Question

Assertion: Colloidal solutions do not show Brownian motion. Reason: Brownian motion is responsible for stability of sols.

Short answer

The assertion is false and the reason is true.

Step-by-step solution

Identifying the Assertion

The assertion states that colloidal solutions do not show Brownian motion. To tackle this, we first need to understand what Brownian motion is. It refers to the random, irregular movement of particles suspended in a fluid (liquid or gas) resulting from their collision with the fast-moving molecules in the fluid. Colloidal particles are small enough to exhibit this kind of motion.

Analyzing the Reason

The reason provided is that Brownian motion is responsible for the stability of sols. 'Sols' refer to colloidal suspensions; hence they inherently relate to our assertion since they contain colloidal particles that are known for exhibiting Brownian motion, which helps prevent sedimentation.

Connecting Brownian Motion to Stability

Brownian motion in colloids helps in preventing the colloidal particles from settling down due to gravity, thereby contributing to the stability of the colloidal solution. This movement keeps the particles suspended and evenly distributed throughout the solution.

Evaluating the Assertion and Reason

Given that colloids do show Brownian motion, which is crucial for maintaining the stability of sols, the assertion that 'colloidal solutions do not show Brownian motion' is incorrect. The reason, however, correctly links Brownian motion to the stability of colloidal solutions.

Conclusion Based on Evaluation

Since the assertion is false, and the reason is true but does not support the false assertion, we conclude that the assertion is incorrect and does not reflect the true nature of colloidal solutions, while the reason correctly explains Brownian motion's role in stability.

Key concepts

Brownian Motion

Brownian motion is an essential concept when discussing colloidal solutions. It describes the random, jittery movement of particles suspended within a fluid such as a liquid or gas. This movement results from collisions between the colloidal particles and the molecules of the surrounding fluid. Colloidal particles are small enough to engage in such dynamic motion, which is typically more pronounced in smaller particles and higher temperatures. This movement not only illustrates the kinetic properties of particles in a suspended state but also plays a crucial role in various natural and industrial processes.

The unpredictable path taken by these particles has been extensively studied since its discovery and has profound implications in physics and chemistry. This continuous jostling keeps the colloidal particles from aggregating, meaning they remain evenly dispersed throughout a solution. Such motion not only provides fascinating insights into particle dynamics but is also a cornerstone of understanding how colloidal solutions behave and stabilize over time.

Stability of Sols

The stability of sols, or colloidal solutions, is vital for their function and application in numerous fields. This stability is greatly influenced by the characteristics of Brownian motion within the solution.

Colloids, when stable, do not allow particles to settle or clump due to gravitational forces. Instead, colloidal particles remain suspended, thanks to the constant motion caused by Brownian dynamics. This ensures that the mixture remains homogenous and that particles are evenly spaced throughout the liquid.

Several factors contribute to this stability:

• Particle Charge: Similar charges on particles can lead to repulsion, preventing clumping, which promotes stability.
• Brownian Motion: As a constant swirling force, it ensures particles continue to move across the medium.

Understanding how Brownian motion stabilizes sols helps chemists and engineers design advanced materials and products, from paints to medicines, by ensuring that sol particles maintain their uniform dispersion over time.

Colloidal Particles

Colloidal particles are the small, suspended masses within a colloidal solution, also known as a sol. These particles can range in size from 1 nanometer to 1 micrometer, placing them between true solutions and suspensions in terms of particle dimension.

These particles play a significant role in defining the properties and behavior of the colloid.

• Size and Surface Area: The small size and high surface area of colloidal particles enable them to remain suspended and resist sedimentation.
• Charge: They usually acquire a charge when dispersed in a sol, aiding in interaction and repulsion, thereby preventing aggregation.
• Movement: Due to Brownian motion, these particles exhibit constant unpredictable movement that reinforces their stable disposition within the sol.

The intrinsic qualities of colloidal particles make them versatile in various applications, including catalysis, drug delivery, and emulsification processes, aligning them as crucial agents in scientific and industrial methodologies.

Sedimentation Prevention

Sedimentation, the process by which particles settle down in a fluid, is a common challenge in maintaining the homogeneity of mixtures. In colloidal solutions, sedimentation needs to be actively prevented to ensure the stability and utility of the sol.

This prevention is achieved primarily through Brownian motion. The perpetual and random movement of colloidal particles, driven by collisions with solvent molecules, counteracts the downward settling due to gravity. In addition to Brownian motion, sedimentation is also hindered by other factors:

• Particle Size: Smaller particles are less likely to settle due to their ability to remain buoyant in the fluid medium.
• Charge Repulsion: The like-charges of colloidal particles create repulsive forces that prevent aggregation and settling.

By preventing sedimentation, the colloidal particles stay suspended and uniformly distributed. This ensures that the physical and chemical properties of the sol are consistently maintained for effective application. From pharmaceuticals to food products, understanding how to prevent sedimentation enhances the formulation and quality of colloidal-based mixtures, making it an indispensable aspect of material science.