When cooking which part is the hottest, top or bottom of liquids ?

Steam, thats the hottest part in the boiling water.

So when the flame is hottest the steam explodes from the bottom and rises to the top hence food cooks faster at hotter flames though the water temprature never exceeds 100 degrees, the steam bubbles are very hot more than 100 degrees.

We can see some steam bubbles exploding at the bottom but never riseup, thoes bubbles implode back into water due to water pressure, Hence water is hottest at the bottom.

 

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The steam is never above 100c but can get very close to it. The air bubbles in boiling water is just water becoming steam and separating from water. The more "bubbles" there are the hotter the overall temperature of the material in the pan is. Since what you would be cooking is in the pan, things would then be cooked at a higher temperature.

 

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I think it can and is, slightly when the bubble first forms. (Even neglecting the fact that the presure at bottom of pan is slightly more than atmospheric.) This is due to the surface tension and corresponding very high internal presure in the very tiny, just formed bubble.

If the water is very pure and their are no "micro cracks" in the bottom of the pan, even the water in the pan can "supper heat." I.e. be well above 100C.

In this case, say the water is 105C, what will happen is the bubble will initially be 105C also, but as steam at that temperature has much greater pressure than exists even at the bottom of the pan, the bubble will rapidly expand and adibatically cool down to approximately 100C.

Thus, many of you nominating the "steam" as the hottest part of the H2O are wrong, at least with pure,very clean, water. The bubble of steam can easily be 5 degrees C COLDER THAN THE WATER if the water is clean and pure.

 

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When a thermonuclear device is detonated underwater in the Pacific Ocean, the entire ocean doesn't boil, but only that which is closest to the fireball. Instantaneously vaporised, really, with water at lower temperatures the farther away one gets. Your pasta would cook fairly fast at ground zero, and not at all several miles away.

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Ok, now I remember. The temperature can exceed 100C. It is just that at sea level it boils at 100C, where below sea level it can be higher because of the pressure.
The only thing I have to state about the temperature difference is that it will be nominal.

 

so pressure cookers are better.

 

the hottest part is initially the bottom, heat creates pressure on the bottom and so the heat is difussed through the liquid all the way to the top ( as you can see by the rising bubbles). The bubble you see are basically packets of heat; sort of like photons. Because the molecules in liquids are less stationary it takes only a few seconds for the heat to reverb through the entire liquid, so it doesn't matter where you put the peas as the result will be negligible if not indifferent.

 

Pressure cookers can get a water temperature above 100°C. Same basis as autoclaves actually (or vice versa).

 

In various pressuring techniques one can get water up to any temperature (since the boiling point is different in different pressures). Also even if no external heat source the temperature varies inside the water so that some parts can be 100C, that's why water turn into vapour even in room-temperature.

 

has anyone ever superheated water in a pan? one time I was going to cook some pasta, and I noticed that the very surface of teh water was sizeling as if it were on a frying pan, and the whole thing started poiling briskly as soon as I dropped some pasta in. I assume it was superheated, but maybe something else was happening.

 

Technically, it would be Potatoes at the Bottom and Peas on top. This isn't necessarily because of the heat but the fact that it's the natural way the potatoes and peas would seperate to my knowledge.

As Others have perhaps pointed out, Due to the size of potatoe it can be suggested that convection will take longer to cook it to it's centre, in relationship to a pea with has a very small area.

When cooking items with boiling water you are basing the cooking time on the time it takes convection to cook the item thoroughly. With microwaves you have the added waveformation that penetrates a small distance (Distance is dependant on the items mass and type.)

As for where is hotter in a Saucepan, obviously the Bottom and then the sides. This is based on the transition of heat across the saucepans surface, it's then convection from these surfaces that boils water. If you truly want to prove where it's hotter, use a clean pan (thats old) and then put some pasta sauce in there and boil it up, if you don't stir it will stick and burn to the pan. Where it sticks and burns is obviously hotter.

 

Don't forget that 100 degrees is only for pure water. Simply adding salt can raise the boiling point, just as it lowers the freezing point [which is why we dump salt on the road in the winter]. If you dump some salt into a pot of boiling water, it will stop boiling.