What is characteristic of an endothermic reaction?

An endothermic reaction is characterized by the absorption of heat from the surroundings, which leads to a decrease in the temperature of the surroundings as the reaction occurs. This means that the surroundings gain energy in the form of heat. The significance of this energy absorption is crucial because it is the driving force behind many chemical processes and is used in various applications, such as cold packs that absorb heat to cause a cooling effect.

The other options do not accurately describe endothermic reactions. For instance, endothermic reactions do not produce heat; instead, they consume it. The heat change in these reactions is positive, reflecting the gain of energy, which is opposite to what is stated in the negative heat change option. Additionally, while endothermic processes can involve solid reactants, there is no restriction that limits them to only solid forms; they can include gaseous and liquid reactants as well. Thus, the defining feature of endothermic reactions is the gain of energy by the surroundings, confirming that option B is the correct choice.