SCIENCE EXPERIMENT REPORT AIM : To show the percentage of oxygen in air. HYPOTHESIS : The percentage of oxygen in air is about 20%. APPARATUS AND MATERIALS : Glass trough, gas jar stand, metre ruler, candle, marker pen, matches, plasticine. Figure 1 VARIABLE : 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 PROCEDURES : 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. . 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) cmPercentage of oxygen in air= (15-12) cm x 100% 15cm 12. Write a complete report on this activity. STEPS : 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). 6. The gas jar was removed and the candle was lighted. 7.The inverted gas jar was carefully replaced over the lighted candle. 8.
The changed of flame of the candle was observed. 9. When the flame was extinguished, the water level was marked on the gas jar (Figure 2). 10. The height of the air column in the gas jar was measured. (12 cm ) 11.
The results of my activity was recorded. Height of the air column at the beginning of the activity: 15 cm Difference in heights of the air column: (15-12) cm x100% 15 cm 12. A complete report on this activity was written. RESULT: Figure 2 DICUSSION: 1.What happened to the flame of the candle at the end of the activity? Why? The flame of the candle extinguished at the end of the activity and the water level go up to the first level. Because the burning of the candle used up the oxygen in the gas jar.
2. What conclusion can you make from your observations? Oxygen is need for combustion. 3. Using the data obtained from the activity, calculate the percentage of oxygen in the air. Percentage of oxygen in air:(15-12) cm x100% 15 cm = 3 cm x100% 15 cm =1 cm x100% 5 cm = 20% CONCLUSION: The percentage of oxygen in air is about 20%
