化学就在我们身边,它能改善我们的生活。请从“ A.氧气 B.氮气 C.生石灰 D.

题型:填空题

问题:

化学就在我们身边,它能改善我们的生活。请从“A.氧气 B.氮气 C.生石灰 D.熟石灰 E.明矾 F.尿素”中选择适当的物质填空(填字母)。

(1) 抢救危重病人常用的物质是            ; (2) 用于农作物肥料的物质是_______;

(3) 常用作袋装食品干燥剂的是______; (4) 净化水时可作絮凝剂的是_______。

考点:化肥水的净化氧气的用途生石灰的性质和用途
题型:填空题

Our factories and homes burn coal and oil. Every year we have forest fires somewhere. Many scientists believe that the climate is changing.

The earth will perhaps be warmer by about 7 degrees centigrade. At the South Pole and the North Pole, the ice will melt (融化). The sea level (海平面) will rise by about 7meters. As a result, water will cover cities like London, Tokyo and New York. Some ports and towns along the coasts will disappear under water.

Some other scientists think that the dust, smoke and pollution from coal, wood and oil fires will block out the sunrays(紫外线). Then the earth will become colder and great sheets of ice will cover Europe and North America.

When chemicals in the air mix with rain, we have acid (酸) rain. Acid rain can bring us great harm. It destroys forests and kills life in lakes and rivers.

People are beginning to see how serious the problem is. They find it important to work with nature instead of against it. They are trying to save the earth in many different ways. But one of the most important things to do is to make people understand that saving the earth is saving ourselves.

小题1:Some scientists believe that          .               

A. the earth is growing warmer

B. we can find oil in our forests

C. we have to burn down the forests every year

小题2:Ice at the poles will          if the earth gets warmer.

A. cover cities like London and Tokyo

B. raise the sea level by 7 degrees

C. become water and make the sea level rise                

小题3:Acid rain          .

A. brings great changes in our climate

B. kills pests in lakes and forests

C. kills the fish in rivers and lakes                        

小题4:What can we learn from the third paragraph?

A. The dust together with pollution from coal, wood and oil fires will bring us more heat from the sun.

B. The sunrays will come more because of the dust and pollution from fires.

C. As a result of the dust and pollution from coal, wood and oil fires, the earth will become colder.                                                                  

小题5:Which statement is TRUE?

A. People have come to know the importance of working with nature.                

B. All the scientists agree that our earth is sure to become warmer and warmer.

C. The sea level will rise if the earth gets colder.

题型:填空题

如图所示的电路中,电源的电动势E=12V,内阻未知,R1=8Ω,R2=1.5Ω,L为规格“3V,3W”的灯泡,开关S断开时,灯泡恰好正常发光.(不考虑温度对灯泡电阻的影响)试求:

(1)灯泡的额定电流和和灯丝电阻;

(2)电源的内阻;

(3)开关S闭合时,灯泡实际消耗的功率.

题型:填空题

拉乌尔定律说明了()中各个组分的分子克服液面阻力进入汽相的趋势.

题型:填空题

为加强北京市的公路建设和管理,促进公路事业发展,根据《中华人民共和国公路法》、《收费公路管理条例》及有关法律、法规,结合北京市实际情况,制定什么条例?()

A、北京市公路条例

B、北京市道路条例

C、北京市道路管理条例

D、以上都有

题型:填空题

运行中断路器有哪些维护要求?

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