问题 填空题

完成下列化学方程式:

(1)木炭的燃烧______;

(2)淡黄色固体在氧气中燃烧______;

(3)镁与氧气反应的化学方程式______;

(4)氯酸钾与二氧化锰混合共热生成氯化钾和氧气______;

(5)用木炭还原氧化铜的化学方程式______;

(6)乙醇在空气中燃烧的化学方程式______.

答案

(1)碳在氧气充足的条件下生成二氧化碳,在氧气不充足的情况下生成一氧化碳,故答案为:C+O2

 点燃 
.
 
CO2或2C+O2
 点燃 
.
 
2CO

(2)硫和氧气在点燃的条件下生成二氧化硫,故答案为:S+O2

 点燃 
.
 
SO2

(3)镁和氧气在点燃的条件下生成氧化镁,故答案为:2Mg+O2

 点燃 
.
 
2MgO

(4)氯酸钾在二氧化锰作催化剂加热的条件下生成氯化钾和氧气,故答案为:2KClO3

MnO2
.
2KCl+3O2

(5)碳和氧化铜在高温的条件下生成铜和二氧化碳,故答案为:C+2CuO

 高温 
.
 
2Cu+CO2

(6)乙醇和氧气在点燃的条件下生成二氧化碳和水,故答案为:C2H5OH+3O2

 点燃 
.
 
2CO2+3H2O

阅读理解

阅读理解。

    Plants and animals, including humans, need food and water to live on. These are from the natural resources

(资源) on Earth. To protect these resources, we need to keep the air clean and the water drinkable. We need

to keep the soil healthy. How do we do that?

* Protect the land

    The soil that covers fields and farms provides much of the food we eat. Human activities such as plowing (耕) fields, mining (采矿), and building highways can destroy (破坏) the land. Erosion happen when wind and

water carry away the soil. Soil erosion can turn rich farmland into a desert wasteland. So does this mean we

shouldn't build a highway or plow a field? Of course not. But it does mean we might think about Earth-friendly

ways of doing those things.

    Today farmers plow their fields in different ways to prevent erosion. They try to use less water for their

crops. They keep animals from eating the growing grass in just one area. Farmers also plant trees to prevent

erosion from happening.

* Save the Trees

    Another human activity that damages the land is deforestation (采伐森林). People take away a large number

of trees from a forest. Millions of square kilometers of forest disappear each year. When this happens, many

plants and animals lose their places to live. They may die out, or become very few. Scientists haven't even

discovered all the living things in the forest. We may be losing some without even knowing they are there.

Trees absorb (吸收) and use carbon dioxide (二氧化碳) when they make food. Environmentalists encourage

careful management of the forests. They ask people to replant trees after they cut down the forest. 

* Recycle, Reuse, Reduce

     People throw a piece of paper into the wastebasket after using it. The paper becomes trash. Where does

the trash go next? Much of our trash ends up in landfills (垃圾填埋地). They take up valuable land and

sometimes pollute the water, air, and land around them. More than a third of the trash in landfills is paper.

Recycling, reusing, and reducing what you throw away can cut down on the need for more landfills. In fact,

we can recycle about eighty percent of household trash.

1. What does the underlined word "erosion" mean? [ ]

A. Plowing fields and mining.

B. Cutting down trees and farming.

C. Wind and rain carrying away soil.

D. Building highways on the farmland.

2. How do farmers prevent erosion now? [ ]

A. They try to use more water for their crops.

B. They stop animals from eating the growing grass in just one area.

C. Farmers also plant flowers to prevent erosion from happening.

D. They move to another place.

3. Why do we need to save the trees? [ ]

A. To discover more new trees every year.

B. To make more money.

C. To take away a large number of trees from the forest.

D. To keep good places for animals and plants to live in.

4. How much of the trash can we recycle? [ ]

A. All the trash.

B. Very little.

C. One third.

D. Four fifths.

5. What's the purpose of the author writing the passage? [ ]

A. To ask people to look for places to plant trees.

B. To tell people how to protect natural resources.

C. To show how the lands are destroyed by people.

D. To discuss ways of protecting animals and plants.

论述题