问题
问答题 简答题
何为燃料的发热量？高发热量？低发热量？
答案
参考答案：
1千克煤完全燃烧后所放出的燃烧热叫做他的发热量。高发热量指的是燃料完全燃烧后的燃烧产物冷却到是其中的水蒸气凝结成0摄氏度时的水所放出的热量。低发热量指的是燃料完全燃烧后燃料产物中的水蒸汽冷却到20摄氏度时放出的热量。
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何为燃料的发热量？高发热量？低发热量？
参考答案：
1千克煤完全燃烧后所放出的燃烧热叫做他的发热量。高发热量指的是燃料完全燃烧后的燃烧产物冷却到是其中的水蒸气凝结成0摄氏度时的水所放出的热量。低发热量指的是燃料完全燃烧后燃料产物中的水蒸汽冷却到20摄氏度时放出的热量。
| 阅读理解。 | ||||||||||||
| Big ocean fish have almost been endangered since the start of business fishing in the 1950s. The scientists found that the number of large fish has dropped by 90 percent in the past fifty years. The study took ten years. The researchers collected records from fishing businesses and governments around the world. The magazine Nature published (发表) the findings. The scientists say the common way called longline fishing is especially harmful to large fish. This way includes many fishing lines that are connected (连接) to one boat. If these lines are joined together, they can reach one hundred kilometers. They hold thousands of sharp metal hooks (钩) to catch fish. Longline fishing is especially common in the Japanese fishing industry. Records showed that Japanese boats used to catch about ten fish for every one hundred hooks. The study says longline fishing boats now might catch one fish per hundred hooks. The scientists say business fishing can destroy groups of fish much faster than in the past. It's not the only worry that the number of large fish is becoming smaller and smaller. What's worse, they are smaller in size than their ancestors (祖先). | ||||||||||||
| 根据短文内容完成表格，每空一词。 What is happening to ocean fish?
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