10-3 Phase change

solid s/l liquid l/g gas 2.09 J/g0C --- 333.5 -------- 4.18 J/g0C ------2264----- 1.84 J/g0C J/g J/g solid s/l liquid l/g gas  

Section 1 As energy is applied to the sample of solid ice, its temperature rises from a negative value, to the melting point, 0ºC. The molecules are still in the solid phase, but they begin to “vibrate” more. Ice has a specific heat capacity of 2.09 J/gºC.

Section 2 At the melting point, which is the same as the freezing point, all energy added goes into breaking the bonds between the ice water molecules (“intermolecular forces”) and therefore the temperature doesn’t rise. The energy required to change a solid to a liquid is termed heat of fusion (∆Hfusion). Water has a ∆Hfusion = 6010 J/mole.  = ~ 334 J/g of water

Section 3 Heat energy now goes into kinetic energy of the liquid water molecules, thereby increasing the temperature. This continues until the boiling point, 100ºC. Liquid water has a specific heat capacity of 4.18 J/gºC.

Section 4 At the boiling point, which is the same as the condensation point, all energy goes into breaking the intermolecular forces between the liquid water molecules, and the temperature remains constant. The energy required to change a liquid to a gas is termed heat of vaporization (∆Hvaporization). Water has a ∆Hvaporization = 40790 J/mole. (~2264 J/g)

Section 5 Once again, the heat goes into KE of the gaseous molecules and the temperature rises. Water vapor has a specific heat capacity of 1.84 J/gºC.