Question

9．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 arc 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，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 will not have mixed，enabling the egg to amazingly float in the middle of the glass．
 
21．Which of the following is the CORRECT order？B
①M(fèi)ix 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．④②①③B．④①③②C．①④③②D．③④①②
22．What will happen if you drop an egg into a glass of water with about 6 tablespoons of salt？A
A．It will float in the water．
C．Nothing will happen．
B．It will sink to the bottom．
D．The result is not known．
23．Why can the egg float in the water according to the passage？C
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．

Answer 1

分析 短文主要介紹了一個實(shí)驗(yàn)，把蛋放在鹽水里面，最后蛋漂浮起來的過程．

解答 21．B．細(xì)節(jié)理解題．根據(jù)文章中的"Instructions"部分可知，先倒一半的水，再加鹽，再慢慢加入淡水直到滿了，最后蛋就慢慢往下了，故答案為B．
22．A．細(xì)節(jié)理解題．根據(jù)文章最后一段的"…at this point the water is dense enough for the egg to float．"可知加入鹽的水密度比較大，可以導(dǎo)致蛋漂浮起來，故答案為A．
23．C．細(xì)節(jié)理解題．根據(jù)文章最后一段"…the denser the liquid is，the easier it is for an object to float in it．"可知液體的密度比較大，物體就更容易漂浮起來，故答案為C．

點(diǎn)評 考查學(xué)生的細(xì)節(jié)理解和推理判斷能力．做細(xì)節(jié)理解題時一定要找到文章中的原句，和題干進(jìn)行比較，再做出正確選擇．在做推理判斷題時不要以個人的主觀想象代替文章的事實(shí)，要根據(jù)文章事實(shí)進(jìn)行合乎邏輯的推理判斷．