Problem 22 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Smoke is an example of :(a) Solid dispersed in solid(b) Gas dispersed in liquid (c) Solid dispersed in gas (d) Gas dispersed in solid

Step-by-Step Solution

Answer

Smoke is an example of solid dispersed in gas, option (c).

Step 1: Understand the Components of Smoke

Smoke consists of tiny particles of solid material, such as unburned carbon and ash, dispersed in a gas. To answer the question, it's essential to identify the type of mixture that smoke represents.

Step 2: Determine the Dispersed Phase and the Dispersing Medium

In smoke, the solid particles (like carbon) are the dispersed phase, while gases in the air (such as nitrogen, oxygen) act as the dispersing medium.

Step 3: Analyze the Options

Given the definition from Step 2, smoke is a system where a solid is dispersed in a gas. Hence, (c) Solid dispersed in gas matches this description best.

Step 4: Select the Correct Answer

Based on the analysis, the correct answer for the dispersal type represented by smoke is (c) Solid dispersed in gas.

Key Concepts

Colloids

Colloids are a fascinating state of matter, representing a unique type of mixture where one substance is dispersed evenly throughout another. Unlike solutions, where the dissolved substance completely dissolves and becomes invisible, colloids have larger dispersed particles. These particles, although larger than molecules, remain small enough to not settle out quickly or be filtered easily. This gives colloids their characteristic cloudy appearance.

There are several types of colloids, depending on the states of matter involved. A few common examples include:

• Foams: Gas particles in a liquid or solid, like whipped cream or foam rubber.
• Aerosols: Liquid or solid particles in a gas, such as fog or smoke.
• Emulsions: Liquid particles in a liquid, such as oil in water.

The persistent dispersion of particles is what keeps colloids stable and fascinating for scientific study. They play an important role in many aspects of everyday life, from the food we eat to the atmospheric phenomena we observe.

Mixtures

Mixtures are composed of two or more substances that are combined physically, meaning there is no chemical reaction between them. They can be separated by physical means such as filtration, evaporation, or decanting.

Mixtures come in varying forms, including:

• Homogeneous Mixtures: These are uniform in composition, such as salt dissolved in water, which forms a clear solution.
• Heterogeneous Mixtures: These contain visibly different substances or phases, like a salad or trail mix.

Colloids, including smoke, fall under heterogeneous mixtures. The solid particles are distributed within the gas, making the disparity clear under magnification. The key feature of mixtures is that each component retains its own properties, allowing us to tailor them for specific needs. This flexibility is what makes mixtures integral to many industries and processes.

Dispersion Phase

In colloids and mixtures, the concept of dispersion phases plays a crucial role. The term 'dispersed phase' refers to the particles that are distributed throughout another substance, known as the 'dispersing medium'.

This classification is essential because it determines the behavior and classification of the colloid:

• Dispersed Phase: The phase of the smaller, distributed particles. In smoke, this is the solid particles like carbon.
• Dispersing Medium: The substance in which the dispersed phase is distributed. For smoke, this is the air or gas.

Understanding these phases helps to identify and differentiate between various types of colloids and mixtures. For example, fog is a colloid where water droplets (dispersed phase) are distributed in air (dispersing medium). Recognizing these components aids in the scientific analysis and practical application of mixtures, such as in pollution control or food preparation.