问题 问答题

在许多情况下,人们希望能够较快地溶解某些固体物质.某课外小组需一定浓度的硝酸钾溶液做实验.怎样使硝酸钾固体较快地溶于水中?请提出你的操作建议.(写出三条)

答案

搅拌、升温都能加快水分子运动速度,也就能加快硝酸钾与水的接触机会,从而加快了硝酸钾的溶解速率,固体颗粒大小决定了固体与水的接触面积的大小,也能改变溶解速率;溶解前先将硝酸钾固体研碎,即增加了硝酸钾与水的接触面积,也加快了硝酸钾的溶解速度;

故答案为:

(1)溶解前先将固体研碎;

(2)溶解时要加热;

(3)溶解时不断搅拌.

(每条1分)(其他合理答案均可)

完形填空

Children all over the world like to celebrate their birthdays. American children are of no difference. They usually celebrate with a party. They invite their friends to their birthday parties. The party may not be held on the right date of their birthday if it comes on a school day. It may be held on the weekend instead.

Today two kinds of parties are the most popular. One is held at home. Parents decorate the house beautiful with balloons and coloured paper. They prepare a special birthday meal. The children play games. The other kind is held away from home. Some are at a special restaurant. The children eat pizza and ice cream. The waiters , who serve the food, also sing and tell jokes to the children. Other parties may be held at a park, or at a movie theatre, or in some other places.

Every birthday party has a cake with candles on it. There is one candle for each year of a birthday boy’s or girl’s age. When the candles are lighted(点燃), everyone sings the special birthday song: HAPPY BIRTHDAY TO YOU.

As Americans grow older, their birthday parties change. In fact, many people stop having them. They say they would like to forget how old they are. Yet they do like to keep the happy birthday parties of their childhood in mind.

小题1:Who would like to celebrate their birthdays?

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小题2:How do American children celebrate their birthdays?

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小题3:How many kinds of parties are the most popular today?

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小题4:What’s for every birthday party?

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小题5:Why do many of Americans stop having their birthday parties?

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