Watermelon remains cool even after long time removed from refidgerator
the water inside helps it to cool
this due to specific heat of water in it

due to vegetable and other ingredients in it like onion etc 
it seems to be cool out but
while eating the ingredients in it are HOT

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It is used as car radiotors water is pumped through the channels in the engine block to absorb heat water is used as a cooling agent because it has high specific heat the hot water flows up to the radiotor and is cooled by the air flows to the fins of the radiators the cool water again goes back to the engine capture heat and this cycle is repeated continuosly .it is also used as thermal radiators ,cooking utsensils