题干

食盐和味精是厨房里常用的两种调味品,这两种物质都能溶于水。在相同条件下,哪种物质的溶解能力更强呢?小明进行了如下实验探究:

  • 在甲和乙两只相同的烧杯中,分别倒入50克冷水和50克热水,用天平称取食盐和味精各20克,把食盐倒入甲烧杯的冷水中,把味精倒入乙烧杯的热水中;

②用玻璃棒搅拌,使它们充分溶解后,甲烧杯中食盐还有剩余,乙烧杯中味精全部溶解;

③结论:味精在水中的溶解能力比食盐强。

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When settlers (移民)came to America during the 1600s, they were surprised to find so many trees. Some trees were so huge that a large man could not put his arms around them. Those trees helped the settlers a lot. They were glad and thankful to have these trees. They used them to build houses and make fire. From the wood of the trees, they made furniture, tools and so on.

Most people thought the forests would last forever. However, by 1800, America had its first wood shortage (短缺). How did it happen? People had not known that trees were being cut down faster than new ones could grow.

Some American people made trips to foreign countries. There they saw destroyed forests and learnt the importance of protecting forests. They came back to the United States and warned that if Americans didn’t use trees more carefully and wisely, someday the forests would all be gone. However, people were not ready to listen. Years went by, and America’s forests kept disappearing. It made some people really worried. But they did nothing.

Finally, J. Sterling Morton, the man who is remembered as the father of Arbor Day (过节), got people to listen. He named a Tree-Planting Day, or Arbor Day. He worked hard to make Arbor Day a national holiday. On that day, people usually plant a lot of trees.

Today, millions of trees have been planted in the United States because of Arbor Day. Arbor Day is such a good idea that many other countries now also have Arbor Day. Many, many trees are being planted all over the world because of J. Sterling Morton’s work.