The correct answer is Endothermic Reaction. The conversion of water into steam involves the absorption of heat energy to overcome the intermolecular forces holding the water molecules together in the liquid state. This process is endothermic because it requires energy input.

Spontaneous Reaction is incorrect because the transition from water to steam requires energy input and occurs spontaneously only when heat is supplied. Exothermic Reaction is incorrect as it implies that energy is released, which is not the case in this scenario. Reversible Reaction is misleading in this context because while the phase change can be reversed, the process itself involves specific energy and entropy changes that are characteristic of endothermic reactions.

The conversion of water into steam at its boiling point is not spontaneous under standard conditions. It requires the input of energy to overcome intermolecular forces.

This is incorrect because the conversion of water into steam is an endothermic process, where heat is absorbed to facilitate the phase change from liquid to gas.

While the process of converting water to steam can be reversed by cooling the steam back to water, the phase transition itself involves changes in energy and entropy that define the conditions under which it occurs, but it is not inherently reversible without external control.

This is the correct answer as the conversion of water into steam requires the absorption of heat, making it an endothermic process. Heat energy is needed to break the hydrogen bonds between water molecules in the liquid state, allowing them to move freely as gas.