24 Questions
What type of forces are responsible for the attraction between particles?
Van der Waals forces
What physical instability problem arises when solid particles don’t disperse uniformly in a liquid?
Non-wetting
What determines the stability of a suspension?
Balance of attractive & repulsive interactions
What leads to the system becoming thermodynamically unstable when particles are dispersed into a liquid?
$\Delta G = \gamma \Delta A$
Which type of system is characterized by particles residing in the primary minimum, having a high zeta potential, and settling slowly?
Deflocculated system
What effect does the addition of electrolytes and/or polymers have on the zeta potential of particles in solution?
Decreases the zeta potential
What is the sedimentation volume when flocculation equilibrium is reached?
1
What does the Stokes Equation describe?
Rate of sedimentation/creaming for spherical particles in a liquid
What is the relationship between the rate of sedimentation/creaming and particle size according to the Stokes Equation?
Rate of sedimentation/creaming is proportional to the square of the particle size
What is the limiting condition for the Stokes Equation to apply?
Spherical particles in a very dilute suspension
What happens to the sedimentation volume when an appropriate amount of flocculating agent is added to a deflocculated system?
Sedimentation volume increases
What is the effect of adding counterions/steric barriers in a flocculated system?
They act as a bridge between particles and weakly bond them
What is colloidal stability defined as?
Prevention of particle aggregation in dispersions
What type of interactions must be introduced to prevent aggregation?
Repulsive interactions
What does zeta potential measure?
Surface potential of particles
What influences the electrical repulsion between particles?
Presence, concentration, and valence of counterions
What plays a critical role in particle stability?
Electric double layer
What is the purpose of electric and steric repulsive barriers in dispersions?
Prevent the formation of hard cakes
What is the conventional belief about the position of the shear plane?
Close to the Stern plane
What is the role of the potential-determining ion and the counterion?
Influence the zeta potential
What is the difference between flocculation and aggregation?
Flocculation is due to weak forces, while aggregation is driven by stronger forces
What is the significance of the zeta potential in dispersed systems?
Important for understanding and ensuring stability
What tends to happen to particles in a dispersion system if they form agglomerates?
Phase separation
What is the key factor in preventing the formation of hard cakes in dispersions?
Repulsive interactions
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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