Question

Sorting classifier uses a sink-and-float method to separate particles based on the

• A. Particle size
• B. Difference in terminal velocities
• C. Difference in the densities of the particles
• D. Centrifugal force

Hint:

Key Separation Mechanism Identifiers: - Screening Sieving \(\implies\) Separates primarily by Size. - Sedimentation Elutriation \(\implies\) Separates by Terminal Settling Velocity. - Sink-and-Float method \(\implies\) Separates primarily by Density.

Answer 1

The Correct Option is C

Concept: Mechanical separation techniques split a mixture of solid particles into distinct fractions based on physical characteristics such as size, shape, or density. A sorting classifier separates components using differences in their settling behaviors within a fluid medium. A prime example of this methodology is the sink-and-float separation method (also known as Heavy Media Separation). This technique uses a liquid medium with a precisely calibrated intermediate density (\(\rho_{\text{fluid}}\)) to separate two or more solid particulate components.

Step 1: Analyzing the underlying physics of the sink-and-float process.
When a mixture of solid particles with different densities is introduced into a fluid medium of density \(\rho_{\text{fluid}}\), the behavior of each particle is determined by the net balance between the downward force of gravity and the upward buoyant force, according to Archimedes' principle: \[ F_{\text{net}} = V \cdot g \cdot (\rho_{\text{particle}} - \rho_{\text{fluid}}) \]

Step 2: Evaluating particle trajectories based on density differences.
Let's look at the two possible cases for particle movement:
• Case 1 (Sink): If a particle's density is greater than the fluid medium (\(\rho_{\text{particle}} > \rho_{\text{fluid}}\)), the net force is downward, causing the particle to sink to the bottom.
• Case 2 (Float): If a particle's density is less than the fluid medium (\(\rho_{\text{particle}} < \rho_{\text{fluid}}\)), the net force is upward, causing the particle to rise and float on the surface.

Step 3: Concluding the separation property.
Because this technique relies directly on whether a particle's density is higher or lower than the liquid medium to separate components, it separates materials based on the difference in the densities of the particles. This matches Option (C).