Brief Notes on Sublimation

Sublimation is the process by which a substance changes directly from the solid to the gas state without passing through the liquid state. When a substance’s triple point in its phase diagram is reached, which corresponds to the lowest pressure at which the substance can exist as a liquid, sublimation happens as an endothermic process. In contrast to sublimation, deposition, also known as de-sublimation, is the process by which a substance passes directly from the gaseous to the solid phase. As a generic term, sublimation can be defined as the process of going from a solid to a gas, followed by a gas to solid transition (sublimation), and so forth (deposition). The transition from liquid to gas occurs as evaporation from the surface of the liquid if it occurs below the boiling point of the liquid, and as boiling with formation of bubbles in the liquid if it occurs at the boiling point of the liquid, but there is no such distinction for the transition from solid to gas, which occurs as sublimation from the surface of the solid regardless of the temperature at which it occurs.

A physical change of state is denoted by the term “sublimation,” which is not used to describe the transformation of a solid into a gas in a chemical reaction, as is the case with “sublimation.” A chemical reaction, such as the dissociation of solid ammonium chloride into hydrogen chloride and ammonia upon heating, is not a sublimation but rather a chemical reaction. Additionally, the burning of candles with paraffin wax to produce CO2 and water vapour is not a sublimation, but a chemical reaction involving the presence of oxygen.

Sublimation is caused by the absorption of heat, which provides enough energy for some molecules to overcome the attractive forces of their neighbours and escape into the vapour phase. Sublimation occurs when heat is absorbed, which causes some molecules to escape into the vapour phase. Because the process necessitates the use of additional energy, it is classified as an endothermic change. The enthalpy of sublimation (also known as the heat of sublimation) can be calculated by adding the enthalpy of fusion and the enthalpy of vaporisation together in a single equation.

Example of sublimation:

Carbon dioxide: 

At pressures and temperatures above the triple point, solid carbon dioxide (dry ice) sublimes everywhere along the line below the triple point (for example, at a temperature of 78.5 degrees Celsius (194.65 degrees Kelvin, 109.30 degrees Fahrenheit) at atmospheric pressure), whereas its melting into liquid CO2 can occur anywhere along the solid-liquid line at pressures and temperatures below the triple point (for example, at 5.1 atmospheres and 56.6 degrees Celsius).

Naphthalene:

Sodium naphthalene, a non-polar organic compound that is commonly found in pesticides such as mothballs, sublimes easily because it is composed of non-polar molecules that are held together only by van der Waals intermolecular forces, which are weak in nature. Naphthalene is a solid that sublimes at standard atmospheric temperature, with the sublimation point being approximately 80 degrees Celsius or 176 degrees Fahrenheit. Its vapour pressure is high enough at low temperatures, 1 mmHg at 53 °C, for example, to cause the solid form of naphthalene to evaporate and become a gas. The naphthalene vapours will solidify into needle-like crystals if they come into contact with cool surfaces.

Purification by sublimation:

Chemists use sublimation to purify compounds, which is a technique known as vaporisation. Typically, a solid is placed in a sublimation apparatus and heated under vacuum until it melts. In response to the reduced pressure, the solid volatilizes and condenses as a purified compound when it comes into contact with a cooled surface (cold finger), leaving a non-volatile residue of impurities behind. The purified compound can be collected from the cooling surface after the heating process has finished and the vacuum has been removed. A temperature gradient is used to achieve even higher purification efficiencies while also allowing for the separation of different fractions.

Dye-sublimation printing:

Dye-sub printing is a digital printing technology that prints full-colour artwork on polyester and polymer-coated substrates. It is also known as sublimation printing. As digital sublimation, the path of process is commonly used for decorating apparel, signs, and banners, as well as novelty items such as cell phone covers, etc, coffee mugs. and other items with sublimation-friendly surfaces, among other things. Heat and pressure are applied to a solid, causing it to turn into a gas through an endothermic reaction without passing through the liquid phase. This is accomplished through the science of sublimation.

Conclusion:

In chemistry, sublimation is defined as the transition of a substance from its solid state to its gas state without passing through the liquid phase in between.Sublimation is the process by which a substance changes directly from the solid to the gas state without passing through the liquid state.

Sublimation is caused by the absorption of heat, which provides enough energy for some molecules to overcome the attractive forces of their neighbours and escape into the vapour phase.Naphthalene is a solid that sublimes at standard atmospheric temperature, with the sublimation point being approximately 80 degrees Celsius or 176 degrees Fahrenheit.

Chemists use sublimation to purify compounds, which is a technique known as vaporisation. Typically, a solid is placed in a sublimation apparatus and heated under vacuum until it melts.

Dye-sub printing is a digital printing technology that prints full-colour artwork on polyester and polymer-coated substrates. It is also known as sublimation printing.