What is the change of state described in the experiment to determine the molar heat of fusion of ice?
1) 1 mol H₂O (s) + molar heat of fusion → 1 mol H₂O (l)
2) 1 mol H₂O (l) + molar heat of fusion → 1 mol H₂O (s)
3) 1 mol H₂O (s) + molar heat of vaporization → 1 mol H₂O (l)
4) 1 mol H₂O (l) + molar heat of vaporization → 1 mol H₂O (s)