Problem 171 - A Complete Resource Book in Chemistry for JEE Main

Question

$$ \begin{aligned} &\text { Match the following }\\\ &\begin{array}{ll} \hline \text { Column-I } & \text { Column-II } \\ \hline \text { (a) Butter } & \text { (p) Dispersion of liquid in liquid } \\ \text { (b) Pumice } & \text { (q) Dispersion of solid in liquid } \\ \text { stone } & \\ \text { (c) Milk } & \text { (r) Dispersion of gas in solid } \\ \text { (d) Paints } & \text { (s) Dispersion of liquid in solid } \\ \hline \end{array} \end{aligned} $$

Step-by-Step Solution

Answer

(a)-(s), (b)-(r), (c)-(p), (d)-(q)

Step 1: Understanding Dispersion Types

Before matching the items from Column-I to Column-II, it's important to understand the different types of dispersions. The main types are: - Dispersion of liquid in liquid, - Dispersion of solid in liquid, - Dispersion of gas in solid, - Dispersion of liquid in solid.

Step 2: Analyzing Butter (Column-I: a)

Butter is a mixture where liquid (fat) is dispersed in solid (milk solids when cooled). This matches the description of 'dispersion of liquid in solid'.

Step 3: Analyzing Pumice Stone (Column-I: b)

Pumice stone contains gas bubbles trapped within a solid matrix. This fits the 'dispersion of gas in solid' category.

Step 4: Analyzing Milk (Column-I: c)

Milk is an emulsion which consists of fat globules dispersed in water, making it a 'dispersion of liquid in liquid.'

Step 5: Analyzing Paints (Column-I: d)

Paints commonly consist of pigment particles suspended in a liquid medium, which identifies as 'dispersion of solid in liquid.'

Step 6: Matching Items

Based on our analysis: - (a) Butter matches with (s) Dispersion of liquid in solid - (b) Pumice stone matches with (r) Dispersion of gas in solid - (c) Milk matches with (p) Dispersion of liquid in liquid - (d) Paints match with (q) Dispersion of solid in liquid

Key Concepts

Dispersion of Liquid in Liquid

When we discuss the dispersion of liquid in liquid, we're typically referring to mixtures where one liquid is spread throughout another. An everyday example of this is milk. Milk is an emulsion where fat droplets are distributed within a continuous phase of water. In emulsions like milk, hemulsifiers are often added to help stabilize the mixture, preventing the liquids from separating.

Even though both substances in these mixtures are liquids, they can't dissolve into each other fully, leading to a stable in-place suspension of small droplets. In some cases, shaking or stirring the mixture can help disperse the particles more evenly.

Dispersion of Solid in Liquid

This type of dispersion occurs when solid particles are dispersed in a liquid. A common everyday example is paint. Paint consists of pigment particles that are finely distributed throughout a liquid solution to create a uniform color when applied to a surface.

Fine grinding of the pigment ensures that the particles are small and even, allowing for smoother application and a more consistent appearance. These dispersions need to remain stable over time, so they often include thickeners to prevent the pigments from settling.

Dispersion of Gas in Solid

In the case of dispersions involving gas in a solid, the most illustrative example is pumice stone. Pumice is a porous, volcanic rock that forms when volcanic eruptions trap gas bubbles within solidifying lava.

This results in a light, sponge-like material characterized by small cavities or "vesicles." Despite its solid state, pumice is filled with these gas pockets, significantly reducing its density and allowing it to float on water.

Dispersion of Liquid in Solid

When liquid is dispersed in a solid, it forms a structure where liquid droplets are trapped within a solid matrix. Butter is a perfect example. During the butter-making process, fat droplets are dispersed within a semi-solid structured phase.

As the butter cools, these droplets remain trapped, giving butter its unique texture and consistency. Understanding the dispersion concepts in butter further helps in appreciating the chemistry behind many everyday food items and their diverse textures and behaviors.