.
It's going to be a really cold winter here in Los Angeles. It's already down to fifty-two fahrenheit, and the wife is worried that our SIBERIAN HUSKIES might be cold....
A pounder is just 16 ounce beer can, usually of a specialty type. If you had a 16 ounce generic or otherwise common beer, you usually wouldn't call it a pounder. The two I got were from Big Wood Brewery. The unopened one is "Jackpine Savage", and American Pale Ale, and the opened one is "Morning Wood", a coffee stout. Oh, and I'm in Minnesota so things freeze pretty quickly. Yesterday morning after I parked my car, my beard - still moist from the shower - formed icicles on my way to class. It was only about a hundred yard walk. hmmm. interesting. I'll be honest, still trying to get that. At first it was like a lightbulb went off because I remembered a law, and then I realized, "nope, that doesn't explain this one."
That isn't quite how I understand that it happens. The process is called "supercooling" and the liquid in question actually has a temperature below its freezing point. If there are "nucleation sites" a liquid will freeze at its freezing temperature. However, if there are no nucleation sites the liquid may not turn into a solid until it is well below its freezing temperature. For example, given the right conditions and purity, it is possible for distilled water to be brought down to a temperate of -55F without turning into ice. So in the case of the OP, the beer actually was slightly below its freezing temperature before it was opened. Once it was open the CO2 turned into bubbles, immediately creating nucleation sites, thus allowing the liquid to freeze. Anyway, that is hoy the Mythbusters explained it.
haha thanks, that makes slightly more sense! boy, that looks like fun. kind of makes me want to start another one of those "what are you drinking" threads. I just lose interest once it becomes a long list without personality or conversation.
The beer was reacting to the temperature change. It was changing states from a solid back to a liquid and the energy or the temp in the room was enough to add energy at a high enough rate so the yeast( I assume) or whatever causes the foam was activated.
I'll try and do this from memory without internet searches. But I think the formula PV=nRT applies here. Ideal gas law? P=pressure, V=volume, n=number of moles (the amount of something, kinda like total atoms in the can), R=a constant whose value I forget, T=temperature. So when you opened that can, the P on one side of the equation was greatly reduced. Something must make up for this. And the temperature, total amount of the substance, and the constant R, aren't going to change much, if it all. That leaves V. The volume must increase to make up for the decrease in P. That about right lol?
I'm no expert, but everyone is talking about temperature changes. That's not what was changing when he opened the can. The major changes were in pressure and volume. The temperature of the beer, as I'm sure Troi would attest, was not drastically changing.
What made the volume change that caused the energy to react when he opened the can? GOD. Please explain.
That's why I said I'm no expert. But I think we need to start with PV=nRT for us laymen. The beer has nothing to do with it, I don't think. It is the CO2 in the beer that is expanding into more volume, because it is a gas, and the equation applies only to gases. That's as far as my knowledge will allow me to go. I know that if he changed the pressure that much, something must respond to that, because I know the equation must remain true (someone else figured that out). But I admit, I am not totally sure of the processes that occur to make that equation true.
"A few important facts to note in analyzing this problem. 1. Beer bottles/cans and soda bottles/cans are pressurized. 2. They all contain solutes in the solvent, water. 3. Both contain the solute CO2, carbon dioxide. Most solutes will lower the freezing point of solvents when they are combined into a homogeneous mixture. In this case, we have carbon dioxide, the solute, dissolved into water, the solvent. Dissolved carbon dioxide in water will, in fact, lower the freezing point of the solution below 0 C. For beer, there are a few more solutes than carbon dioxide such as alcohol and various salts, but they all act to lower the freezing point of the solution relative to that of water. I read that -0.42 * (percent alcohol by volume) degrees C is accurate. That is, 1 percent of alcohol dissolved in water will lower the freezing point by 0.42 C and the relationship is linear. (I won't really back this up because I didn't get access to the journal article that finds this. The information is out there, though.) That said, the pressurized bottles and cans keep the carbon dioxide in the solution as the bottles and cans are cooled. This in turn lowers the freezing point of the solution below that of water 0 C. For cream soda, it's about -10 C. If the freezer is cool enough, this solution will freeze too. But since most household freezers are kept around 0 C, this tends not to happen. When the bottle is opened, there is a pressure differential between the outside environment and inside the bottle. Typically bottles are pressurized around 5 atmospheres (http://www.newton.dep.anl.gov/askasci/gen01/gen01625.htm). So as the pressure inside the bottle equilibrates with the environment, it lowers, thereby releasing carbon dioxide from the solution.* This has a three-pronged effect. (1) First dissolved solute leaves the solution thereby *raising* its freezing temperature. (2) Second the gaseous bubbles of carbon dioxide forming in the solution expand adiabatically (to very good approximation) and under a constant pressure for the solution. Therefore, the escaping gas bubbles temperatures increase, while the solution cools. (T_initial/V_initial = T_final/V_final) (3) Thirdly, the escaping bubbles agitate the now supercooled solution providing for nucleation sites for crystal growth.** *This is basic chemistry. If a gas is in contact with an incompressible liquid, and the pressure on the gas is increased, more gas is going to be able to stay in solution with the liquid at equilibrium. **This probably warrants more explanation. A solution is called supercooled when its temperature is below its freezing point yet remains a liquid. Similarly, a solution is called superheated when its temperature is above its boiling point yet still a liquid. The beer or soda is essentially supercooled after the carbon dioxide leaves the solution and it doesn't freeze. All crystallization processes (of which water freezing is one) require a nucleation point; some place to begin. The carbon dioxide bubbles leaving solution are generating these nucleation points for crystal growth. Suspended particles in solution can provide nucleation sites, but these tend not to be present in soda and beer. (http://en.wikipedia.org/wiki/Nucleation) When just shaking the can or bottle without having opened it, the agitation increases the entropy of the solution thereby releasing carbon dioxide sufficiently so that (1), (2), and (3) may also occur. Lastly, I used the ideal gas law PV = nRT and the fact that the beer and soda are very good approximations to incompressible fluids to verify this. I believe for water it takes 135 atm to lower its freezing point by 1 C, so incompressible. " So....uh....there you go.
It was CO2 coming out of solution and clinging to the ice crystals, normally the only surface for the bubbles to cling to is the side of the can, but with the additional surface of the ice crystals, enough bubbles can remain submerged to increase the volume enough to reach the top of the can
The liquid was likely at or below the nominal freezing point for beer, and the rapid adiabatic expansion dropped the temperature enough to form ice crystals throughout the mixture. Water ice is one of the few substances with a higher specific volume than it's liquid state at the same temperature, by about 10%. If the can was nearly full as you say, the ice formation would push foam and liquid beer ...mostly alcohol, out the top. An old way to concentrate alcohol was to slush wine in the winter and discard the ice. Other energy effects would be the transfer of the strain energy of the can walls and compressed liquid to kinetic energy of the escaping gases. The elastic expansion of the liquid would certainly be a negligible term for any system using 0.030 aluminum walled pressure vessels with flat ends, though. Another alternative, more of a chemical reaction, would be if the process of separating the H2O from the alcohol in solution is an endothermic process, but that's not in the Mayor's line. Ask a chemical engineer about that one. - - - Updated - - - Good observation.
Wow! That's very interesting! I'm definitely going to keep this bit in mind when I start brewing my own alcohol next year! speaking of that method, do you know if that did anything significant to the flavor?
I once had a bad fridge with a broken thermostat. It would sometimes freeze my sodas. The soda would look fine when you took it out of the fridge, but then you opened the bottle, it would flash-freeze from the top down until you where standing there with a solid frozen coke in your hand like an idiot. When you open the soda/beer the CO2 escapes and that lowers the pressure in the bottle. That in turn lowers freezing point of the water, allowing it to solidify. It could also just be CO2 comming out of the water solution (fizzing out) and instead of bubbling up like normal, it is trapped and helps to float the ice flakes.
