The correct answer is a and b. Explanation & Key Takeaways: Properties of a Colloidal sol are- • Colloidal particles show the Tyndall effect as they scatter light. Small-sized colloidal particles cannot be seen with naked eyes but they are big enough to scatter a beam of light. • Colloidal particles show Brownian motion since the colloidal particles show random movement in the solution. • Hence the correct answer is a and b. Important Notes: • Tyndall effect • Tyndall effect is the phenomenon in which the particles in a colloidal solution scatter the beams of light that are directed at them • Brownian motion • Colloidal particles in a solution are continuously bombarded by the molecules of the dispersion medium on all sides. • As a result, the solution particles show random or zig-zag movements. • This random or zig-zag motion of the colloidal particles in solution is called Brownian motion or Brownian movement. Related Concepts: • Maxwell distribution • Maxwell-Boltzmann Distribution is a probability distribution used for describing the speeds of various particles within a stationary container at a specific temperature. • Van der Waals forces • Van der Waals force is a distance-dependent interaction between atoms or molecules. • They are comparatively weak and therefore more susceptible to disturbance. • The van der Waals force quickly vanishes when distances between interacting molecules increases. Important Notes: • Colloid Mixture • A colloid is a mixture in which one substance of microscopically dispersed insoluble particles is suspended throughout another substance. • A colloid is a heterogeneous mixture of a dispersed phase and a dispersion medium. • It appears as a homogeneous mixture to the naked eye. • The particle size varies from 1 to 100 nm (nanometers).