A
An egg sinks to the bottom if you drop it into a glass of ordinary drinking water but what happens if you add salt? The results are very interesting and can teach you some fun facts about density(密度)．
What you'll need：
* One egg * Water * Salt * A tall drinking glass
Instructions：
Pour water into the glass until it is about half full.
Mix in lots of salt(about 6 tablespoons)．
Carefully pour in plain water until the glass is nearly full (be careful not to mix the salt water with the plain water)．
Gently lower the egg into the water and watch what happens.
What's happening?
Salt water is denser than ordinary tap water. The denser the liquid is, the easier it is for an object to float in it. When you lower the egg into the liquid it drops through the normal tap water until it reaches the salt water, and at this point the water is dense enough for the egg to float. If you were careful when you added the tap water to the salt water, they would not mix, enabling the egg to amazingly float in the middle of the glass.
21. Which of the following is the CORRECT order？________
①Mix in lots of salt.
②Gently lower the egg into the water.
③Carefully pour in plain water until the glass is nearly full
④Pour water into the glass until it is about half full.
A. ④②①③ B. ④①③②
C. ①④③② D. ③④①②
22. Why can the egg float in the water according to the passage？________
A. Because ordinary tap water is denser than salt water.
B. Because ordinary tap water is as dense as salt water.
C. Because the denser the liquid is, the easier it is for an object to float in it.
D. Because the more the liquid there is, the easier it is for an object to float in it.
23. What will happen if you drop an egg into a glass of water with about 6 tablespoons of salt？ ________
A. It will float in the water.
B. It will sink to the bottom.
C. Nothing will happen.
D. The result is not known.
【答案】21. B 22. C 23. A
【解析】
【分析】本文是一篇說明文，是一個關(guān)于密度的雞蛋實驗。
【21題詳解】
細節(jié)理解題。根據(jù)Instructions部分的“Pour water into the glass until it is about half full.Mix in lots of salt(about 6 tablespoons)．Carefully pour in plain water until the glass is nearly full (be careful not to mix the salt water with the plain water)．Gently lower the egg into the water and watch what happens.（將水倒進玻璃杯直到半滿。加入大量的鹽(大約6湯匙)。小心地倒入白水，直到杯子幾乎滿了(注意不要把鹽水和白水混合)。輕輕地把雞蛋放入水中，看看會發(fā)生什么。）”可知，正確的排序是④①③②，故選B。
【22題詳解】
推理判斷題。根據(jù)What's happening?部分的“Salt water is denser than ordinary tap water. The denser the liquid is, the easier it is for an object to float in it.（鹽水比普通自來水的密度大。液體密度越大，物體就越容易漂浮在其中。）”可知，雞蛋之所以能浮在水里是因為液體的密度越大，物體就越容易漂浮在其中。故選C。
【23題詳解】
細節(jié)理解題。根據(jù)Instructions部分的“Mix in lots of salt(about 6 tablespoons)（加入大量的鹽(大約6湯匙)）”和最后一段的“When you lower the egg into the liquid it drops through the normal tap water until it reaches the salt water, and at this point the water is dense enough for the egg to float.（當你把雞蛋放入液體中時，它會在普通的自來水中下降，直到它到達鹽水，此時水的密度足夠讓雞蛋漂浮起來。）”可知，如果你把一個雞蛋扔進一杯加了6湯匙鹽的水中，它就會浮在水中，故選A。
