Problem 8 - Chemistry in 30 days

Question

Fog is an example of a colloid system of (a) Liquid particles dispersed in gas (b) Gas particles dispersed in gas (c) Solid particles dispersed in gas (d) Solid particles dispersed in liauid

Step-by-Step Solution

Answer

(a) Liquid particles dispersed in gas.

Step 1: Understand Colloids

A colloid is a mixture in which one substance of microscopically dispersed insoluble particles is suspended throughout another substance. It consists of a dispersed phase (the particles) and a continuous phase (the medium of dispersion).

Step 2: Identify the Phases in Fog

Fog is commonly observed as tiny droplets of water (liquid) dispersed in air (gas). Thus, in the case of fog, we have liquid particles dispersed in a gas medium.

Step 3: Match the Description with Options

Given the options, (a) describes 'liquid particles dispersed in gas', which is the correct characterization of fog.

Key Concepts

Dispersed Phase

In colloid systems, the dispersed phase is composed of the tiny particles distributed throughout another substance. These particles can vary widely in nature, including liquids, solids, or gases. The crucial aspect of these particles is that they are microscopic. This small size allows them to remain suspended in the continuous phase, creating a stable colloidal mixture.
Two things make the dispersed phase distinct in colloids:

• Size: Colloidal particles are larger than typical molecular species but too small to be seen with the naked eye. This size, generally ranging from 1 nanometer to 1 micrometer, allows these particles to be distributed throughout another substance.
• State: The dispersed phase can exist in different physical states. Example: in fog, the dispersed phase is liquid water droplets.

This dispersed nature enables colloids to have unique characteristics that are different from standard solutions or suspensions.

Continuous Phase

In the context of colloidal systems, the continuous phase is the medium in which the dispersed particles are suspended. It acts as a backdrop against which the dispersed particles are interspersed. The continuous phase is critical for the colloid's stability, as it allows the fine particles to remain evenly distributed without settling.
The continuous phase can also appear in different states:

• Gas: In fog, air serves as the continuous phase, supporting liquid water droplets.
• Liquid: Mayonnaise is an example where oil is dispersed in water acting as the continuous phase.
• Solid: In some gels, a solid matrix holds together a dispersed liquid or another solid.

Being the larger component, the continuous phase prevents the dispersed particles from clumping together, thus maintaining the colloidal structure.

Types of Colloids

Colloids are classified into various types based on the state of their dispersed and continuous phases. This classification helps us understand the diverse nature and behavior of different colloid systems.
Let's explore some common types:

• Sol: A solid dispersed in a liquid, like paint.
• Gel: A liquid dispersed in a solid, fairly common in foods like jelly.
• Aerosol: A liquid or solid dispersed in a gas, such as fog or smoke.
• Emulsion: A liquid dispersed in another liquid, which is immiscible, like milk.

By distinguishing between these types, we gain insight into how various everyday substances function. This understanding is essential for industries that depend on creating colloidal systems, such as food production, pharmaceuticals, and cosmetics.