问题 填空题

汽车发动机工作时把内能转化为______能,当汽油在发动机内燃烧不充分时会冒“黑烟”,这时发动机的效率______(选填“升高”、“不变”、“降低”).发动机散热器常用水做冷却剂,这是因为水的______大.

答案

汽车发动机工作时将内能转化为机械能;

冒“黑烟”说明燃烧不充分,用来做有用功的能量占燃料完全燃烧放出的总能量的比值就小,所以效率降低;

用水做冷却剂是因为水的比热容较大,在相同条件下能吸收更多的热量.

故答案为:机械,降低,比热容.

阅读理解

According to a new survey, student safety has become a big problem. Nearly 50% of students say they are worried about robbery(抢劫) on the way to and from school. Now in many big cities in China, some schools have taught an unusual lesson: self-protection(自我保护). Students like this lesson because there are no exams or boring classes. And they can learn how to save lives and know how to stop danger before it really happens.

Chen Haoyu, a teacher at Beijing No.25 Middle School and a self-protection expert(专家), gives young students advice on how to deal with danger.

If you are robbed

Keep calm. If you can not cry for help or run away, give the robber your money. Try to 

remember what the robber looks like and tell the police later.

If you are in a traffic accident   

If a car hurts you, you should remember the car number; if it is a bicycle, try to call your

parents before you let the rider go. This is because you don’t know how badly you are hurt.

If it is raining hard and there is lightning(闪电)

Don’t stay in high places and keep away from trees.

When there is a fire

Get away as fast as you can. Put wet things on your body and try to find an exit (出口).

Do not take the lift!    

If someone is drowning (溺水)

If you can’t swim, don’t get into the water. Cry out for help. Remember that danger is never as far away as you think. Take care of yourself at all times!

小题1:Why do students like the self-protection lesson?

①Because there are no tests.

②Because the lesson is boring.

③Because they can learn how to save lives.

④Because they know how to stop danger before it happens.

A.①②

B.②③

C.①②④

D.①③④小题2:If your house is on fire, you must _______.

A.putdrythingsonyourbody

B.runquicklyandtakethelift

C.runawayandfindanexitasquicklyasyoucan

D.takeeverythingyouhaveandthenrunaway小题3:The best title for the passage is         .

A.How to Keep Calm

B.Self-protection

C.An Unusual Lesson

D.Danger

选择题