question_answer

  Why does the burning candle in bell jar A stop burning before the candle in bell jar B? Both bell jars are placed near a window in  strong sunlight.

Answer:

                    Oxygen gas is essential for burning. In bright sunlight, the potted plant in bell jar B produces oxygen during the process of photosynthesis. The level of oxygen in bell jar B is therefore higher, so the candle burns for a longer time as more oxygen gas is available. During the process of burning, oxygen gas is used up, so eventually the candle is extinguished.     (2)