Check sibling questions

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.

  1. Process – A is a chemical change.
  2. Process – B is a chemical change.
  3. Both processes A and B are chemical changes.
  4. None of these processes is a chemical change.  



  • Digestion of animal waste results in the production of biogas ( a new substance).
  • Biogas being burnt as fuel is accompanied by the evolution of heat and energy .
  • Since neither of them can be reversed , both are chemical changes .

So, the correct answer is (iii) .

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo