Useful substances obtained from petroleum and natural gas.
Explanation
Petrochemicals are chemical products derived from petroleum (crude oil) and natural gas. They serve as the fundamental building blocks for the chemical industry and are utilized to produce a vast array of synthetic materials used in daily life.
Option Analysis:
- Chemical substances derived exclusively from coal mining. is Incorrect: While chemicals can be derived from coal (coal chemicals), the specific term "petrochemicals" refers to substances derived from petroleum and natural gas sources.
- Useful substances obtained from petroleum and natural gas. is Correct: Petrochemicals are defined as useful substances obtained from petroleum and natural gas. They are used extensively in the manufacture of detergents, synthetic fibres (such as polyester, nylon, and acrylic), polythene, and other man-made plastics.
- Solvents used to extract fossil fuels from rocks. is Incorrect: Petrochemicals are the resulting chemical feedstocks or products, not the solvents used in the extraction process of fossil fuels.
- Residues left after the combustion of natural gas. is Incorrect: Residues left after combustion are typically waste products (such as carbon dioxide and water vapour), whereas petrochemicals are valuable raw materials obtained through refining and chemical processing (such as cracking).
Key Takeaway:
Petrochemicals are industrial chemicals derived from petroleum and natural gas, serving as the primary raw materials for manufacturing synthetic fibres, plastics, and detergents.