题目内容
An INTERESTING experiment
It takes a little skill to do this experiment, but the result is truly SURPRISING.
What do you need? Several rubber balloons Wooden skewer（木签） Vegetable oil Paper towel |
| Step l Blow up a balloon, let some of the air out of it, and tie it closed. |
| Step 2 Rub some oil on skewer with paper towel. | |
| Step 3 Gentle twist（搓捻）and push skewer into end of balloon opposite the knot. If balloon pops（爆 炸），go back to Step 1. | |
| Step 4 When skewer is in balloon, slowly twist and push it out of balloon near knot. | |
What will happen? |
| 28 The balloon does not pop, even though it has a skewer in it. |
Why won't it pop? | Rubber is made out of long chains of molecules （分子）. The skewer pushes these molecules aside. The molecules mix with the oil and they stick together tightly. The oil on the skewer seals the hole and air cannot get out. |
1.Which is the most suitable word for 28 ?
A.Topic B.Result C.Problem D.Reason
2.What’s the proper meaning of the underlined word "seals"？
A.密封 B.润滑 C.点燃 D.腐蚀
3.What can we infer（推断）from the passage?
A.It's easy to push a skewer into and out of a balloon.
B.You'd better blow as much air as possible into a balloon.
C.There's no need for you to use the oil while doing the experiment.
D.It's hard for the air to get out of the hole as molecules and oil stick together.
