Why does solution formation require energy?
In order for a solute to dissolve, the bonds between solute particles need to be broken. Energy is required for a solute to break its bonds.
When you are forming a solution you need to break down the solute into its particles. The solute is the solid substance that you are dissolving.
Bond breaking requires energy as the solute is relatively stable in its solid form. If you were to increase the energy of the solution by increasing the temperature, formation of the solution would happen faster as the the solute particles will have enough energy to break their bonds.