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Name: Samantha
Status: student
Grade: 9-12
Location:
Date: October 2007

Question:
Can you cook a egg in a cold beaker of water that is boiling inside a vacuum?



Replies:
Nope. You could boil it for days at room temperature, and all it would do is grow deadly bacteria inside. Same as it does sitting on the kitchen counter. It takes a specific high temperature, measured in degrees C, to kill germs or make the runny egg-white solidify.

The boiling action of water around an egg is merely an easy accurate way to get a certain temperature that happens to work pretty well for our cooking. It only works repeatably because most of us live in 14.7 psi pressure. It also helps guarantee the temperature won't go higher and burn the part of the food closer to the burner.

Temperature regulation by boiling goes like this:

- If the water is lower than 100C, the heat flowing in from the burner causes the water to heat up towards 100C.

- If the water is 100C, all the heat flowing in goes to evaporating some water (as boiling bubbles), and no increase in temperature occurs. The bubbles stir the water pretty well too.

- If the temperature has somehow reached 102C, part of the water erupts into steam thereby promptly cooling the remaining water right back down to 100C. The eruption is of course quite dangerous because of the 100C water it throws around.

For altitudes higher than sea-level, substitute a temperature lower than 100C.

Boiled eggs at sea-level cook normally. Boiled eggs at 8000 foot altitude cook slower. Boiled eggs at 100,000 feet probably don't cook at all. (But I don't think anybody's ever tried exactly that.)

Jim Swenson


Hello,

The answer to your question is no.

What cooks an egg is heat, however you provide the heat. You can cook an egg under the Sun, in a stove, on a grill, etc. You can also cook eggs in a pot of water at temperatures well below the boiling temperature of about ~ 100 ?C. It just takes longer to cook. If you cook it with water that is boiling hot, it cooks faster.

So, it is not boiling that cooks the egg. It is the heat transfered from the hot water to the egg that cooks it. As you know, there are many liquids that boil well below the freezing point. So, an egg in such liquids (for example, liquid nitrogen) actually freezes instead of being cooked.

Ali Khounsary, Ph.D.
Argonne National Laboratory


Cooking is a chemical reaction that happens above a certain temperature. For example, an egg in the refrigerator will never cook no matter how long it is left there.

Water boils at a lower temperature as air pressure falls because boiling occurs when water is hot enough to turn to a gas despite the outside pressure. That's why some cake mixes have "high altitude" directions; folks living the mountains cook in pressure cookers and tea or coffee on airplanes are never really hot.

It goes the other way, too. The higher the air pressure, the hotter the water must be before it boils. You would have a better chance of cooking your egg in an undersea habitat (high pressure) in water that was not actually boiling.

Bob Avakian
Oklahoma State University - Okmulgee Campus


Samantha,

This is an interesting question! The answer is no, you cannot cook the egg. When we cook an egg in the open atmosphere, we apply heat and it is the application of heat that does the cooking, not the fact that it is boiling. The vapor pressure of the water is related to the boiling point of water and is also related to the atmospheric pressure. In Denver, for instance, you have to cook an egg much longer because water boils at a lower temperature. This is because Denver is 1 mile above sea level and since the atmosphere is thinner, water will boil at a lower temperature. Because cooking is performed by applying heat to a particular food, the amount of heat matters. So if your water boils at, let's say, half the temperature (50C instead of 100C), then you would need a much longer cooking time to compensate for the lower temperature.

Now if we bring in a vacuum, the vapor pressure is very low and will approach zero. This makes the water boil even though there is no heat applied. Eventually the evaporation of the water will chill the water down enough so that in a vacuum the water will freeze if outside heat is not applied. So if you cannot cook an egg at room temperature, you certainly can't cook an egg in ice ;) The main concept here is that it is heat that cooks, not boiling.

Matt Voss


Proteins, like those in eggs, are like carefully coiled up pieces of yarn. Cooking egg proteins means adding enough heat to them that the yard uncoils (scientists call this 'denaturing' the proteins). When the egg proteins uncoil, they tangle up on each other and form the solid matrix that you know as a cooked egg.

If you lower the pressure around the egg, but do not raise the temperature, the water will 'boil', but it will not be adding heat to the egg. Therefore, the proteins will not 'cook'.

Many liquids, as you probably know, will gradually evaporate away if left out. This is because individual molecules of the liquid leave and become gas. These gas molecules that come from the liquid exert a measurable air pressure. If you put a liquid inside a vacuum vessel, then closed off the vacuum, after some time, you could measure some pressure in the vessel. This is called "partial pressure". The more volatile the liquid (volatile means easier to evaporate), the higher its partial pressure. When the partial pressure of the liquid is the same as the ambient pressure, the liquid boils. Thus, the partial pressure of water at 100C is 1atm. If you lower the ambient pressure, say to 0.9atm, then the water will 'boil' at a lower temperature. If you lower the pressure enough, water will boil at room temperature.

Pressure can denature proteins too, but usually it's very high pressures. I haven't heard of low pressures denaturing proteins. If you cracked the egg first, I would guess that would not affect the egg proteins too much -- except that they would dry out in the vacuum pretty quickly.

You may know that egg shells are gas-permeable. They won't leak liquid, but gas molecules can go through. Egg have a little gas-filled sac in them too. If you change air pressure slowly, the egg can equilibrate (make equal on both sides) the air pressure. However, if you put an egg in a vacuum very quickly, I am not sure what would happen. Would the air pocket expand and crack the egg? I'm not sure. Maybe you can try it. Reply back to let me know!

Hope this helps,

Burr



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