Question

why does steam posses more energy than water at hundred degree Celsius

Answer 1

jus because steam has more latent heat of fusion than that of water at 100° C

Answer 2

The phase change itself requires a tremendous amount of energy. The scale is actually sort of amazing to me. Liquid water at 100 C has 419 kJ/kg. Just converting it to a vapor without any temperature change requires 2257 kJ/kg, more than 5 times the original energy. The reason why is that there are intermolecular forces that attract one water molecule to another. You have to put in enough energy to overcome this attractive force.