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NickyTwoHats
2,044 posts
111 months
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Try a little thought experiment.
Take "hot water" cool it.
After some time it will reach the temperature of the "cool water"
Then it will get even colder and eventually freeze.
So how can the hot water freeze in less time than the cool?
N2H
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balders118
Original Poster
3,285 posts
38 months
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NickyTwoHats said: Try a little thought experiment.
Take "hot water" cool it.
After some time it will reach the temperature of the "cool water"
Then it will get even colder and eventually freeze.
So how can the hot water freeze in less time than the cool?
N2H Google "mpemba effect". It does happen, but the cause isn't knows and conditions seem impossible to replictae reliably (except for using different types of water).
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Alpinestars
707 posts
114 months
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Pure water freezes at 0 degrees, and "pollutants" reduce the freezing point don't they? Therefore like for like, colder water freezes quicker, but when comparing warm distilled water to say tap water, the tap water may take longer to freeze as its freezing point will be lower.
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Flibble
1,089 posts
51 months
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Alpinestars said: Pure water freezes at 0 degrees, and "pollutants" reduce the freezing point don't they? Therefore like for like, colder water freezes quicker, but when comparing warm distilled water to say tap water, the tap water may take longer to freeze as its freezing point will be lower. The difference in freezing point between tap water and distilled water is negligible, there's plenty of reasons put forward for the mpemba effect, but different composition of the water is not one of them (the effect occurs even using the same water in both cases).
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wormburner
6,425 posts
123 months
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Leave the peas on the side for a while first. Or use them to chill a drink.
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EggsBenedict
352 posts
44 months
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I think you're right about their being an optimum amount of water.
Too much and the kettle takes longer to boil in the first place
Too little and the energy taken out of the water to bring the peas into equilibrium with the water will mean that the water will take more time to boil on the hob (which as has been noted is less efficient at heating water than a kettle).
Peas are mostly water, so I suspect that you could give a reasonable approximation of how long it would take for them to get from one temperature to another by heating the equivalent mass of water?
It's odd you ask, though, as I have been through this mental calisthenic myself. My conclusion is that it's the pan that takes a decent amount of time/energy to warm up (most of ours are thick bottomed to withstand use on an Aga). So if I'm cooking peas on the hob, then I (1) put the kettle on, (2) put the pan on the hob, (3) pour a little water from the kettle to the pan (they're next to each other in our house) so that the pan doesn't get damaged, (4) wait for kettle to boil, (5) bung peas into pan, (6) pour water over.
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balders118
Original Poster
3,285 posts
38 months
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EggsBenedict said: I think you're right about their being an optimum amount of water.
Too much and the kettle takes longer to boil in the first place
Too little and the energy taken out of the water to bring the peas into equilibrium with the water will mean that the water will take more time to boil on the hob (which as has been noted is less efficient at heating water than a kettle).
Peas are mostly water, so I suspect that you could give a reasonable approximation of how long it would take for them to get from one temperature to another by heating the equivalent mass of water?
It's odd you ask, though, as I have been through this mental calisthenic myself. My conclusion is that it's the pan that takes a decent amount of time/energy to warm up (most of ours are thick bottomed to withstand use on an Aga). So if I'm cooking peas on the hob, then I (1) put the kettle on, (2) put the pan on the hob, (3) pour a little water from the kettle to the pan (they're next to each other in our house) so that the pan doesn't get damaged, (4) wait for kettle to boil, (5) bung peas into pan, (6) pour water over.  I'm glad I'm not the only one that thinks like this. I have also pre-heated the pan too, although I wonder whether the wasted heat from the hob before the peas go in reduces the benefit of the smaller cooling effect. Although if you are using an Aga, then it's of no concern.
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RYH64E
3,406 posts
114 months
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If the water was boiling in the first place, and the question is how much energy is needed to return it to boiling after pouring onto frozen peas, then I don't think that the volume of water used affects the result. The cold peas/pan will remove a certain amount of heat from the water and that is the amount that has to be replaced, regardless of volume.
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balders118
Original Poster
3,285 posts
38 months
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RYH64E said: If the water was boiling in the first place, and the question is how much energy is needed to return it to boiling after pouring onto frozen peas, then I don't think that the volume of water used affects the result. The cold peas/pan will remove a certain amount of heat from the water and that is the amount that has to be replaced, regardless of volume. Put like that, it makes a great deal of sense.
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wormburner
6,425 posts
123 months
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balders118 said: Put like that, it makes a great deal of sense. I believe the practical answer is as much a function of the size of the hob and the size of the pan base as it is of the quantity of water.
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0a
8,528 posts
64 months
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balders118 said: LordFlathead said: Off topic and dumbest of all comments relating to peas.. Why don't they explode when you boil them. They contain air and are sealed.  - Something I have thought about for years The outer skin of the pea will be porus  No, LordFlathead has his minions seal his peas for him (with pea-sealant).
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Flibble
1,089 posts
51 months
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0a said: No, LordFlathead has his minions seal his peas for him (with pea-sealant). Are they laminated? 
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RobbyJ
212 posts
92 months
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I usually fill the pan full of frozen peas with cold water first, then drain, then add the boiling water as even room temp water removes quite a bit of the cold temp from the water and as I'm not on a water meter it's technically free. I'm so sad!
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