To show the percentage of oxygen in air.
The percentage of oxygen in air is about 20%.
APPARATUS AND MATERIALS :
Glass trough, gas jar stand, metre ruler, candle, marker pen, matches, plasticine.
i. kept constant : the size of the candle
ii. manipulated: the amount of oxygen inside the gas jar iii. responds: the level of water in the gas jar
1. Use some plasticine to fix a candle to the gas jar stand in the trough. (Make sure that the length of the candle is nearly half the length of the gas jar. 2. Fill the trough with water.
3. Invert a gas jar over the candle.
4. Mark the water level on the gas jar.
5. Measure the height of the air column in the gas jar (15 cm). 6. Remove the gas jar and light the candle.
7. Carefully replace the inverted gas jar over the lighted candle. 8. Observe what happens to the flame of the candle.
9. When the flame goes out, mark the water level on the gas jar (Figure 1). 10. Measure the height of the air column in the gas jar (12 cm). 11. Record all results of my activity.
Height of the air column at the beginning of the activity : 15 cm Height of the air column at the end of the activity : 12cm Difference in heights of the air column : (15-12) cm
Percentage of oxygen in air= (15-12) cm x 100%
12. Write a complete report on this activity.
1. Some plasticine were used to fix a candle to the gas jar stand in the trough. (found that the length of the candle is nearly half the length of the gas jar. 2. The glass trough was filled with water.
3. A gas jar was inverted over the candle.
4. The water level was marked on the gas jar.
5. The height of the air column in the gas jar was measured (15 cm)....