Match List I with List II.
List I
(A) Cheese
(B) Pumice stone
(C) Hair cream
(D) Cloud
List II
I. Di

Q: Why is cheese considered a liquid in solid and not solid in liquid?

In cheese, the continuous network that gives it shape is solid (proteins and fats), while water/moisture is trapped in small pockets within this network. Hence, it's a liquid dispersed in a solid.

Q: What is the difference between a gel and a solid sol?

A gel is a liquid dispersed in a solid (like jelly or cheese), whereas a solid sol typically refers to a solid dispersed in a solid (like colored glass) or gas in solid (like pumice).

Q: Are all creams emulsions?

Yes, most cosmetic creams, including hair cream, are emulsions, which are mixtures of two immiscible liquids like oil and water, stabilized by an emulsifying agent.

Q: Why is a cloud not a gas in gas mixture?

Gases always mix completely to form true solutions, not colloids. A cloud consists of condensed liquid water droplets suspended in the gaseous atmosphere.

Q: How can I easily remember these colloidal systems?

Relate them to their physical appearance. If it feels solid but has moisture, it's liquid in solid. If it's a liquid mixture of oil and water, it's an emulsion. If it floats in the air, it's an aerosol.

Question

Match List I with List II.

\begin{array}{ll}
	ext{List I} & 	ext{List II} \
	ext{(A) Cheese} & 	ext{I. Dispersion of liquid in liquid} \
	ext{(B) Pumice stone} & 	ext{II. Dispersion of liquid in gas} \
	ext{(C) Hair cream} & 	ext{III. Dispersion of gas in solid} \
	ext{(D) Cloud} & 	ext{IV. Dispersion of liquid in solid}
\end{array}

Choose the most appropriate answer from the options given below.

Options:

(A) A $ightarrow$ IV, B $ightarrow$ III, C $ightarrow$ II, D $ightarrow$ I

(B) A $ightarrow$ IV, B $ightarrow$ I, C $ightarrow$ III, D $ightarrow$ II

(C) A $ightarrow$ III, B $ightarrow$ IV, C $ightarrow$ I, D $ightarrow$ II

(D) A $ightarrow$ IV, B $ightarrow$ III, C $ightarrow$ I, D $ightarrow$ II

Sigma Percentile · Accepted Answer

### The World of Colloids

Have you ever wondered what makes milk white, how clouds float in the sky, or why cheese has that unique texture? The answer lies in a fascinating realm of physical chemistry known as **colloids**. A colloidal system is a heterogeneous mixture where one substance is microscopically dispersed throughout another substance.

Unlike true solutions where the solute completely dissolves (like salt in water), or suspensions where particles eventually settle down (like sand in water), colloids hit the sweet spot. The particles are larger than individual molecules but small enough that they don't settle out under gravity.

Every colloid consists of two fundamental components:
1. **Dispersed Phase:** This is the substance that is distributed or scattered. You can think of it as the "solute" in a true solution.
2. **Dispersion Medium:** This is the continuous phase in which the dispersed phase is distributed. It acts much like the "solvent."

By mixing different states of matter—solid, liquid, and gas—we can create a wide variety of colloidal systems. Let's decode some everyday examples given in our problem!

### Decoding the Everyday Colloids

**1. Cheese: A Delicious Gel**
When you bite into a block of cheese, you might notice it feels solid but has a certain moisture or greasiness to it. This is because cheese is a type of colloid called a **gel**. In a gel, a liquid is dispersed throughout a solid network. During the cheese-making process, milk proteins coagulate to form a solid matrix, trapping liquid water and fats inside. Therefore, for cheese, the dispersed phase is **liquid**, and the dispersion medium is **solid**.

**2. Pumice Stone: A Volcanic Foam**
Pumice is a fascinating rock. It is so light that it can actually float on water! How is a rock so light? Pumice is formed during explosive volcanic eruptions when lava is ejected and cools rapidly. As it cools, the dissolved gases in the lava expand and get trapped in the solidifying rock, creating millions of tiny pores. This makes pumice a **solid foam** or solid sol. The dispersed phase is **gas**, and the dispersion medium is **solid**.

**3. Hair Cream: A Smooth Emulsion**
Cosmetic creams, including hair creams, lotions, and moisturizers, are classic examples of **emulsions**. An emulsion is a special type of colloid where both the dispersed phase and the dispersion medium are liquids that normally wouldn't mix—like oil and water. By using an emulsifying agent, tiny droplets of oil are stabilized in water (or vice versa). Thus, for hair cream, the dispersed phase is **liquid**, and the dispersion medium is also **liquid**.

**4. Cloud: Floating Water Droplets**
When you look up at a fluffy white cloud, you are looking at a massive colloidal system! A cloud is not water vapor (which is an invisible gas); rather, it consists of condensed, microscopic liquid water droplets suspended in the atmosphere. This type of colloid is known as an **aerosol**—specifically, a liquid aerosol. Here, the dispersed phase is **liquid**, and the dispersion medium is **gas** (the air).

### The Final Match

Now that we have analyzed the physical chemistry behind each of these everyday items, let's align them with our given lists:

*   **(A) Cheese** corresponds to **IV. Dispersion of liquid in solid**.
*   **(B) Pumice stone** corresponds to **III. Dispersion of gas in solid**.
*   **(C) Hair cream** corresponds to **I. Dispersion of liquid in liquid**.
*   **(D) Cloud** corresponds to **II. Dispersion of liquid in gas**.

Putting it all together, the correct matching sequence is **A $\rightarrow$ IV, B $\rightarrow$ III, C $\rightarrow$ I, D $\rightarrow$ II**.

This perfectly matches option (d). It is truly remarkable how the abstract concepts of surface chemistry govern the physical properties of the world around us, from the food we eat to the sky above us!

Select Answer:

Visualized Solution

$Understanding Colloids$

$Analyzing Cheese$

$Analyzing Pumice Stone$

$Analyzing Hair Cream$

$Analyzing Cloud$

$Final Conclusion$

The Sigma Insight: Colloids, Micelles and and Emulsions

The World of Colloids

Decoding the Everyday Colloids

The Final Match

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