What is a dispersion?
A dispersion is a collection of small particles in a matrix. It has at least two phases:
- Dispersed phase
- Continuous medium
The definition of a continuous phase is that if we start from any point in a continuous phase, we can return to the same point by moving along the same phase only. On the other hand, to go from one point to another of a dispersed phase, we must necessarily cross the continuous phase. For example, soap bubbles in water, where bubbles form the dispersed phase and water is the continuous phase.
What is a stable dispersion?
A stable dispersion is one in which the dispersed particles remain single entities and do not coagulate. Coagulation leads to phase splitting and a complete change in the properties of the system. In most situations we do not want coagulation to occur but there in certain situations it might be beneficial. For example, during purification of water, we want coagulation to occur so that all the impurities come together and can be disposed of easily.
Types of stabilities
- Thermodynamic stability (Of Theoretical Importance)
- Kinetic stability (Of Practical Importance)
A system is called thermodynamically unstable when there exists a state where the system will have lower energy than it currently has. A dispersion can be thermodynamically unstable, but can still be kinetically stable. If in a dispersion (even if it is thermodynamically unstable) the particles do not coagulate for a very long period of time, it is, for all intents and purposes, a stable dispersion, and is called kinetically stable.
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