Which of the following best describes an exothermic process?

An exothermic process is defined by the release of heat into the surroundings. This means that during the process, energy is given off as thermal energy, often causing the temperature of the surrounding environment to increase. This release of heat can occur in various chemical reactions, such as combustion, where energy stored in chemical bonds is transformed into heat and light.

The characteristics of an exothermic process make option B the most accurate description. The energy is not absorbed from the surroundings; rather, it flows outwards, leading to an overall decrease in the internal energy of the system involved in the reaction.

In contrast, an endothermic process would absorb heat from the surroundings and cool them down, which is why option A does not fit the definition of exothermic. Additionally, option C describes a scenario of no energy exchange, which contradicts the nature of exothermic reactions that are fundamentally characterized by energy release. Lastly, option D is misleading as exothermic processes can occur in solids, liquids, and gases, not just within gaseous states. Thus, the correct understanding of exothermic processes is best captured by the idea of heat being released into the surroundings.