= Solution
\b[A stable charge-stabilized dispersion has an interaction barrier large compared with $k_BT$.] In <DLVO theory>, the total pair potential combines attractive <Van der Waals forces> with repulsion from overlapping <electric double layers>. Similar surface charges raise the free energy of overlap; a sufficiently high positive barrier prevents thermally diffusing particles from reaching the deep primary minimum near contact.
Other stabilization mechanisms include <steric stabilization> by solvated surface chains and combined electrosteric protection by charged chains. Such contributions are additional to the simplest DLVO pair potential. Increasing salt shortens the <Debye length>, so double-layer repulsion becomes shorter-ranged and the protective barrier can decrease.
\Image[/past-exam-of-the-chemistry-course-of-the-year-4-of-the-natural-sciences-course-of-the-university-of-cambridge/2022/paper-2-colloidal-potentials.png]
{title=Original schematic DLVO stability, depletion attraction and brush scaling}
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