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1、Listening and Writing (Students Book: p. 46)mr. chen:OK, boys and girls, were going to do an experiment. Come a bit closer. The closer you are, the more youll see! Thats right! Now, whats the aim of this experiment, Zhou Kai?zhoukai:We want to find out if theres a change in weight when magnesium bur
2、ns in air.mr. chen:Thats right. So what do we need first?zhou kai:Um . We need some magnesium. How much do we need? What about this piece? Is this piece OK?mr. chen:No, we need rather more than thatabout two and a half grams. We need a piece which is much bigger than that.zhou kai:OK . And we need a
3、 Bunsen burner . a balance . and a crucible to put the metal in . Here they all are . Where do we go from here?mr. chen:Well, first, put the magnesium in the crucible. Then put the crucible on the balance and weigh it.zhou kai:OK.mr. chen:How much does it weigh? Take a look, everyone. Is it any heav
4、ier?zhou kai:Um . It weighs two and a half grams. Do you want me to write that down?mr. chen:Yes, write it down. What next?zhou kai:Yes . Um, next, were going to heat the magnesium. So I light the Bunsen burner. After that, I hold the crucible over it . Oh look, its burning with a white light! Its g
5、etting brighter and brighter!mr. chen:Its pretty, isnt it? Keep the noise down, boys and girls, please.zhou kai:Um . lastly, we need to weigh the magnesium again . It weighs four grams now.mr. chen:So what does that tell you?zhou kai:It weighs a little more than before.mr. chen:How much more?zhou ka
6、i:1.5 grams more.mr. chen:And what does that mean?zhou kai:It means that there is a change in weight when magnesium burns in air.mr. chen:Youve got it! Well done! So now, lets do the same experiment with copper. Come along, Li Kang, its your turn now. What do you think will happen if you heat copper?li kang:I think itll be a lot heavier than magnesium. Shall I begin?mr. chen:Yes, go ahead!