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2. Know the usage of the key words and expressions.?
Teaching methods: Listening,Reading,Groupwork.
Preparation before class: a candle,a candle holder,a big glass jar,a shallow dish,some water,a lighter or matches.
教学过程：
Ⅰ.目标导入
Think about the questions:
1.Do you like doing science experiments? Why or why not?
2.What will happen if you put a jar upside down over a burning candle?
Ⅱ.预习检测
Read the lesson and fill in the blanks.
Let’s do the experiment together! Put the candle in the candle holder. Put the candle holder on the dish. Fill the dish half full with water. Light the candle with a ______ or a lighter. What can you see? The candle is burning. _____ the candle burn for two or three minutes. Then carefully put the jar over it until the top of the jar rests on the dish. As the candle burns, it_____ the oxygen in the air. When the candle stops _________, it has uses up all the oxygen in the air. The water inside the jar_____ and fills about________ of the jar. This is because about one fifth of the air is made up of oxygen.
Ⅲ.质疑互动
1.Listen to the tape and read the text together.
2.Do the experiment in groups.
3.Discuss and find out the key phrases.
①When the candle stops burning, it has used up all the oxygen in the air.
当蜡烛停止燃烧时，它已经耗光了空气中的氧气。
use up 用尽；耗光
例如：他已用完了所有的纸。
He has used up all the paper.
②Because about one fifth of the air is made up of oxygen, the water rises and fills about one fifth of the jar.
因为空气的五分之一是由氧气组成的，所以水会上升到瓶子五分之一的位置。
be made up of “用……构成或组成的”，指结构成分，指人、物皆可。
例如：这个句子是由五个单词组成的。
This sentence is made up of five words.
Ⅳ.达标纠错
一、根据汉语提示完成句子。
1. She?rubbed?another?______ (火柴)?on?the wall.
2. The dish is too _______ (浅的) to serve soup in.
3. We?should?________ (检查) ourselves?and learn who?we?are.