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


Process-A is a chemical change and process B is a physical change.


Process-B is a chemical change and process A is a physical change.


Both processes A and B are chemical changes.


None of these processes is a chemical change.

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Correct option is C)

 Physical Change: Properties like size, shape, state (solid, liquid, or gas), temperature, pressure, etc., are physical properties. Those changes in which only physical properties of a substance change are called physical changes. There is no change in chemical composition.
Chemical Change: The change in which a new substance is formed and the chemical composition of a substance are changed is called a chemical change. A substance loses its identity in a chemical change and cannot get back into its original form.

 Change A and change B both are chemical changes. As both the reaction are irreversible and they lead to the formation of new substances. There is also a change in the chemical properties of the reactants in both processes A and B.
Animal waste Bio gas ()                                                                                                                                                                                                                                                                                                                                       
Bio gas 

according to given explanation both processes A and B are chemical changes.
Hence, correct option is C.

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