问题 选择题

下列叙述正确的是          ( )

A.氯化钠晶体不能导电,所以氯化钠不是电解质

B.氯化钠溶液能导电,所以氯化钠溶液是电解质

C.熔融的氯化钠和氯化钠溶液都能产生自由移动的离子

D.氯化钠熔融时不破坏氯化钠晶体中的离子键。

答案

答案:C

溶于水或熔融状态下能电离出阴阳离子的化合物是电解质,氯化钠是电解质,熔融时破坏的是离子键,所以选项C正确,其余都是错误的,答案选C。

填空题
阅读理解

阅读理解。

     A car needs gas to run and your body also needs food to work for you. Eating the right kind

of food is very important. It can help your body grow strong, so take care of what you eat.

    There are four main food groups altogether. The dairy group(乳制品) has food like milk, cheese

and sour milk. The other three groups are the meat and fish group, the fruit and vegetable group,

and the bread and rice group. Each meal should have at least one food from all four main groups.

With all these food together, you will be given enough energy during the day.

    It is easy to get into bad eating habits. You may eat your breakfast in a hurry to get to school on

time. Or you may not have time for a good lunch. It may seem easy to finish your supper with fish

and chips all the time. But you will find yourself tired in these days and you can not think quickly.

    Watching what you eat will help keep your body healthy and strong. It is also good to take some

exercise. It will help you eat more if you take a walk or play games in the open air. Having a good

eating habit with some exercise is the key to your health.

1. Which of the following diets do you think is the best one?

A. Milk, bread, cabbage and beef.      

B. Eggs, tomatoes and chicken.  

C. Corn, fish, cream and pork.         

D. Rice, beancurd, apples, fish and chicken.

2. In the passage the writer mainly tells us that________.

A. every person needs food to grow well

B. taking exercise can keep your body strong

C. right kind of food with exercise will keep you healthy

D. enough energy helps people think more quickly

3. The best title for the passage is_________.

A. The Four Food Groups                  

B. A Healthy Diet 

C. Your Body and Food                    

D. The key to Your Health