Youknowthatballoonsmustbekeptawayfromsharpobjects.Theya...

问题详情：

You know that balloons must be kept away from sharp objects. They also needed to be kept away from flames. A fire can weaken the rubber and cause it to break. However, in this experiment you will find out how you can hold a balloon directly in a flame without breaking the balloon.

   Materials needed:

●         two round balloons not inflated(充气的)

●         several matches

●         water

Inflate one of the balloons and tie it. Place 1/4 cup of water in the other balloon, and then inflate it

and tie it. Light a match and hold it under the first balloon. Allow the flame to touch the balloon. What happens? The balloon breaks, perhaps even before the flame touches it. Light another match. Hold it directly under the water in the second balloon. Allow the flame to touch the balloon. What happens to this balloon? It doesn’t break.

   Why does the balloon with no water break in the flame? The flame heats the rubber of both balloons. The rubber of the balloon without water becomes so hot that it becomes too weak to resist the pressure of the air inside the balloon. However, when the balloon with water in it is placed in the flame, the water takes in most of the heat from the flame. Then, the rubber of the balloon doesn’t become very hot, it doesn’t weaken, and the balloon doesn’t break.

   Water is a particularly good absorber(吸收者) of heat. It takes a lot of heat to change the temperature of water. On the other hand, when water cools, it gives off a great deal of heat. That’s why areas near oceans or other large bodies of water don’t get as cold in winter as areas at the same latitude(纬度) further inland.

28. From the passage we can know the following aspects of the experiment except______.

A. method             B. material             C. result            D. time

29. What does the underlined word “resist” in Para 4 probably mean?

A. add                B. expand              C. bear             D. form

30. When the flame reaches the balloon with water inside, ______

A. the rubber of it doesn’t become hot at all

B. the water in it begins to boil

C. the balloon breaks

D. the heat is mostly taken in by the water            

31. The purpose of the experiment described in the passage is to prove that______.

A. water is a particularly good absorber of heat

B. some balloons can be easily broken, while others can’t.

C. balloons without water are not as strong as those with water inside.

D. the temperature is not up to the latitude.

【回答】

DCDA

知识点：阅读理解

题型：阅读理解