On Sat, 25 Jun 2011 18:30:21 +1000, atec77 > wrote:

>On 25/06/2011 5:08 PM, dsi1 wrote:
>> On Jun 24, 7:16 pm, (Steve Pope) wrote:
>>> Jerry > wrote:
>>>
>>>>> On Fri, 24 Jun 2011 02:54:58 -0400, >
>>>>> wrote:
>>>
>>>>>> My father, who WAS a physicist, was not convinced that a covered pot
>>>>>> would boil faster than an uncovered pot.

Your father was no physicist.

>>>> I can't see Cheryl's post, so I'll answer here. A covered pot boils
>>>> faster because the cover prevents the faster molecules from escaping.

That's true.

>> This makes a lot of sense if most of the heat loss occurs when the
>> water changes to steam and escapes into the room.

Water heated in an unpressureized vessel does not become steam, it
becomes water vapor.

>>Covering the pot
>> recovers some of the latent heat by condensing it back into liquid
>> water.

This is true.

Actually the lid reflects radiant heat energy back into the water
rather than from escaping to the atmosphere, prevents heated air
molecules from escaping, and returns heated condensate... without the
lid water evaporates and much more rapidly as temperature rises... and
evaporation actually has a cooling effect, so as the water temperature
rises so does the rate of cooling from evaporation... this is why an
uncovered pot seems to take forever to boil... the rate of rise
actually slows as the water approaches boil. All else equal a covered
pot will always reach the boil faster. And a lid prevents you from
watching and every physicist knows a watched pot never boils. This is
all summed up by observing what occurs by folks who have attempted to
cook pasta with the lid on... the pot has a macaroni orgasm... clear
viscous fluid erupts all over the pot, the stove, even can dribble
onto the floor.