What is Sublimation? What are its principles, process and examples?

Solid, liquid, and gas are typical phases for most substances. Every substance has its own physical and chemical properties with its boiling and melting point. To change a solid substance into two other types, it needs energy in form of heat, called an endothermic reaction. So, an endothermic reaction in sublimation changes a solid phase into the gaseous phase. During the phase transition, a solid directly converts into a gas without any intermediate state (liquid). It occurs when atmospheric pressure is too low. When the temperature and pressure of a substance are below to triple point of the substance, sublimation happens. It's a physical reaction rather than a chemical one. For Ex, Burning wood is not an example of sublimation because combustion occurs due to reactant oxidization, but sublimation needs energy as input.

The word sublimation is derived from the Latin word "sublimate", which means "to raise", used since the late 1550s. "Jabir Ibn Hayyan (Gerber)" was the first who explain this process in the 700s. Dry Ice was discovered by him and he is known as the "father of chemistry".

Principle of sublimation:

Basically, In this, the absorption of heat process takes place, and due to it, molecules get excited and try to escape from weak attractive forces of other molecules. Depending on temperature and pressure, these escaped molecules either melt or become gas. So, you can define sublimation as the process when a solid becomes gas.

Sublimation: List of Examples

We usually see the sublimation process around us but neglect it. Let's discuss examples in two categories: 1- examples of sublimation from industries, 2- examples of sublimation from daily life.

Examples of sublimation from industries:

• Dry Ice:Dry Ice is the best example of sublimation. It's a frozen form of carbon-di-oxide; when exposed to air, changes into gas directly can be seen with the naked eye as fog. The gaseous form is more stable than the solid state, it is also mentioned in class 11 chemistry books.
• Corrosive gas sublimationis a degrading procedure in alchemical activities where metallic vapors like mercuric chloride are sublimated inversely.
• Polar evaporation:Part of water sublimes into the atmosphere as water is frozen below 0⁰C at the terrestrial poles.
• Iodine and arsenic change from solid to gas at high temperatures.
• As gases in supernovas sublimate inversely, solid matter in planets happens.
• Sulfur powder, widely used in industries, is obtained through it.
• Aluminum can be sublimated at a temperature greater than 1000⁰C under particular pressure.

Examples of sublimation from daily life:

• Air fresheners:You all are familiar with air fresheners used in your cars and washrooms. It comes as solid and sublimes into a gas state. The particles bring a pleasant smell.
• Ice and Snow:During weather seasons, you can see sublimation of Ice or Snow around you.
• Ice crystals:Ice crystals formed on frozen food are caused due to sublimation process of frozen foods.
• Purification of metals:When certain metals, especially alloys, can be purified using the sublimation process. In this process, they get heated under controlled conditions to change into a gaseous state, resulting in purification.
• Naphthalene mothballs:To protect clothes or fibers from moth, we use naphthalene balls that come in the form of solid and turns into the gaseous state to keep them away.

Requisitions of Sublimation:

We see things around us based on sublimation and, yes, valuable to us. For instance, you can take any example like air fresheners, naphthalene mothballs, or camphor. You feel the sublimation effect visibly. So let's make a note of some of the sublimation applications. Although you have studied these in Class 10 science.

• Sublimation is helpful in forensic science. Iodine sublimation is used to expose forensic evidence on paper.
• Chemists use it as a purification method to purify volatile compounds. Sublimation is very useful for organic compounds.
• The textile industry uses dye sublimation printing techniques to print synthetic materials like polyester.
• We can make flags, T-shirts, and banners using the dye sublimation printing method.
• Bags, pens, and coffee mugs can be printed using the dye technique at a reduced cost.
• Sublimation is used to store food for an extended period of time. Maintaining the quality of food in orbit is a challenge for astronauts. NASA and ISRO space agencies use this method to supply high-quality meals to them.
• One of the popular applications of sublimation is in the frozen food industry. As surrounding pressure reduces, water freezes on food sublimates.
• There is no trash left in this process. Hence, this process is safe and environmentally friendly.
• With this technology, we can get scratch-proof images, wash-resistant, and many decorative works.
• Sublimation is used to manufacture signs, name badges, and full-color plaques.

Uses of sublimation:

• Lyophilization is the process of freezing a solution like tea, soup, or drugs and heating them from medium to high vacuum at a slow rate. The freeze-dried substances are created using this method.
• The cool finger is a process used by chemists to purify compounds. When heated, a vacuum is released, and you can collect the sublimed mixture from the cooled surface.
• The sublimation process is accelerated when arid air circulation combines with sub-zero temperature. That's why the shelves and walls of the freezer remain free of Ice.
• Dye sublimation is a process used to color print on paper and various other substrates. Solid dye material is heated using small heaters, and then that material gets deposited on the paper. We can obtain good-quality pictures even with low resolution. Transfer toner is used to print on plain paper in standard black and white color. These toners contain sublimation dyes.
• Deep-Etch is a technique in which liquid nitrogen is used to freeze the tissue samples and then transferred to the sublimed surface of the vacuum device. In this way, the 3D structure of hydrated material is preserved.

As we know, when any phase changes, there is always energy associated with it. In sublimation, heat is provided to change from a solid to a gas state. The solid that is transforming into gas is sublime. When vapors get cooled, the solid particles formed are called sublimate, and the sublimation process only applies when complete physical change occurs in the state. A solid directly sublimes into gas, and both the temperature and pressure of that solid should be below the triple point. Snow, iodine, arsenic, dry Ice, etc., are the solids that normally sublimate at normal temperature and pressure. You are free to ask if you want to learn more about the Sublimation class 9^th topic, we will solve your doubts. We provide online tuition classes for Class 9 Science and Class 12 chemistry. The syllabus is designed in an easy and interactive way to help you by our experienced tutors.