Which of the following is an example of an endothermic reaction?

• A. Freezing of water
• B. Condensation of steam
• C. Photosynthesis in plants
• D. Combustion of methane

Answer: (C)

Verified step by step guidance

1. Understand the definition of an endothermic reaction: it is a process that absorbs heat energy from the surroundings, resulting in a net intake of energy.
2. Analyze each option to determine whether heat is absorbed or released:
3. Freezing of water releases heat to the surroundings (exothermic), so it is not endothermic.
4. Condensation of steam releases heat as steam changes to liquid water (exothermic), so it is not endothermic.
5. Photosynthesis in plants requires energy input from sunlight to convert carbon dioxide and water into glucose and oxygen, meaning it absorbs energy (endothermic).
6. Combustion of methane releases heat energy as it burns (exothermic), so it is not endothermic.