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  #11  
Old 11-29-2007, 01:32 AM
madnak madnak is offline
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Default Re: Why does hot water clean dishes better than cold?

The faster molecules bounce around, the more room there is for mixing, the less likely they are to clump together, the more force they have when they collide (and the more likely they are to knock one another loose), etc. And by adding energy to the system, you can make bonds break and increase the likelihood of reactions that might help the cleaning process.
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  #12  
Old 11-29-2007, 01:44 AM
Nielsio Nielsio is offline
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Default Re: Why does hot water clean dishes better than cold?

Think about this: when your food is hot and moist after it is cooked, it doesn't stick to your plate amirite? So it cools, dries and it sticks. How could we possibly get it off? I know: hot water. BAM.
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  #13  
Old 11-29-2007, 02:26 AM
furyshade furyshade is offline
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Default Re: Why does hot water clean dishes better than cold?

[ QUOTE ]
Think about this: when your food is hot and moist after it is cooked, it doesn't stick to your plate amirite? So it cools, dries and it sticks. How could we possibly get it off? I know: hot water. BAM.

[/ QUOTE ]

you dun stole my word-thoughts
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  #14  
Old 11-29-2007, 05:44 AM
Lestat Lestat is offline
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Default Re: Why does hot water clean dishes better than cold?

[ QUOTE ]
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.

[/ QUOTE ]

Heat kills germs AND dissolves food substances better than cold or moderate temperatures.
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  #15  
Old 11-29-2007, 07:17 AM
tshort tshort is offline
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Default 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!
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  #16  
Old 11-29-2007, 07:59 AM
Neuge Neuge is offline
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Default 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.
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  #17  
Old 11-29-2007, 06:20 PM
Jetboy2 Jetboy2 is offline
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Default Re: Why does hot water clean dishes better than cold?

Hi,

Try a simple experiment with your niece. It'll be fun, and she'll love it. And you didn't say the age of your niece, but I'm assuming pretty young, considering the question.

Take 4 glass containers. Put hot tap water in 2 of them and cold tap water in the other 2.

Now for the other ingredients. 2 equal pats of butter/margarine and 2 teaspoons of sugar.

So, put 1 pat of the butter into one of the "hot water" containers and 1 teaspoon of sugar into the other "hot water" container. Likewise, put the same into the "cold water" containers. See what happens.

(You could also add 2 more containers where you add detergent to both the hot and cold water.)

Anyway, little kids usually don't really care about explanations of molecular energy levels and whatnot. And I think that if you do this experiment with her; she'll no doubt, figure out the idea of why hot water works better for washing dishes.

The folks here can surely provide the physics/chemistry of how it works....

jb
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  #18  
Old 11-29-2007, 06:36 PM
Borodog Borodog is offline
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Default 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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  #19  
Old 11-29-2007, 08:27 PM
Jetboy2 Jetboy2 is offline
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Default Re: Why does hot water clean dishes better than cold?

You guys are so very smart, yet failed to help the original poster with the question.

You did manage to kiss each other's ass though....
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  #20  
Old 11-29-2007, 09:28 PM
Jetboy2 Jetboy2 is offline
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Default Re: Why does hot water clean dishes better than cold?

[ QUOTE ]

Heat kills germs AND dissolves food substances better than cold or moderate temperatures.

[/ QUOTE ]

This is partially correct. Enough heat kills germs. Less heat can actually "grow" germs!

"Heat" is relative.
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