Warm water freezes (结冻) more quickly than cold water.Sir Fra

Warm water freezes (结冻) more quickly than cold water.Sir Francis Bacon said that almost four hundred years ago.But few people believed him until 1970.In that year Canadian scientist Geoge Kell proved (证明) the English physicist was right.Dr Kell filled one open bowl with cold water.He filled another with warm water.He put both bowls to the same low temperature.The warm water froze(结冰) first.
　　The lack(没有) of covers on the bowls was the secret(秘密).Some of the warm water changed into vapor.(蒸汽) It evaporated(蒸发) into the air.This meant that less of the warm water was left to freeze.And so the warm water froze faster than the cold water.
80.Sir Francis Bacon was ______.
　A.an American scientist 　B.a Canadian scientist
　C.a French scientist 　D.an English scientist
81.Most people didn’t believe Bacon because warm water is ______.
　A.further from freezing temperature than cold water
　B.quicker to evaporate than cold water
　C.able to flow(流) faster than cold water
　D.a little harder than colder water
82.The second paragraph tells why ______.
　A.Sir Bacon and Dr Kell were studying water together
　B.there is a secret inside the water
　C.water freezes in winter
　D.the warm water froze first
83.Warm vapor can’t freeze faster if the bowls are ______.
　A.full 　B.covered 　C.put outside 　D.changed