Final answer:
The primary control on chemical reactions turning organic matter into hydrocarbons is temperature and pressure during catagenesis. Organic molecules break down to form hydrocarbons like oil and natural gas, which are used as major energy sources in society.
Step-by-step explanation:
The primary control on chemical reactions that convert organic matter to hydrocarbons is temperature and pressure conditions during the process called catagenesis. This process involves the conversion of organic matter buried in sedimentary basins over geological timescales. Through increased temperature and pressure, organic molecules break down to form oil and natural gas, which consist mainly of hydrocarbons. Catagenesis occurs following diagenesis (a series of processes that produce peat, lignite, and coal), and precedes metagenesis (which may result in the formation of graphite at highest temperatures).
The pathway of hydrocarbon generation often involves the transformation of organic matter from complex macromolecules—proteins, lipids, and carbohydrates—into simpler compounds. During this chemical evolution, hydrocarbons like methane (CH4), ethane (C2H6), and longer chain alkanes, as well as benzene (aromatic hydrocarbon), are generated, which can be trapped in subsurface geological formations to form petroleum reservoirs. The energy released during the combustion of hydrocarbons like methane and gasoline is fundamental to our society, powering vehicles, generating electricity, and heating homes.