Question

Write the experiment of the bell jar and pudina plant, performed by Priestly to prove that air plays a key role in photosynthesis.

Answer 1

Hint:- Joseph Priestly carried out several experiments in his lifetime and is credited with the discovery of the photosynthetic process. He also described through various experiments that oxygen is required by the living organism and is an important air required for photosynthesis.

Complete step-by-step solution:-
The discovery of oxygen as an essential and important gas was done by Priestley. He showed through a series of well designed experiments that plants and animals require a gas known as oxygen. His famous experiment is known as the bell jar experiment.
The experiments were done using a bell jar, a candle, a mouse and a plant. In the first step, he introduced a candle and along with the candle, he put a mouse in the sealed jar. He observed that after some time, the candle went out and the mouse died of suffocation. In the next step, he put a pudina or mint plant along with the candle and the mouse inside the sealed bell jar. This time , he observed that the mouse did not die and the candle was burning too. He realized that the plant which was introduced inside the sealed bell jar somehow managed to balance the air inside the jar which avoided the mouse to die.
He concluded from his experiment that the gas which was present in the jar when a plant was kept with the mouse was oxygen gas. The mouse could survive only when there was the plant inside the jar or the jar was opened for a frequent time for fresh air. When the burning candle was kept inside the jar along with the mouse, the gas was not present due to which the mouse died. After some time the candle went out and released smoke. He then concluded that the fire needed some kind of gas to burn and it is the air or oxygen that allowed the fire to burn.
Thus, it was concluded that oxygen was the main element that allows the burning of the flame. In a sealed jar, there was not enough oxygen for the flame to burn. The flame went out to release carbon dioxide which killed the mouse. But due to the plants, the carbon dioxide present in the jar was absorbed and oxygen was released which is needed by all animals to survive.

Note:- In a series of classic experiments, Priestley demonstrated the presence and effects of the air or oxygen gas. In this experiment, he used a bell jar, a candle, a mouse and a pudina or mint plant. He showed through his experiment that in a closed environment, the candle could not burn and release harmful gas in which animals cannot survive. But when a plant is introduced in it, the plant absorbs the harmful gases to release oxygen that is needed for combustion and respiration in living organisms.