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#1
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Why does hot water clean dishes better than cold?
My niece asked me - I confidently began answering, then realised i didnt really have a clue.
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#2
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Re: Why does hot water clean dishes better than cold?
Actually heat kills germs bunny. Utensils in particular go into our mouths and the typical human mouth has 30+ bacterias in it plus cold germs, etc.
A dishwasher is particularly good because the intensity of the heat will kill more germs i.e. sterilization occurs. |
#3
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Re: Why does hot water clean dishes better than cold?
I doubt that a dishwasher is hot enough to kill many bacteria. It's not like it's an autoclave.
Higher internal energy means that it is easier for the water molecules to penetrate food particles on the dishes and break them up. That's my guess, anyway. |
#4
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Re: Why does hot water clean dishes better than cold?
Solubility generally goes up as temperature rises. Water is polar and dissolves polar molecules. Soap is part polar part non-polar so it dissolves polar grease and washes away with water.
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#5
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Re: Why does hot water clean dishes better than cold?
I suspect it has a lot to do with dissolving the food particles and residue. Much of the grime on plates is water soluble, and as you know, things dissolve quicker in warmer water. Also most of the greasy residue will liquify at the higher temperatures, making it easier to rinse off.
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#6
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Re: Why does hot water clean dishes better than cold?
[ QUOTE ]
I suspect it has a lot to do with dissolving the food particles and residue. Much of the grime on plates is water soluble, and as you know, things dissolve quicker in warmer water. Also most of the greasy residue will liquify at the higher temperatures, making it easier to rinse off. [/ QUOTE ] Most of the grime on plates is NOT water soluble. Most of it is fat and grease. |
#7
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Re: Why does hot water clean dishes better than cold?
ill take a stab:
The kinetic energy of all those hot water molecules is going to dislodge many more dirt particles off of the surface of dishes, when compared with the effect of cold water molecules. Come to think of it, isn't temperature a measure of the root mean square momentum of the particles? |
#8
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Re: Why does hot water clean dishes better than cold?
[ QUOTE ]
That's my guess, anyway. [/ QUOTE ] Borodog, You are going to consult some colleagues on this, right? SMP needs a definitive answer! |
#9
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Re: Why does hot water clean dishes better than cold?
[ QUOTE ]
[ QUOTE ] That's my guess, anyway. [/ QUOTE ] Borodog, You are going to consult some colleagues on this, right? SMP needs a definitive answer! [/ QUOTE ] Believe it or not, SMP has a bigger authority on this than Borodog. [img]/images/graemlins/smile.gif[/img] (not denigrating Boro, it's just that chemical engineers, in general, can answer this type of question better than astrophysicists) There are 3 major reasons hot water works better than cold water in this situation, and all of them have been mentioned in this thread. 1. The biggest factor is that hotter water allows higher concentrations of detergent. That allows more surface interactions between the solid food, detergent and hot water. 2. Hotter water allows more water penetration into the dried food-stuffs on the plate (which again facilitates the surface interactions). 3. Diffusion rates are higher in hotter water. This means detergent molecules that do dissolve a lipid molecule from the dish surface are more easily transported to the bulk liquid. |
#10
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Re: Why does hot water clean dishes better than cold?
[ QUOTE ]
[ QUOTE ] [ QUOTE ] That's my guess, anyway. [/ QUOTE ] Borodog, You are going to consult some colleagues on this, right? SMP needs a definitive answer! [/ QUOTE ] Believe it or not, SMP has a bigger authority on this than Borodog. [img]/images/graemlins/smile.gif[/img] (not denigrating Boro, it's just that chemical engineers, in general, can answer this type of question better than astrophysicists) [/ QUOTE ] Abso-freaking-lutely. There's a reason why I went into astrophysics and not dish soap. |
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