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

• A. Neutralization of hydrochloric acid with sodium hydroxide
• B. Photosynthesis in plants
• C. Freezing of water
• D. Combustion of methane

Answer: (B)

Verified step by step guidance

1. Understand the definition of an endothermic reaction: it is a chemical reaction that absorbs energy from its surroundings, usually in the form of heat.
2. Analyze each option to determine whether it absorbs or releases heat:
3. 1. Neutralization of hydrochloric acid with sodium hydroxide is an exothermic reaction because it releases heat when an acid and base react to form water and salt.
4. 2. Photosynthesis in plants is an endothermic process because it requires energy input (sunlight) to convert carbon dioxide and water into glucose and oxygen.
5. 3. Freezing of water is an exothermic process because it releases heat as water changes from liquid to solid.
6. 4. Combustion of methane is an exothermic reaction because it releases heat and light as methane burns in oxygen.