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Class 7
Science
Physical and Chemical Changes
anaerobic bacteria digest animal waste and produce...

Question:
Anaerobic bacteria digest animal waste and produce biogas (Change – A). The biogas is then burnt as fuel (Change – B). The following statements pertain to these changes. Choose the correct one.

(i) Process – A is a chemical change.
(ii) Process – B is a chemical change. (iii) Both processes A and B are chemical changes.
(iv) None of these processes is a chemical change.

Answer:

(iii) Both process A and B are chemical change.
Anaerobic bacteria are those which works in the absence of oxygen. Burning the biogas as fuel is a chemical change because it is an irreversible process. Anaerobic bacteria digest animal waste and produce biogas as the final product in the absence of oxygen. Biogas is a natural gas, which is produced by bacteria.

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