Difficulty: Easy
Correct Answer: 0.01 to 0.10 microns
Explanation:
Introduction / Context:
Brownian motion is the random thermal movement of small particles suspended in a fluid. It becomes important when designing colloid separation processes, ultrafiltration, and nanoparticle characterization, where gravity settling is minimal.
Given Data / Assumptions:
Concept / Approach:
As particle diameter decreases, the gravitational settling velocity (Stokes regime) decreases with d^2, while thermal agitation remains significant. In the submicron range (tens of nanometers to about 0.1 micron), Brownian diffusion dominates, countering sedimentation and leading to stable suspensions absent aggregation.
Step-by-Step Solution:
Verification / Alternative check:
Colloid science texts define colloids roughly 1 nm to 1 μm, with strongest Brownian effects below ~0.1 μm, consistent with the given range.
Why Other Options Are Wrong:
Common Pitfalls:
Assuming turbidity stability at micrometer scales without considering flocculation; interparticle forces and surfactants also affect suspension stability.
Final Answer:
0.01 to 0.10 microns
Discussion & Comments