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 weigh than fresh water. See for yourself!

You Will Need:

● 3 cups of warm water

● Measuring cup (量杯)

● Wide-mouthed jar

● Salt

● 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(攪拌) 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 liquid will not mix together.

5. Gently place the potato into the jar. Do not 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 halfway down.

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

A．Add the salt to the water.                 B．Stir the salt into the water.

C．Place the potato in the jar.                 D．Pour warm water into thejar.

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

 

【答案】

1.C

2.D

3.B

4.A

【解析】

試題分析：本文介紹了一個(gè)證明鹽水的浮力比淡水的浮力大的實(shí)驗(yàn)。

1.C 細(xì)節(jié)題。根據(jù)You Will Do:中的5 Gently place the potato into the jar. Do not drop it說(shuō)明C正確。

2.D 細(xì)節(jié)題。根據(jù)Add another 1.5 cups of water. Pour it slowly over the back of the spoon into the jar so that the two liquid will not mix together中的so that the two liquid will not mix together指這兩種液體不要混在一起。故D正確。

3.B 細(xì)節(jié)題。根據(jù)You Will Do:中的2 Add 1/3 cup of salt.說(shuō)明B正確。

4.A 推理題。根據(jù)Gently place the potato into the jar. Do not drop it中的Do not drop it不要扔下去，說(shuō)明要輕輕地放，故A正確。

考點(diǎn)：考查科普類(lèi)實(shí)驗(yàn)

點(diǎn)評(píng)：本文考查的細(xì)節(jié)題特多，答題時(shí)在文章找到對(duì)應(yīng)的地方，用筆進(jìn)行標(biāo)記，這有利于后期有時(shí)間檢查時(shí)可以立刻找到答案的位置。仔細(xì)理解作者所講的意思，再結(jié)合選項(xiàng)，通過(guò)排除法和自己對(duì)全文的把握，選出正確答案。

 

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