问题 填空题

取一支蜡烛,用小刀切下一块,这说明蜡烛的硬度______,将其放入水中,蜡烛浮在水面上,这说明蜡烛的密度比水______,将蜡烛点燃,观察到蜡烛的火焰分______、______、______三层.把火柴梗放在火焰上1秒后取出,可以看到火柴梗______的部分最先碳化,这说明蜡烛火焰的______温度最高.将一只干燥的烧杯罩在蜡烛火焰的上方,烧杯内壁出现了______,片刻后取下烧杯,迅速向烧杯内倒入少量澄清的石灰水,振荡,澄清的石灰水变______,这说明蜡烛燃烧后生成了______和______.

答案

蜡烛能用小刀切下一小块,说明质软,硬度小,把它放入水中,蜡烛浮在水面上,说明蜡烛的密度比水小,且难溶于水;

蜡烛燃烧火焰分为三层:外焰、内焰、焰心,把火柴梗放在火焰上1秒后取出,外焰部分最先碳化,由此说明蜡烛火焰外焰温度最高;

由于蜡烛燃烧产物是二氧化碳与水,所以在烧杯内会有水雾出现,由于生成二氧化碳,所以能使澄清石灰水变浑浊;

故答案为:

小;     小;   焰心、内焰、外焰;     外焰;     外焰;

水雾;  浑浊;  水、二氧化碳.

阅读理解

阅读理解。

     There is an old saying (谚语): Early to bed, early to rise, makes a man healthy, wealthy and wise (富有

而有智慧). It means that we should go to bed early and get up early the next morning. By doing this, we will

be in good health. And we'll also be rich and clever.

     It's true that our bodies need to have enough sleep to be healthy. Children should have a ten-hour sleep

every night. Those who do not have enough sleep can't do their work very well. They will not be clever and

they may not get wealthy in the future.

     The body needs exercise too. Walking, running, jumping, riding bikes and playing games are all exercise.

Exercise helps to keep the body strong and fit. It also helps the blood (血液) to move around inside the body.

The head needs blood too. So exercise helps people think better.

1. What does the underlined word "rise" mean?

A. To do exercise.

B. To get up.

C. To stand up.

D. To put up.

2. If children don't sleep for 10 hours every night, they may _______.

A. not be late for school

B. become wise

C. do badly in their work

D. become rich

3. A person needs exercise because _______.

A. it makes him healthy

B. he has lots of work to do

C. he is strong

D. he does exercise

4. Which of the following is NOT true?

A. Exercise is good for people.

B. It's good for you to get up early and go to bed early.

C. If you have enough blood, you will be wise.

D. A student should have 10 hours' sleep every night.

5. What's the meaning of "Early to bed, early to rise"?

A. The sun rises in the morning and sets (落下) in the evening.

B. You should get up early and go to bed late.

C. The sun rises early and sets late.

D. You should get up early and go to bed early.

单项选择题