Put an ice cube from your fridge into a glass of water. You have a piece of string(线) 10 centimeters long. The problem is to take out that piece of ice with the help of the string. But you must not touch the ice with your fingers.
You may ask your friends to try to do that when you are having dinner together. There is a saltcellar on the table. You must use salt when you carry out this experiment.
First you put the string across the piece of ice. Then put some salt on the ice. Salt makes ice melt(融化). The ice round the string will begin to melt. But when it melts, it will lose heat. The cold ice cube will make the salt water freeze(结冰) again.
After a minute or two you may raise the piece of string and with it you will raise your piece of ice!
This experiment can be very useful to you. If, for example, there is ice near the door of your house, you must use very much salt to melt all the ice. If you don’t put enough salt, the water will freeze again.
【小题1】We must use           when we carry out this experiment.

There is _________"o" and _________ "1" in the word "bowl".

       A. a; a              B. a; an             C. an; a           D. an; an

There is _________"o" and _________ "1" in the word "bowl".

Have you ever seen the film Titanic? “Titanic” was one of the largest and finest ships in 1912. It hit an iceberg(冰山)on its first sailing from England to America and sank very soon, leaving a love story to the people. Do you know what an iceberg is?
The earth is round, like a ball. The top of the earth is the north. The bottom of the earth is the south. At the top and the bottom of the earth, there is a lot of ice. It is very cold there. Sometimes there is no sunshine for many months. There is ice everywhere all the time. Large pieces of ice fall into the sea. They don’t go to the bottom of the sea. They float(漂浮)near the top of the water. We call these large pieces of ice “iceberg”. Some icebergs are bigger than a tall building. Icebergs are dangerous for ships. Sometimes a ship hits an iceberg.
Then the ship sinks.
You can make a small iceberg. Put a piece of ice in a glass of water. Look ar it. The ice does not sink.
【小题1】Titanic is the name of a film and it’s also the name of a _______.
【小题2】Titanic sank ________ it hit an iceberg.
【小题3】The __________ is very cold in North Pole(北极)and in South Pole.
【小题4】At times we can’t see the ___ in North Pole and in South Pole for a long time.
【小题5】 Icebergs are made of large _________.