Which of the following phase changes involves the transfer of heat from the surroundings to the system?
a)CH4(g) → CH4(4), because CH, molecules in the gas phase must absorb energy in order to move closer together, thereby increasing the intermolecular attractions in the solid state.
b) CO2(g) → CO₂(s), because CO2 molecules in the gas phase must absorb energy in order to move closer together, thereby increasing the intermolecular attractions in the liquid state.
c)H2O(l) → H2O(s), because H₂O molecules in the liquid phase must absorb energy in order to create a crystalline structure with strong intermolecular attractions in the solid state.
d)NH3(l) → NH3(g), because NH3 molecules in the liquid phase must absorb energy in order to overcome their intermolecular attractions and become free gas molecules.