Graph 1: This is the curve for pure water or very low electrolyte concentration. The Repulsion term dominates and the overall interaction energy becomes positive. The energy barrier is very high and hence, the colloid remains stable.

Graph 2: The secondary minimum starts appearing but the Energy barrier is still very high, so the colloid is kinetically stable. i.e. there may be a little flocculation but true coagulation is difficult.

Graph 3: The Energy barrier is lowered further and the coagulation may increase. If the barrier is sufficiently low, than the particles may even be able to cross it due to their Thermal energy.

Graph 4: Energy barrier has become zero, and fast coagulation is possible. The concentration at this point is called ‘Critical Coagulation Concentration (CCC)’ at which coagulation can occur spontaneously. Hence, the colloid becomes unstable

Graph 5: As the concentration of ions has become very large, there is a large attractive Van-der Waals force, due to which there is no barrier and very fast coagulation takes place.

We should remember that LW component cannot be altered by changing any parameter as Hamaker constant is fixes for a given set of interacting bodies.