Warm water freezes（结冰） 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 a Canadian scientist George Kill proved the English professor was right. Dr Kill filled an open oil pail(桶) with cold water. He filled another with warm water. He put both in the same low temperature. The warm water froze first. The lack of covers on the pails is the secret. Some of the warm water changed into vapor. This meant that less of the warm water was left to be frozen. And so the warm water froze faster than the cold water even though it had a greater temperature drop to make. 小题1:Hundreds of years ago, Sir Francis Bacon found _______. A．the temperature of warm water drops faster than that of cold water B．warm water is heavier than cold water C．warm water has the same temperature as cold water D．warm water is not as useful as cold water 小题2:What Sir Francis Bacon said was right, but people didn't believe him until _______. A．late in the 19th century B．early in the 20th century C．three years ago D．late in the 20th century 小题3:Leave a pail with warm water and another pail with cold water in the same low temperature, you’ll find that _______. A．cold water freezes first B．warm water turns into ice before cold water C．warm water and cold water freeze at the same time D．much of cold water is changed into air. 小题4:Why does warm water freeze first in the same freezing weather? A．Because some of the warm water turns to vapor, the amount(数量) becomes less than that of cold water. B．Because warm water is lighter than cold water. C．Because the temperature of warm water is lower than that of cold water. D．Because cold water freezes with more difficulty than warm water.