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Thread: Chemical reactions for freezing water multiple times

  1. #1 Chemical reactions for freezing water multiple times 
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    Hi! I am looking into chemical reactions that would cause water to freeze faster. The water would not be consumed but could come into contact with skin in mist form in emergency situaitons. The freezing process can be assisted by a power source of approximately 120 Watts. The limitation I have is that the ice must also melt quickly (within 10 minutes) and be able to maintain the same qualities without creating additional reactions.

    Regards, Elisabet


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  3. #2  
    exchemist
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    Quote Originally Posted by ElisabetJ View Post
    Hi! I am looking into chemical reactions that would cause water to freeze faster. The water would not be consumed but could come into contact with skin in mist form in emergency situaitons. The freezing process can be assisted by a power source of approximately 120 Watts. The limitation I have is that the ice must also melt quickly (within 10 minutes) and be able to maintain the same qualities without creating additional reactions.

    Regards, Elisabet
    I'm afraid this is not very clear. Water freezes when enough heat is removed from it for it to first reach its freezing point and then for Latent Heat of Freezing to be extracted from it. How do you envisage that a chemical process could help to extract this heat?


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  4. #3  
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by ElisabetJ View Post
    Hi! I am looking into chemical reactions that would cause water to freeze faster. The water would not be consumed but could come into contact with skin in mist form in emergency situaitons. The freezing process can be assisted by a power source of approximately 120 Watts. The limitation I have is that the ice must also melt quickly (within 10 minutes) and be able to maintain the same qualities without creating additional reactions.

    Regards, Elisabet
    I'm afraid this is not very clear. Water freezes when enough heat is removed from it for it to first reach its freezing point and then for Latent Heat of Freezing to be extracted from it. How do you envisage that a chemical process could help to extract this heat?
    Apologies for this, chemistry is not my expert area thus my cry for help What I am trying to ask is, will adding certain components to water make it freeze quicker in a refrigeration system? And if that substance is ultimately melted to a liquid state and frozen again, would it still freeze quickly?
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  5. #4  
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    Quote Originally Posted by ElisabetJ View Post
    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by ElisabetJ View Post
    Hi! I am looking into chemical reactions that would cause water to freeze faster. The water would not be consumed but could come into contact with skin in mist form in emergency situaitons. The freezing process can be assisted by a power source of approximately 120 Watts. The limitation I have is that the ice must also melt quickly (within 10 minutes) and be able to maintain the same qualities without creating additional reactions.

    Regards, Elisabet


    I'm afraid this is not very clear. Water freezes when enough heat is removed from it for it to first reach its freezing point and then for Latent Heat of Freezing to be extracted from it. How do you envisage that a chemical process could help to extract this heat?
    Apologies for this, chemistry is not my expert area thus my cry for help What I am trying to ask is, will adding certain components to water make it freeze quicker in a refrigeration system? And if that substance is ultimately melted to a liquid state and frozen again, would it still freeze quickly?
    OK. When you say, "quicker", what do you have in mind? Do you, for example, mean you want it to freeze at a different temperature from 0C, higher or lower? Or do you mean you want to reduce its Latent Heat so that you do not need to extract so much heat to make it freeze?

    As far as I am aware, anything you add to it will depress its freezing point, not elevate it.

    I think I would expect impurities to decrease Latent Heat of Fusion somewhat, but probably not by much. If you want a substance that releases less heat when it freezes, you may need to consider something other than water.
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  6. #5  
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by ElisabetJ View Post
    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by ElisabetJ View Post
    Hi! I am looking into chemical reactions that would cause water to freeze faster. The water would not be consumed but could come into contact with skin in mist form in emergency situaitons. The freezing process can be assisted by a power source of approximately 120 Watts. The limitation I have is that the ice must also melt quickly (within 10 minutes) and be able to maintain the same qualities without creating additional reactions.

    Regards, Elisabet


    I'm afraid this is not very clear. Water freezes when enough heat is removed from it for it to first reach its freezing point and then for Latent Heat of Freezing to be extracted from it. How do you envisage that a chemical process could help to extract this heat?
    Apologies for this, chemistry is not my expert area thus my cry for help What I am trying to ask is, will adding certain components to water make it freeze quicker in a refrigeration system? And if that substance is ultimately melted to a liquid state and frozen again, would it still freeze quickly?
    OK. When you say, "quicker", what do you have in mind? Do you, for example, mean you want it to freeze at a different temperature from 0C, higher or lower? Or do you mean you want to reduce its Latent Heat so that you do not need to extract so much heat to make it freeze?

    As far as I am aware, anything you add to it will depress its freezing point, not elevate it.

    I think I would expect impurities to decrease Latent Heat of Fusion somewhat, but probably not by much. If you want a substance that releases less heat when it freezes, you may need to consider something other than water.
    By quicker, I suppose I mean I want to reduce its Latent Heat and thus the amount of heat needed to be extracted. I'm such a visual person, so maybe a concrete example would be better (for me). I put a ice tray of regular distilled water at room temperature in my freezer, and it takes X amount of time to freeze. The only way to reduce X is to either change the temperature before starting to freeze it or decrease the amount of water which needs to be freezed. There is nothing that will reduce X without changing the orignal temperature or volume factors?

    There are perhaps other substances than water that I should consider if I'm looking to recreate something like an icepack for sports injuries?

    (Science is cool when you understand it B) )
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  7. #6  
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    Quote Originally Posted by ElisabetJ View Post
    By quicker, I suppose I mean I want to reduce its Latent Heat and thus the amount of heat needed to be extracted. I'm such a visual person, so maybe a concrete example would be better (for me). I put a ice tray of regular distilled water at room temperature in my freezer, and it takes X amount of time to freeze. The only way to reduce X is to either change the temperature before starting to freeze it or decrease the amount of water which needs to be freezed. There is nothing that will reduce X without changing the orignal temperature or volume factors?

    There are perhaps other substances than water that I should consider if I'm looking to recreate something like an icepack for sports injuries?

    (Science is cool when you understand it B) )
    Ah, something for sports injuries? Well in that case, you have to realise that if you choose something with lower Latent Heat of Fusion, then it will not have such a prolonged cooling effect on the injury. Water has a very high Latent Heat, which means it takes a lot of heat to melt it, so it melts slowly and stays cool for a long time. If you went for something with a lesser Latent Heat of Fusion it would stop working more quickly. Would that be OK or would it defeat the object of your idea?
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    Are you looking for something like this Instant cold pack - Wikipedia, the free encyclopedia ?
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by ElisabetJ View Post
    By quicker, I suppose I mean I want to reduce its Latent Heat and thus the amount of heat needed to be extracted. I'm such a visual person, so maybe a concrete example would be better (for me). I put a ice tray of regular distilled water at room temperature in my freezer, and it takes X amount of time to freeze. The only way to reduce X is to either change the temperature before starting to freeze it or decrease the amount of water which needs to be freezed. There is nothing that will reduce X without changing the orignal temperature or volume factors?

    There are perhaps other substances than water that I should consider if I'm looking to recreate something like an icepack for sports injuries?

    (Science is cool when you understand it B) )
    Ah, something for sports injuries? Well in that case, you have to realise that if you choose something with lower Latent Heat of Fusion, then it will not have such a prolonged cooling effect on the injury. Water has a very high Latent Heat, which means it takes a lot of heat to melt it, so it melts slowly and stays cool for a long time. If you went for something with a lesser Latent Heat of Fusion it would stop working more quickly. Would that be OK or would it defeat the object of your idea?
    Yes, the cooling effect would be optimal if it lasted 10 to 15 minutes, with the cooling temp being below room temp.
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    Quote Originally Posted by PhDemon View Post
    Are you looking for something like this Instant cold pack - Wikipedia, the free encyclopedia ?
    Well yes, in concept but I was also wondering what alternatives there were for a solution of water and one compound.
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    Then you need something with a large positive enthalpy of solution, off the top of my head other than the examples in the wiki link potassium chlorate is the only one I can think of, but there are more in this table: http://sites.chem.colostate.edu/dive...ectrolytes.pdf
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    Thank you both for the replies!
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    Supersaturated solution of Ammonium cation and Chloride, Sulfate anion ect.. Tap the beaker, and the water/solute solution will turn ice cold. You can boil it and it will go back to supersaturated state (if you carefully cool it down), looking like pure water as long as its not significantly disturbed. Tap it again and it should have the same effect each and everytime.
    Last edited by AndresKiani; July 12th, 2014 at 12:51 PM.
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by ElisabetJ View Post
    By quicker, I suppose I mean I want to reduce its Latent Heat and thus the amount of heat needed to be extracted. I'm such a visual person, so maybe a concrete example would be better (for me). I put a ice tray of regular distilled water at room temperature in my freezer, and it takes X amount of time to freeze. The only way to reduce X is to either change the temperature before starting to freeze it or decrease the amount of water which needs to be freezed. There is nothing that will reduce X without changing the orignal temperature or volume factors?

    There are perhaps other substances than water that I should consider if I'm looking to recreate something like an icepack for sports injuries?

    (Science is cool when you understand it B) )
    Ah, something for sports injuries? Well in that case, you have to realise that if you choose something with lower Latent Heat of Fusion, then it will not have such a prolonged cooling effect on the injury. Water has a very high Latent Heat, which means it takes a lot of heat to melt it, so it melts slowly and stays cool for a long time. If you went for something with a lesser Latent Heat of Fusion it would stop working more quickly. Would that be OK or would it defeat the object of your idea?
    there are always found materials in the chemical shops for doing it by commercial as default. Sports injuries uses some of the activators which reduce substance energy to increase reaction speed.
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    Quote Originally Posted by ElisabetJ View Post
    Quote Originally Posted by PhDemon View Post
    Are you looking for something like this Instant cold pack - Wikipedia, the free encyclopedia ?
    Well yes, in concept but I was also wondering what alternatives there were for a solution of water and one compound.
    This principle is used in aerosol cans for cooling. A mixture of an oil, that does not evaporate, and methylbutane or something with a boiling point from around 15-30 degrees celcius. Why use water?
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