A colloid is a heterogeneous system in which one substance is dispersed as very fine particles in another substance. Their range of diameters is between 1-1000 nm. Based on dispersed phase and dispersion medium, colloids may be of different types like sol, gel, emulsion, aerosol, foam etc. Based on nature of interaction between two phases, sols are divided into Lyophillic and Lyophobic sols. Colloidal solutions exhibit various properties like Tyndall effect, Brownian movement and Electrophoresis. Stability of colloids is due to presence of charge. If somehow charge is removed, the particles will coagulate. Coagulation rate by various solutions containing ions, is decided by Hardy-Schulze rule. Everyday we come across many colloids. The meals we eat, clothes we wear, wooden furniture etc. are largely composed of colloids.

Match List I with List II

Choose the correct answer from the options given below:

A-IV, B-III, C-II, D-I

The correct answer is option 4.  A-IV, B-III, C-II, D-I.

Let us match each item in List I with the correct item in List II and provide a detailed explanation for each:

A. Aerosol

An aerosol is a colloidal system in which very fine particles or droplets of a liquid or solid are dispersed in a gas. The particles are typically in the range of 1 nanometer to 1 micrometer.

Example: Mist is a classic example of an aerosol. It consists of tiny water droplets suspended in air. Other examples of aerosols include smoke and fog.

B. Gel

A gel is a colloidal system where a liquid is dispersed in a solid. Gels have a semi-solid consistency and are often used in a variety of applications such as in food products and personal care items.

Example: Butter can be considered a gel-like substance because it has a semi-solid consistency where fat is dispersed in a small amount of water and other components. Although it's not a perfect gel, it fits within the broader definition.

C. Emulsion

An emulsion is a type of colloidal system where two immiscible liquids are mixed, with one liquid dispersed in the other. Emulsions are often stabilized by emulsifiers.

Example:Cheese can be considered an emulsion because it involves fat droplets dispersed in a protein matrix. Although it's not a liquid emulsion, the concept of dispersion applies here as the fats are emulsified in the cheese.

D. Foam

A foam is a colloidal system where gas bubbles are dispersed in a liquid or solid. Foams are often formed by trapping air or gas in a liquid or solid matrix.

Example: Soap lather is a classic example of foam. It consists of air bubbles trapped in a liquid soap solution. This makes it an example of foam due to the dispersion of gas in a liquid.

So the correct option is: 4. A-IV, B-III, C-II, D-I