Carry out an experiment by following the steps below.
1.Fill a beaker with about 200cm3 water.
2.Fix a short candle on a small piece of foam with some plasticine.Then,put the whole thing,with the candle-slide up,into the beaker of water.
3.Light the candle.Cover the burning cadle with a boiling tube as shown below and observe.
Questions
1.(a) What happens to the burning candle after a short while?
(b)Explain your observation in (a)。
2.(a)What happens to the water level inside the boiling tube?
The water level __________(rises/falls) approximately ______________ (one-third/one-fourth/one-fifth) the length of the boiling tube.
(b)Explain why the water level rises/falls.
(c)What does your observation show adout the normal percentage of the related component gas in air?
勁人help 做 F.2 IS
2010-09-22 2:26 am
回答 (3)
2010-09-22 3:23 am
✔ 最佳答案
上面兩位有冇搞錯?!?! 空氣中氧氣 oxygen 得21% (1/5, 五份之一), water level will only rise to one-fifth of boiling tube!
1a. the flame goes out.
1b. combustion of candle wax requires oxygen. when all of the oxygen in boiling tube is used up, the flame cannot sustain and it goes out.
2a. rise, one-fifth.
2b. in combustion of candle wax, all of oxygen is consumed and equal volume of carbon dioxide is released.
however, carbon dioxide can dissolve in water. the total volume of gas inside boiling tube decreases, so the water level rise.
2c. air contains one-fifth, i.e. ~20% of oxygen.
上面兩位未讀好書就咪玩電腦啦, 教錯人累死人呀!!
2010-09-21 21:37:17 補充：
有一位刪除內容了.
2010-09-22 02:02:32 補充：
(拍肩) 小子別灰心, 我讀了八年化學也不是一帆風順的
聞道有先後, 術業有專精; 努力發掘自己的優點吧!
2010-09-22 6:36 am
My result of science is quite good in F2...................
F3 now.....................
F3 now.....................
2010-09-22 2:48 am
1a
the candle goes out
1b
because it uses up all the oxygen inside the tube
2a
rises one-fourth
2b
because the oxygen is used up
2c
because oxygen made up about 1/4 of the normal air
the candle goes out
1b
because it uses up all the oxygen inside the tube
2a
rises one-fourth
2b
because the oxygen is used up
2c
because oxygen made up about 1/4 of the normal air
收錄日期: 2021-04-19 23:16:33
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