text: how much heat is needed to change 50.0 g of water at 100.0 degrees to steam at 100.0 degrees?   wrong answer. the heat of fusion (transform ice to water) and heat of vaporization (water to steam) is different.  the heat of fusion for water is 334 j/g.  the heat of vaporization for water is 2260 j/g.   to calculate the heat needed:  heat required = 2260 j/g x 50 g = 113,000 j   i never understood the significant figures crap. maybe someone else can do that part.