The surprisingexperiment I am about to describeprovesthat air is all around you and that it pressesdownupon you. Air pressure is a powerfulforce. When you swimunderwater, you can feelwaterpushingdown on yourbody. The air all around you does the same. However, yourbody is so used to it that you do not noticethis. The pressure is caused by a layer of air called the atmosphere. Thislayersurrounds the Earth, extending to aboutfivekilometersabove the Earth’s surface.
The followingexperiment is an easy one that you can do at home. But makesurethat you are supervised, because you willneed to use matches. Now for the experiment！
What you need
•A hard-boiled egg without the shell
•A bottlewith a neckslightlysmallerthan the egg
•A piece of paper
1） Checkthat the egg will sit firmly on the neck of the bottle.
2） Tear the paperintostrips and put the stripsinto the bottle.
3） Light the paper by dropping a burningmatchinto the bottle.
4） Quickly sit the egg on the neck of the bottle.
ResultAstonishingly, the egg will be suckedinto the bottle. Yourfriendswill be amazedwhen you showthem the experiment. But be carefulwhen you handlematches.
Why it happened
As the paperburns, it needsoxygen and uses up the oxygen （air） in the bottle. The egg acts as a seal in the neck of the bottle, so no more air can get inside. Thisreduces the air pressureinside the bottle. The air pressuremustequalize, so more air fromoutsidemustenter the bottle. The outside air pressureagainst the egg and then the egg is pushedinto the bottle! Thisprovesthat air is all around and that it is pressingdown on it.
【題組】61. In the experiment, the burninginside the bottle can___.
(A) equalize the air pressureinside and outside (B) make a seal in the neck of the bottle (C) finish up the oxygeninside the bottle (D) producemoreoxygeninside the bottle