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Kitchen condensation

  1. Jul 28, 2015 #1
    So I'm having an argument.. and I just can't explain this in a way that manages to be convincing.

    So there are two pots in question:
    One is a special pot made out of a supposedly special material, and has a very tight lid. Once the lid is on, I observe that if you simply poured water on the top of the pot, the water would end up sealing the bowl tight. The lid was designed in such a way.

    The other pot is just some standard pot. Apparently, these standard pots burn when left unattended over fire, and this "special" one, does not, or at least, the charcoal parts can be rubbed off.

    This is the problem:
    Apparently water can be extracted from foods with the special one. A carrot and egg go in. No other water. Cook it. The egg goes from uncooked to cooked. The carrot is nice and puffy and well-cooked to an edible state.
    When everything is over, there is lots of water which wasn't there in the first place.
    Apparently the carrot has created water; this pot extracts liquid from foods.

    It's my strong opinion that this is rediculous. The water that is seen after all the (initially very dry) cooking is obviously extracted from the air. However, with regards to how this condensation, I'm not sure how to explain- I believe what's going on is that the humidity in the air is turned into steam. Being an enclosed pot, the steam simply condenses?

    But other than that, can someone please provide a full scientific explanation of what's going on, when you put a dry carrot, an uncooked egg and nothing else into a pot and seal it, then find more water in the pot when you're done cooking? It's not an airtight seal, mind you- Only the weight of the lid keeps the air in. Steam regularly escapes from the pot.
     
  2. jcsd
  3. Jul 28, 2015 #2

    Bandersnatch

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    When you heat up gas, you reduce it's propensity for condensation, not the other way around, so I'm inclined to agree with the pot here.
     
  4. Jul 28, 2015 #3

    Bandersnatch

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    Here's something more in-depth about how condensation works:

    The difference between gas and liquid is that the molecules in a gas move fast enough not to stick together when they collide.

    Imagine a pool of water in an evacuated box. The kinetic energy associated with the temperature of the water makes its molecules wiggle and bounce. There's an absurdly large number of such molecules in each gram of water, and they collide chaotically, so every now and then there will be one or another that gets enough energy from a collision to unstick itself from the rest and fly away into the vacuum. After some time, that is no longer a vacuum, as water vapour molecules (steam) have created a gaseous atmosphere. (A side note here - steam is transparent; the white thing we tend to call steam in a kitchen is actually the part of it that has just condensed)
    This is evaporation, and it transfers molecules from liquid to gas (change of state).

    The steam molecules floating above the pool of water will every now and then collide with each other. Every now and then, one or two of them will lose enough energy in a collision to stick together, or stick to the walls, or hit the pool and not bounce back. The more molecules are there in a gas in a given volume, the more likely it is going to happen. This effect is the condensation, and it acts to remove molecules from gas and add them to the liquid state.

    The two effects act simultaneously, and at some point reach a balance between the number of molecules that leave the liquid and those that leave gas. The two states are in an equilibrium.

    However, if you change the temperature (or pressure, or volume of the box, but let's focus on temperature) of the box and its contents, you'll make the molecules move faster, and their increased energy will make the steam molecules less likely to stick together, and the water molecules more likely to get a boost out of the liquid state.
    This means, that as you increase temperature, you increase the amount of molecules that can exist in the gaseous state without condensation.

    The above means, that in a hot environment of tropics, you can have very high humidity in air, while in cold environment of the arctic the air will always be dry. It's just impossible to 'fit in' too many water vapour molecules in a cold air before it starts condensing as frost or snow.

    When you put your pot on the stove and seal it so that very little air may get in, the only water vapour present is that which was trapped with the air, and the only way to extract this vapour is to cool the whole pot, unless the air was already oversaturated - in which case you'd observe copious condensation everywhere outside the pot as well.

    If you heat the pot, you are increasing the capacity of the air in it to hold water vapour. Any source of water that you will place in the pot will share its water content with the air, until the point of saturation where it begins to condense. If you then take the pot off the stove, you reduce its temperature, reducing the capacity of air within to hold steam, making even more of the vapour condense. But unless you cool the pot to below the original temperature, you won't be able to make the air dryer than it was initially. Wherever the water comes from, it is not the air that was trapped in the pot.

    By the way, a carrot could very well be such a source of water, considering how ~87% of its weight is water.

    However, you said something about water used for sealing the lid - perhaps that is your source?


    We could devise an experiment to determine where does the water come from:
    First, put a carrot in the pot and put it on the stove. Measure the condensation collected after a set time. You could weight the carrot before and after and compare with the weight of the collected water.
    Next, put an empty pot on the stove with water sealing the lid and see if you find condensation. Compare with your earlier set-up.
    Finally, put the pot on the stove without any water sealing the lid or without anything inside. Is there any condensation? (if there is, I might consider eating my hat)

    Try it! For science!
     
  5. Jul 28, 2015 #4

    russ_watters

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    Cooking extracts water from whatever is being cooked, because heating speeds evaporation and heating a lot causes boiling.

    By the way, it also means you can't seal a pot air or water tight without clamps and an air valve (a pressure cooker).
     
  6. Jul 29, 2015 #5
    But wouldn't this just work with all sorts of pots then?

    The reason I'm opposed to this is because this pot is sold as part of a pyramid scheme's things to sell. I'm opposed to the idea that this stuff could possibly be legitimate.
     
  7. Jul 29, 2015 #6

    Bandersnatch

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    If it's got some sort of system for keeping the moisture inside, a seal better than none at all, then it's neither a new nor an exceptional idea. When you cook e.g. a piece of chicken in the oven, you may just put it on a tray, which would be the equivalent of just placing it in a regular pot. It will lose moisture as it cooks. You may, however, buy a baking bag to enclose the chicken as it cooks, and all the moisture it loses will be retained in the bag, some of it condensing, which altogether keeps the meat moist.

    The main problem with cooking in a pot would be uneven heat transfer through the walls of the pot in contact with food, which normally ends up burning one side before the rest is cooked. Perhaps the pot is made of material with good heat conduction, perhaps they just cook stuff on very low heat. It's hard to guess without seeing it.

    That it may work, though, doesn't mean the pyramid scheme is any less reprehensible, or that the product is not overpriced and overhyped. Just as well, the morally-dubious business model doesn't necessarily mean their product must be fake.
     
  8. Jul 29, 2015 #7

    russ_watters

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    I'm not clear on what the exactly marketing claim is here.
     
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