kolloïde

A colloid, also known as a colloidal dispersion or colloidal suspension, is a mixture in which one substance of extremely fine particles is dispersed evenly throughout another substance. The dispersed-phase particles have a size ranging from approximately 1 to 1000 nanometers. They are larger than atoms or molecules in a true solution but too small to be seen with the naked eye or to settle out. Examples include milk, fog, and smoke.

Colloidal systems are thermodynamically stable but kinetically stable. This means the dispersed particles do not spontaneously aggregate or settle out over time due to gravity, but they can be made to aggregate or separate by physical means like centrifugation. The particles in a colloid exhibit Brownian motion, a random movement caused by collisions with the molecules of the dispersion medium. This motion helps to keep the particles suspended.

Colloids are classified based on the physical state of the dispersed phase and the dispersion medium. Common types include aerosols (solid in gas or liquid in gas), foams (gas in liquid or solid), emulsions (liquid in liquid), sols (solid in liquid), and gels (liquid in solid). The properties of colloids, such as their optical properties (Tyndall effect, where light is scattered by the particles) and electrical properties (charge on the particles), are distinct from those of true solutions and suspensions. Colloidal chemistry is an important field with applications in many industries, including food science, pharmaceuticals, and materials science.