Kinetic Properties of Colloids

• Kinetic properties of Colloids are related to the movement of colloidal particles due to thermal or external forces.
• Kinetic Properties of Colloids explain particle stability, transport, and dynamic interactions.
• These motions contribute to the stability and behavior of colloidal systems.

1. Brownian Motion

• Definition:

  • The random, zig-zag motion of colloidal particles due to continuous collision with molecules of the dispersion medium.

• Discovered by:

  • Robert Brown (1827)

• Factors affecting:

  • Particle size (smaller = more motion)
  • Temperature (higher = faster motion)
  • Viscosity of the medium

• Significance:

  • Prevents settling (adds to stability)
  • Evidence of molecular motion

2. Diffusion

• Definition:

  • Spontaneous movement of colloidal particles from a region of higher concentration to lower concentration.

• Note:

  • Much slower than in true solutions
  • Rate depends on particle size and medium viscosity

• Use:

  • Helps determine molecular weight of colloidal particles
  • Affects uniform distribution of particles

3. Sedimentation

• Definition:

  • The settling of colloidal particles under the influence of gravity or centrifugal force.
  • Normally very slow due to small size and Brownian motion
  • Accelerated using centrifugation

• Application:

  • Separation and purification
  • Determining particle mass or size via ultracentrifugation

4. Viscosity

• Definition:

  • The resistance to flow of a fluid, influenced by the presence of colloidal particles.
  • Lyophilic sols increase viscosity significantly
  • Lyophobic sols show minimal effect on viscosity

• Applications:

  • Estimating molecular size of polymers
  • Industrial formulations (paints, cosmetics, food)

Thank you for reading from Firsthope's notes, don't forget to check YouTube videos!