问题 填空题

在分子、原子、离子、质子、中子、电子、原子核这些粒子中:

(1)能直接构成物质的粒子是______;

(2)显电中性的粒子有______;

(3)带正电的粒子有______;

(4)带负电的粒子有______;

(5)质量最小的粒子是______;

(6)参加化学反应时,一定发生变化的粒子有______;

(7)在同一原子里数目相等的是______;

(8)决定原子质量大小的粒子主要是______.

答案

(1)水、氧气、二氧化碳等物质是由分子构成,铁、锌、硫、镁等物质是由原子构成,氯化钠等是由离子构成;

(2)中子不带电所以显电中性,因为原子是由带正电的原子核和核外带负电的电子构成,原子核所带电量和核外电子所带电量相等,电性相反,所以整个原子不显电性,又因为分子是由原子构成的,所以分子也不显电性;

(3)一个质子带一个单位正电荷,原子核由质子和中子构成,中子不带电,所以原子核带正电;

(4)一个电子带一个单位的负电荷;

(5)一个质子质量约等于一个中子质量都约等于一个电子质量的1836倍,所以质量最小的是电子;

(6)化学变化的实质是有新物质生成,有新物质生成也就有新分子生成,即分子一定变;

(7)在原子里:质子数=电子数=核电荷数;

(8)一个原子的质量主要集中在原子核上,原子核是由质子和中子构成,所以决定原子质量大小的粒子主要是质子和中子.

故答案为:(1)分子、原子、离子;

(2)分子、原子、中子;

(3)质子、原子核;

(4)电子;

(5)电子;

(6)分子;

(7)质子和电子;

(8)质子和中子.

阅读理解

阅读理解。

     Cats are the most popular pets among Americans. So it is not surprising there are many expressions

about cats. Do you know any of them? Now let me introduce some to you.

     Some cats like to catch small birds, like canaries. If someone looks very proud or satisfied with himself,

we say he looks like the cat that ate the canary.

     Sometimes, a cat likes to play with a small animal it catches. So if you play cat and mouse with someone,

you change between different kinds of behavior when dealing with another person. For example, a child might

offer something sweet to her little brother, and then take it away when reaches for it.

     A cat will often catch a small animal and present it to its owner. The saying that looks like something the

cat dragged in describes something in bad condition.

     A fat cat is a person with a lot of money.

     There are many other expressions about cats in America. How interesting! Which kind of cat are you, or

which kind would you like to be?

1. Americans like ________ best as pets.

A. dogs

B. pigs

C. cats

D. mice

2. The canary is a kind of ________.

A. dog

B. cat

C. bird

D. fish

3. If you have much money, we can call you ________.

A. a fat cat

B. a happy cat

C. a thin cat

D. a sad cat

4. If someone always thinks highly of himself, we can say ________.

A. he plays cat and mouse with someone

B. he looks like the cat that ate the canary

C. he is a lazy cat

D. he has dragged in something

5. The passage introduces us ________ expressions about cat.

A. one

B. two

C. three

D. four

单项选择题