When water evaporates at constant pressure, the sign of the change in enthalpy

A. is negative.

B. is positive.

C. depends on the temperature.

D. depends on the volume of the container.

E. does not exist; that is, the enthalpy change is zero.

B. is positive

H20 (l) - - > H20 (g)

when that happens, the heat is absorbed into the liquid to change the state of the liquid to gas; therefore, in order to change to a gaseous state, heat must be a reactant. and so enthalpy is increasing