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.

• A. Process – A is a chemical change
• B. Process – B is a chemical change
• C. Both processes A and B are chemical changes
• D. None of these processes is a chemical change

Answer 1

The correct option is C

Both processes A and B are chemical changes

The correct option is C.

Explanation of correct option:

1. A substance is said to go through a physical change when only the physical characteristics like size, shape, colors, appearance, or state of the substance change.
2. On the other hand, a substance is said to go through a chemical change when the chemical characteristics of a substance change. As a consequence, there is either breaking or formation of atomic bonds at the molecular level.
3. In the question, both change A and change B are chemical changes.
4. Both the reactions are irreversible and result in the formation of novel substances.
5. A chemical change is demonstrated by the decomposition process, that is, changes are involved in the composition of the components taking part. As a consequence, process A is an example of chemical change.
6. During the burning of biogas, it results in a chemical change, that is, resulting in the generation of new products.

The following are the reactions taking place in A and B:

$\mathrm{Biogas}\stackrel{\mathrm{burning}}{\to }\mathrm{CO}2+\mathrm{other}\mathrm{substances}$

Final answer: Both processes A and B are chemical changes.