The correct answer is option 2: steam has an additional heat known as latent heat of vaporization.

Option 1 is incorrect because both steam and water at 100°C are in the gaseous state. The state of matter does not determine the effectiveness of heating.

Option 3 is incorrect because both steam and water have hydrogen bonds. Hydrogen bonds exist between water molecules regardless of whether they are in the liquid or gaseous state.

Option 4 is incorrect because the transfer of heat from steam and water would depend on factors such as temperature difference and thermal conductivity. It cannot be generalized that the transfer of heat from steam is easier than water.

The reason why steam is more effective in heating than water at the same temperature is that steam has an additional heat known as latent heat of vaporization. Latent heat is the energy required to change a substance from one state to another without a change in temperature. When water vaporizes into steam, it absorbs a significant amount of heat energy from its surroundings. This latent heat of vaporization makes steam at 100°C more effective in transferring heat compared to water at the same temperature.