问题 填空题

制冷剂是一种易被压缩、液化的气体,液化后在管内循环,蒸发时吸收热量,使环境温度降低,达到制冷目的。人们曾采用过乙醚、CH3Cl等作为制冷剂,但它们不是有毒,就是易燃。于是科学家根据元素性质的递变规律来开发新的制冷剂。据现有知识,某些元素化合物的易燃性、毒性变化趋势如下:  

(1)氢化物的易燃性:第二周期:__>____> H2O>HF;第三周期:SiH4>PH3>____>____  

(2)化合物的毒性:PH3> NH3;H2S____H2O;CS2_______CO2;CCl4> CF4。(填“>”或“<”)  

(3)科学家们开始把注意力集中在含F、Cl的化合物上。已知CCl4的沸点为76. 8℃,CF4的沸点为-128℃。新制冷剂的沸点范嗣介于其间。经过较长时间的反复实验,一种新的制冷剂氟利昂(CF2Cl2)终于诞生了。然而,这种制冷剂造成了当今的某一环境问题,它是______,但这种求助于周期表中元素及其化合物的___(填序号)变化趋势来开发制冷剂的科学思维方法是值得借鉴的。

  ①毒性②沸点③易燃性④水溶性⑤颜色

答案

(1)CH4;NH3;H2S;HCl

(2)>;>

(3)破坏了臭氧层;①②③

阅读理解

阅读理解

     China_is_going_green. In order to reduce air pollution and oilshortages, automobile manufacturers

have announced their plans to develop hybrid vehicles (混合燃料汽车) for the Chinese market.

Toyota's hybrid car Prius will be ready to drive in China this week. Let's have a look at the new car.

     Any vehicle is a hybrid when it combines two or more sources of power. Hybrid cars run off a

rechargeable battery and gasoline. Hybrid cars have special engines, which are smaller than traditional

gasoline engines. They run at 99 percent of their power when the car is cruising (匀速行驶). A specially

designed battery motor provides extra power for running up hills or when extra acceleration is needed.

     Step into a Prius, and turn on the engine. The first thing you notice is how much quieter it is than a

traditional car. At this point, the car's gasoline engine is dormant (休眠). The electric motor will provide

power until the car reaches about 24 km/h. If you stay at a low speed, you are effectively driving an

electric car, with no gasoline being used, and no waste gas gives off.

     The onboard(车载的) computer makes the decision about when to use a gas engine, when to go

electric, and when to use a combination of the two. If you go over 24 km/h, when you step on the gas

pedal (油门), you are actually telling the computer how fast you want to go.

     The electronic motor recharges automatically using a set of batteries. When driving at high speed, the

gasoline engine not only powers the car, but also charges the batteries. Any time you use the brake, the

electric motor in the wheels will work like a generator and produce electricity to recharge the batteries.

As a consequence, the car's batteries will last for around 200,000 miles.

1. The author writes this passage mainly to________.

A. teach people how to drive a hybrid car

B. introduce a new kind of "green" car

C. show how to save their gasoline when driving a car

D. announce plans to develop hybrid vehicles for China

2. The first sentence probably refers to ________.

A. there will be more and more green land in China

B. China is still young and lacking experience

C.China's new cars are combinations of different green models

D. China has started producing environmentally friendly cars

3. Which of the followings is NOT true?

A. The hybrid cars reduce air pollution and oilshortages.

B. The car's gasoline engine doesn't work until it reaches about 24 km/h.

C. This kind of car is completely controlled by an onboard computer.

D. A specially designed battery motor provides extra power when needed.

4. What is the most important feature of hybrid cars?

A. They are powered by both a rechargeable battery and gasoline.

B. They are much quieter than traditional cars.

C. They only use 99 percent of their power to run up hills.

D. They have smaller engines than traditional gasoline ones.

5. What can we conclude from the story?

A. The batteries can be recharged at any time you want.

B. Using the brake suggests that the gasoline engine should work.

C. The batteries will last for 200, 000 miles without being recharged.

D. The gasoline engine charges the batteries as well as powers the car.

单项选择题