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What was the conclusion drawn from the experiment performed by Joseph Priestley?
Option: 1
Animals can purify the air
Option: 2
Plants restore the air polluted by animals
Option: 3
Both a and b
Option: 4
None of these
Answers (1)
Exp. 1
- Joseph Priestley in 1770 performed a series of experiments that revealed the essential role of air in the growth of green plants.
- Priestley observed that a candle burning in a closed space – a bell jar, soon gets extinguished. Similarly, a mouse would soon suffocate in a closed space.
- He concluded that a burning candle or an animal that breathe the air, both somehow, damage the air.
- But when he placed a mint plant in the same bell jar, he found that the mouse stayed alive and the candle continued to burn.
- Priestley hypothesised as follows: Plants restore the air whatever breathing animals and burning candles remove.
Exp. 2
- Using a similar setup as the one used by Priestley, but by placing it once in the dark and once in the sunlight, Jan Ingenhousz (1730-1799) showed that sunlight is essential to the plant process that somehow purifies the air fouled by burning candles or breathing animals.
- Ingenhousz in an elegant experiment with an aquatic plant showed that in bright sunlight, small bubbles were formed around the green parts while in the dark they did not.
- Later he identified these bubbles to be of oxygen.
- Hence he showed that it is only the green part of the plants that could release oxygen.
-
Priestley hypothesised as follows: Plants restore the air whatever breathing animals and burning candles remove. Hence, the correct answer is option b.
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