Why does the evaporation of sweat cool your body?
It takes energy to change water into vapour so the sweat is taking what would have been heat energy and using that energy to vapourize the water instead :) therefore you cool down
Some surgical procedures involve lowering a patient's body temperature during periods when blood flow must be?
This will slow down metabolism, since enzymatic reactions do not proceed as quickly under cooler conditions.
At what temperature would humans freeze to death within less than five minutes?
I knew a lady who fell down an icey cliff and was stuck at the bottom frozen wet and unable to move.She said she lost about 3 stones in weight in the space of a few hours. So the body really does pull out all the stops for survival.In her case she was probably minutes away from death when she was rescued.It would probably depend on somones build too as to how long they can survive in freezing temperatures. A very thin person might go before a stout person with greater reserves.Another story was of a woman who was walking home in the snow and she got stuck in a blizzard. She collapsed and lay down in the road.Search teams eventually found her. When they did she was frozen solid. Her body was completely covered in ice and totally rigid.They took her back to hospital and set about thawing her. They did it gradually and to everyones amazement she woke up and was perfectly OK.It's amazing how the body can survive, her system must have gone into a hibernating mode to protect her.