扫    sǎo____       sào____

扇    shàn____      shān____

    Tom and Mike had a very good time last Sunday.That morning，they1at six o'clock and dressed(穿衣)themselves.2having breakfast，they went to the park.It's in the centre of the city. In the park.there were a lot of nice flowers.Mike wanted to 3one，but Tom stopped(阻止)him.He told Mike it was not.4to pick flowers.Then they went to the lake.By the lake,they saw a small5.They jumped into it and started a tour on the lake.Two hours6,they left the lake and walked up the hill(小山)near the lake.They got to the top at half past eleven.There they had their lunch.7did they have for lunch?Eggs，bread and oranges.In the afternoon,they 8home.When their mother asked them about the morning，9answered，"It was great.We10ourselves(我们自己)all the morning."

小刚、小毅、小勇、小强在小组合作交流中一起讨论有关巴西的问题，各自的观点不同。你认为谁的说法不正确（    ）

某实验小组对中学课本中可生成氢气的反应进行了研究，总结出三个可以生成H₂的反应：①Zn+盐酸；②Na+水；③Al+NaOH溶液．为点燃上述三个反应生成的H₂，他们设计了如图所示的装置图：

请回答下列问题：

（1）在点燃H₂之前必须先进行 ____．

（2）实验小组在点燃用上述装置制得的H₂时，①③实验获得成功，②却失败了．

他们分析认为失败的原因是Na与H₂O的反应速率太快，Na的用量又太少．于是他们准备增加钠的用量，可老师说太危险，你认为产生危险的原因是 ____

（3）实验小组查阅钠、苯（一种不溶于水的液态有机物）、水的密度分别为0.97g/mL、0.88g/mL、1.00g/mL，并据此对实验进行了改进．

在改进后的实验中H₂的生成速率 ____．（填减慢或加快）

（4）2.3g钠投入20mL水中完全反应所得溶液的物质的量浓度是　 ____．（不计溶液体积的变化）