# How much energy is needed to change 1 g of ice at 0°C to water at 0°C?

##### 1 Answer

If you think about it for a moment---and it should be intuitive, you should recognize that ice changing into water is a **melting** event.

*Melting**is the opposite of fusion, or freezing.*

Hence, we should consider "latent heat of fusion", or **enthalpy of fusion**,

#color(green)(DeltabarH_("fus","H"_2"O") = "6.02 kJ/mol")#

*A natural melting event occurs at a constant temperature and constant pressure.*

At a constant pressure,

The "energy" you speak of is

#\mathbf(n_("H"_2"O")DeltabarH = q_p)# where

#n# is the number of#"mol"# s and#q_p# is in#"kJ"# .

The

#n_("H"_2"O") = 1 cancel("g H"_2"O") xx ("1 mol H"_2"O")/(18.015 cancel("g H"_2"O"))#

#= "0.0555 mol H"_2"O"#

Thus:

#color(blue)(q_p) = "0.0555 mol H"_2"O" xx "6.02 kJ/mol"#

#= "0.3342 kJ" = color(blue)("334.2 J")#

Since we have to supply heat energy *into* the system to melt the ice, the system *absorbs* energy. Thus, the sign of this answer should be **positive**.