24 Questions
What is the main cause of non-wetting in a liquid when solid particles are added?
Insufficient dispersion of solid particles in the liquid
What type of forces lead to attraction between particles in a liquid?
Van der Waals forces
What causes the overall free energy of a system to increase when particles are dispersed into a liquid?
Creation of a large interfacial area
What is the main factor determining the stability of a suspension in a liquid?
Balance of attractive & repulsive interactions
What can greatly affect the zeta potential of particles and ultimately the stability of the system?
Electrolytes, pH, and other molecules that can adsorb to the interface
What characterizes deflocculated particles?
Residing in primary minimum, high zeta potential, and repulsive forces exceeding attractive forces
What does the sedimentation parameter F=1 indicate?
Flocculation equilibrium
What is the Stokes Equation used for?
Calculating the rate of sedimentation/creaming for spherical particles in a dilute suspension
What does the sedimentation rate v in the Stokes Equation depend on?
Particle size, density, and viscosity of the liquid
What are the limitations of the Stokes Equation?
Applies only to spherical particles in a very dilute suspension
How can flocculation be controlled?
By adding electrolytes and/or polymers to bring about flocculation
What causes separation of phases in sedimentation and creaming?
Gravitational forces
What is the main factor that defines colloidal stability?
Prevention of particle aggregation
What is the role of weak intermolecular forces in colloidal systems?
Cause flocculation
How can aggregation in dispersions be prevented?
Introducing repulsive interactions
What is the significance of zeta potential in colloidal stability?
Measures surface potential and crucial for stability
What influences the electrical repulsion between particles in dispersions?
Presence, concentration, and valence of counterions
What plays a critical role in particle stability by forming repulsive barriers?
Electric double layer
Where is the zeta potential measured?
At the shear plane
What is the conventional belief about the position of the shear plane?
Close to the Stern plane
What influences the zeta potential?
The potential-determining ion and the counterion
What is the role of steric repulsive barriers in dispersions?
Prevent formation of hard cakes
What is the significance of the electric double layer in colloidal stability?
Plays a critical role in particle stability
What is the purpose of the repulsive interactions introduced in dispersions?
Overcome the thermodynamic tendency for aggregation
Study Notes
Colloidal Stability and Particle Interactions
- Particles in a dispersion system tend to form agglomerates to decrease surface area, leading to phase separation
- Flocculation occurs due to weak intermolecular forces, while aggregation is driven by stronger forces
- Colloidal stability is defined by the prevention of particle aggregation in dispersions
- To prevent aggregation, repulsive interactions must be introduced to overcome the thermodynamic tendency
- Electric and steric repulsive barriers can prevent the formation of hard cakes in dispersions
- Zeta potential measures the surface potential of particles and is crucial for stability
- Electrical repulsion between particles is influenced by the presence, concentration, and valence of counterions
- The electric double layer, including the Stern plane and shear plane, plays a critical role in particle stability
- Zeta potential is dependent on the amount of absorbed counterions and is measured at the shear plane
- Zeta potential is important for understanding and ensuring the stability of dispersed systems
- The potential-determining ion and the counterion influence the zeta potential
- The exact position of the shear plane is not known, but it is conventionally believed to be close to the Stern plane
Test your understanding of colloidal stability and particle interactions with this quiz. Explore concepts such as agglomeration, flocculation, and aggregation, and learn about the crucial role of zeta potential and electric double layer in preventing particle aggregation in dispersions.
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