I think that may be false. I bet 100mls of water would boil faster in an (electric ehu) kettle than in a camping gaz kettle AND I hyopthsise that, as you say Wildy, 100mls would boil at the same speed in a kettle as in a saucepan (with lid) IF the surface area and material of both recepticles is identical.
DH always says that a pan of water will boil quicker without the lid on. I reckon its not true as the heat is retained with the lid, but he says its something to do with the oxygen...I usually shut off then. It may be the same thing with a kettle not getting O2 and taking longer to boil.
And Ochef has just answered all my questions (on the subject of boiling water)
Q. Does water in a covered pan come to a boil faster than in an uncovered pan? Why?
A. Does your head stay warmer when you have a hat on? Mothers everywhere have been telling us for years that 40% to 99% of body heat (the actual number varies depending on which mother is talking) is lost through the head when we don't wear our hats in cold weather. (Perhaps you weren't listening.) But it works just the same with cooking. Without a lid, more of the heat that you're applying at the bottom of the pot escapes at the top. With a lid, the heat collects more quickly, raising the temperature and getting to a faster boil.
Those brave individuals who grill outdoors through the cold winter months have learned this lesson. They are generally obliged to close the lids on their grills in order to collect enough heat to cook their food even though the steaminess caused by the closed lid is a hindrance to great grilling. But do they wear their hats while grilling? We think you can guess the answer.
Now we have a Cobb <punches air> I think we will be roasting chicken in the winter with dh indoors, bareheaded.
On a slight aside I read on here a while back about cooking pasta and rice without contant heat underneath. So you stick the rie/pasta in , bring to the boil, lid on, turn heat off. Leave for normal cooking times. works a treat.
I thought I'd try it chez camping gaz (to save on the gas) and you know it worked. i brought it back to the boli again half way through but it cooked fine, adding on maybe 5 mins to the cooking time.