Condensation Methods

The transition of water vapour into liquid is known as condensation. Condensation can occur in two ways: the air is chilled to its dew point, or it becomes saturated with water vapour to the point where it can no longer retain its state. Condensation is a reaction in which two molecules combine, and water droplets are lost due to the response. It also entails the removal of heat from a mechanism that converts vapour to liquid. There are several condensation methods for the preparation of colloids, including changing the solvent, changing the physical state, using excess cooling, and using chemical procedures.

Meaning of condensation 

Transforming the state of matter from a gas to a liquid is called condensation. It is the opposite of evaporation. In other words, as the hot water vapour in the air came into touch with the cold mirror’s surface, it cooled. This led the water vapour to condense or change from a gas to a liquid. 

Different techniques create lyophilic and lyophobic colloidal solutions (or sols). By aggregating molecules or ions, condensation processes produce colloidal particles. If the particles grow more extensive beyond the colloidal size range, they form drops or precipitates, and there is no colloidal system. When water molecules aggregate and include colloid-sized particles, clouds form. If these water particles convert into sufficiently large liquid water droplets or solid water crystals, they fall as rain, sleet, or snow from the sky. Chemical processes are used in several condensation procedures. 

Condensation methods (aggregation methods)

The smaller particles of the dispersion phase are combined in condensation processes to generate bigger colloidal particles. These techniques are used to make solid/liquid dispersions or suspensions. There are three condensation processes: solvent exchange, physical state change, excessive cooling, and chemical approaches. The following are the details of each method:

1. By exchange of solvent

Because of its limited solubility in water, a sulphur or phosphorus solution in alcohol is poured into water to produce a colloidal sulphur or phosphorus solution. The actual material solutions are poured into another solvent in which the solute is insoluble, but the solvent is entirely miscible. Changing the solvent produces a colloidal solution of the solute.

2. By change of physical state

Certain elements, such as mercury and sulphur, can be made into colloidal solutions bypassing their vapour through cold water containing a stabiliser.

3. By a lot of cooling

A colloidal ice solution can be created by freezing a water solution in an organic solvent such as ether or chloroform. When water molecules can no longer be retained in solution, they mix to form particles of colloidal size.

4. Chemical methods

Some chemical processes can aggregate tiny particles of atomic or ionic sizes into larger colloidal particles. Some of the chemical methods are mentioned below:

(i) Double decomposition: A constant stream of hydrogen sulphide gas is run through a cold solution of arsenious oxide to form an arsenic sulphide sol in a double decomposition process. This is repeated until the yellow colour of the sol reaches its peak intensity.

As2O3    +   3 H2S  → As2S3(yellow)   +  3 H2O

A stream of hydrogen is used to eliminate any excess hydrogen sulphide

(ii) Oxidation: Passing oxygen through a hydrochloride solution produces a colloidal chlorine solution.

4HCL + O2  →2H2O + 2 Cl2

(iii) Reduction: By treating a dilute solution of silver nitrate or gold chloride with organic reducing agents such as tannic acid or formaldehyde, silver and gold sols can be made.

AgNO3 + tannic acid  → Ag Sol

AuNO3 + tannic acid →Au Sol

(iv) Hydrolysis: Hydrolysis of the salts of Fe, Cr, Al, and other hydroxides can be used to make colloidal solutions. Boiling a dilute ferric chloride solution yields a colloidal ferric hydroxide solution.

FeCl3 + 3H2O  →Fe(OH)3 (red sol) + 3HCl

Applications of condensation

• Condensation is a fundamental part of the distillation used in laboratory and industrial chemistry.

• In a cloud chamber, condensation is a critical step in generating particle tracks. In this situation, ions created by an impact particle act as nucleation centres, causing the vapour to condense and leave visible “cloud” trails.

• Condensation is used in commercial applications such as power production, water desalination, thermal management, refrigeration, and air conditioning.

Conclusion 

Condensation procedures include nucleation and growth and entail the “buildup” of molecular units. These techniques are used to make solid/liquid dispersions or suspensions. Various chemical approaches can be used to create hydrophilic or lyophobic colloidal solutions. The two most common ways to make a colloid are to reduce bigger particles to colloidal size and to condense smaller particles (such as molecules) into colloidal particles. Chemical processes, such as displacement, hydrolysis, or oxidation and reduction, are commonly used to condense smaller particles into a colloid.