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a candle
2. a candle holder
3. a lighter or matches
4.a big glass jar
a shallow dish
6. Some water
What do we need?
What shall we do?
⒈Put the candle in the candle holder.
⒉Put the candle holder on the dish .
⒊Fill the dish half full with water.
⒋Light the candle .
5.Let the candle burn for two or three minutes.
⒍Carefully put the jar upside down
over the candle.
⒎Examine the water in the jar.What can you see ?
What is happening?
1.Why did the candle stop burning?
⒉How far did the water rise ?
when the candle stops burning , it has used up all the oxygen in the air.当蜡烛熄灭时，它就已经消耗完了空气中所有的氧气。
Because about one fifth of the air is made up of oxygen, so the water rises and fills about one-fifth of the jar. 由于大约空气的五分之一是由氧气组成的。
one-fifth
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