Which of the following best describes an endothermic reaction?

• A. It releases energy into the surroundings
• B. It requires a continuous supply of energy
• C. It occurs spontaneously at room temperature
• D. It produces heat as a byproduct

Answer: (B)

An endothermic reaction is characterized by the absorption of energy from its surroundings, which is required for the reaction to take place. This means that an ongoing input of energy, often in the form of heat, is necessary to allow the reaction to progress. In practical terms, this is often observed in processes such as photosynthesis or the dissolution of certain salts in water, where energy is absorbed, resulting in a decrease in temperature of the surroundings.

The other choices do not accurately describe endothermic reactions. For example, an endothermic reaction does not release energy into the surroundings, nor does it typically occur spontaneously at room temperature without additional energy input. Additionally, it does not produce heat as a byproduct; instead, it consumes heat during the process. Thus, the requirement for a continuous supply of energy is the defining characteristic of endothermic reactions.