Which one of the following processes is exothermic?

• A. Photosynthesis in plants
• B. Combustion of methane (CH_4)
• C. Melting of ice
• D. Evaporation of water

Answer: (B)

Verified step by step guidance

1. Understand the definition of an exothermic process: it is a process that releases heat to the surroundings, meaning the system loses energy.
2. Analyze each given process to determine whether it releases or absorbs heat:
3. - Photosynthesis in plants is an endothermic process because it requires energy (sunlight) to convert carbon dioxide and water into glucose and oxygen.
4. - Combustion of methane (CH_4) is a chemical reaction where methane reacts with oxygen to produce carbon dioxide and water, releasing energy in the form of heat and light, making it exothermic.
5. - Melting of ice and evaporation of water are physical changes that require heat input to overcome intermolecular forces, so both are endothermic processes.