A Level Chemistry OCR Practice Exam

Which of the following describes the process of biodegradation?

1. A chemical reaction that produces energy

2. The breakdown of materials by living organisms

3. A physical change in substance composition

4. A reaction involving synthetic chemicals

The correct answer is: The breakdown of materials by living organisms

The process of biodegradation is accurately described as the breakdown of materials by living organisms. This biological process involves microorganisms, such as bacteria and fungi, that decompose organic matter into simpler substances. As these organisms consume the materials, they transform complex compounds into simpler compounds such as carbon dioxide, water, and biomass. This process is essential for recycling nutrients in ecosystems and helps in the management of waste materials, including food scraps and agricultural waste. In contrast, the other options do not capture the essence of biodegradation. For example, a chemical reaction that produces energy is a broader concept that can include various types of reactions, not specifically tied to the breakdown of organic materials by living organisms. A physical change refers to alterations in the state or appearance of a substance without changing its chemical composition, which does not apply to the biochemical processes involved in biodegradation. Lastly, a reaction involving synthetic chemicals typically relates to man-made substances rather than the natural breakdown processes facilitated by living organisms.