Question

  It is easier to float in the ocean than it is to float in a swimming pool. Do you know why?

  Ocean water is full of salt,and salt water can hold up more weight than fresh water. See for yourself!You will need：

. 3 cups of warm water

. Measuring cup (跫杯)

. Wide-mouthed jar

. Sail

. Spoon

-Raw (生的) potato 

You will do:

1. Pour 1. 5 cups of warm water into the jar.

2. Add 1/3 cup of salt.

3. Stir (搅拌) until the salt is completely dissolved.

4. Add another 1. 5 cups of water. Pour it slowly over the back of the spoon into the jar so that the two liquids will not mix together. 

5. Gently place the potato into the jar. Donot drop it. What will happen： The potato will sink,but only halfway!

Why： 

  Salt water is heavier than fresh water,so it will stay on the bottom. The fresh water will remain on top.

  The potato is heavier than the fresh water,but it is lighter than the salt water. That is why the potato will sink only halfway down.

1. In the experiment,what should you do right after you pour the water over the spoon?

   A. Add ihe salt to the water.

   B. Stir the salt into the water.

   C. Place the potato in the jar.

   D. Pour warm water into the jar.

2. In Step 4 of the experiment,why do you pour the water over the spoon slowly?

   A. It is easier to see what you are doing.

   B. It pushes the fresh water to the bottom.

   C. It will keep the water from coming out.

   D. It will keep the liquids from mixing together.

3. In which step of the experiment do you add the salt?

   A. Step 1.  B. Step 2. C. Step 3.  D. Step 4.

4. What does the underlined word Gently" mean?

   A. Carefully.

   B. Quickly.

   C. Secretly.

   D. Silently.

5. What is the most important detail about salt water in this text?

   A. You can make it yourself.

   B. You can find it in the ocean.

   C. It is heavier than fresh water.

   D. A potato will sink in it.

Answer 1

本文讲了一个小实验：如何能够让土豆在盐水中漂浮。

1. C细节理解题。第四步提到了将水顺着勺子背面倒入罐子中，接着应是第五步的操作，即把土豆放人罐子中。

2. D细节理解题。由实验第四步"…so that the two liquids will not mix together."可知，慢慢地把水倒人罐中是为了防止两种液体混合在一起。

3. B细节理解题。"Add 1/3 cup of salt."是第二步。故答案为B项。

4. A词义猜测题。由"Do not drop it."可推知，要小心地放土豆，才能保证土豆掉不下来。carefully与gently意思相近。

5. C推理判断题。该实验通过土豆可以漂浮在盐水中说明，盐水的浓度比淡水的浓度大。