用“风、树、雨”表达自己获得荣誉、受到表扬时的心情。
一 I failed in the driving test again. Sorry to let you down.
一 How come? I've helped you practice enough.
用燃气灶烧水,燃烧0.5kg的煤气,使50kg的水从20℃升高到70℃.已知水的比热容为4.2×103J/(kg•℃),煤气的热值为4.2×107J/kg.求:
(1)0.5kg煤气完全燃烧放出的热量.
(2)水吸收的热量.
(3)燃气灶烧水的效率.