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    hello,
    why does it take more energy to boil water then to melt it??
    pls help thankx
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    Melting water? how strange.
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    (Original post by vinny221)
    Melting water? how strange.
    i'm guessing they mean ice-->water....

    i'm no chemist but my guess would be that the natural environment ur trying to do it in contributes towards the melting as room temp is higher than the ice temp... and when trying to boil u r going against the natural environment as it is constantly trying to bring the temp down...

    of course there other factors etc...
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    (Original post by kunalshah101)
    hello,
    why does it take more energy to boil water then to melt it??
    pls help thankx
    If it really takes more energy to boil water than to melt it, then it is because: the standard enthalpy change of fusion of water(ie the energy required to melt a unit mass of water) is smaller than the standard enthalpy change of vapourisation of water(ie the energy required to boil a unit mass of water). That is the basic answer. To get the reason why this is the case, I'll advise you to use google or an A'level chemistry textbook.

    btw, I last did this a long time ago so my answer is probably not the most accurate thing you can find.
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    (Original post by Don Bosco)
    If it really takes more energy to boil water than to melt it, then it is because: the standard enthalpy change of fusion of water(ie the energy required to melt a unit mass of water) is smaller than the standard enthalpy change of vapourisation of water(ie the energy required to boil a unit mass of water). That is the basic answer. To get the reason why this is the case, I'll advise you to use google or an A'level chemistry textbook.

    btw, I last did this a long time ago so my answer is probably not the most accurate thing you can find.
    Does this make water special? Because we usually expect the other way round.
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    it's probably because of the H-bonding

    you might want to do some comparisons on the two enthalpies for H-bonded and non H-bonded compunds

    e.g. alcohols vs ethers
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    I think in ice, the hydrogen bonds are more spaced apart. In water, the hydrogen bonds are much closer and form and reform.
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    I think in ice, the hydrogen bonds are more spaced apart. In water, the hydrogen bonds are much closer and form and reform.

    You're right. This is why water is denser than ice and pipes break in the winter!
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    (Original post by celeritas)
    Does this make water special? Because we usually expect the other way round.
    No that's the way it usually is. The energy to boil a material is almost always higher than the energy to melt it, me thinks. Not sure though.
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    (Original post by Don Bosco)
    No that's the way it usually is. The energy to boil a material is almost always higher than the energy to melt it, me thinks. Not sure though.
    You're correct. http://en.wikipedia.org/wiki/Latent_heat

    But it's kinda counter-intuitative. Right? I would've thought it takes a greater energy to melt the same amount of substance than to boil it.

    But I guess you can argue it takes more energy to boil a substance, as the separation of molecules is much greater.
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    Entropy people!!!

    Look it up in your textbook. Water freezing and ice melting is the example ALWAYS given
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    (Original post by Spacecam)
    Entropy people!!!

    Look it up in your textbook. Water freezing and ice melting is the example ALWAYS given
    What has that to do with the energy required to break bonds? The fact that the molecules are separate results in an increase of entropy.
 
 
 
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