Final answer:
Micelle formation is endothermic because it requires energy to disrupt the intermolecular interactions in the solute and solvent, which is greater than the energy released from the interactions between the solute particles and solvent in step 3 of solvation.
Step-by-step explanation:
The question asks why micelle formation is endothermic. Micelle formation is endothermic because it requires energy to overcome the intermolecular forces of both the solute and the solvent. When detergents or soaps form micelles, the process involves enthalpy changes during solvation.
Specifically, micelle formation goes through three steps of enthalpy changes: ΔH₁, ΔH₂, and ΔH₃. Both ΔH₁ and ΔH₂ are positive, meaning they are endothermic processes that require the input of energy to break intermolecular interactions in the solute and solvent respectively. ΔH₃, involving interactions between solute and solvent, usually releases energy (exothermic).
However, for micelle formation to be endothermic overall (ΔH soln > 0), ΔH₃ must be smaller in magnitude than the sum of ΔH₁ and ΔH₂ making the overall process require an input of energy from the surroundings.