What is Sublimation in Chemistry?

Sublimation is essential in chemistry and helps students understand various practical and theoretical applications related to this topic. Many real-life separation techniques, industrial processes, and even day-to-day phenomena are based on this concept.

What is Sublimation in Chemistry?

A sublimation process refers to the direct conversion of a substance from the solid state to the gaseous state, without passing through the liquid state. This concept appears in chapters related to states of matter, phase transitions, and physical and chemical changes, making it a foundational part of your chemistry syllabus.

Physical Principles of Sublimation

Sublimation occurs when the vapor pressure of a solid exceeds atmospheric pressure at a given temperature, allowing particles to escape directly into the air. The process usually requires heat, making it endothermic. Substances that can sublime include naphthalene, dry ice (solid CO₂), camphor, ammonium chloride, and iodine. These solids possess very weak intermolecular forces or special crystal structures, enabling this unique phase change.

Sublimation Process and Conditions

For sublimation to occur, specific conditions of temperature and pressure must be met. Everyday atmospheric pressure and a little heat are often enough for substances like camphor and mothballs. However, lower pressure or higher temperatures can enhance the process. The phenomenon is commonly explained using a phase diagram, which shows that sublimation happens below a substance’s triple point (where solid, liquid, and gas coexist).

State	Phase Change	Example
Solid to Liquid	Melting	Ice to water
Solid to Gas	Sublimation	Dry ice, naphthalene
Liquid to Gas	Evaporation	Boiling water

Examples of Sublimation

You will see sublimation both in laboratories and at home. Here are a few common examples for your understanding:

• Naphthalene balls kept in cupboards slowly disappear as they sublime into vapor, driving away insects.
• Dry ice or solid carbon dioxide, used for cooling and dramatic effects in parties or theatre, sublimates at room temperature to produce fog.
• Camphor, often used in worship, vanishes when left exposed to air due to sublimation.
• Iodine crystals, when heated, produce a violet vapor directly from the solid state.
• Ammonium chloride forms white fumes in labs by sublimation during heating.

Substance	Sublimation Seen in
Naphthalene	Repellent balls in wardrobes
Dry Ice (CO₂)	Fog machines at events
Camphor	Religious offerings, air fresheners
Iodine	Lab experiments, antiseptics

Applications of Sublimation

Sublimation is highly useful in real life and labs. Some major applications include:

• Purification: Used to separate volatile substances from non-volatile impurities, especially in separation techniques.
• Industrial Printing: The principle is used in dye sublimation printing on T-shirts, mugs, banners, and synthetic fabrics.
• Food Industry: Freeze-drying technique preserves food by sublimating frozen water directly into vapor, extending shelf-life.
• Medicines: Used in pharmaceutical processes for producing and storing sensitive vaccines and medicines.
• Air Fresheners: Sublimation ensures air freshener solids slowly vaporize into the room for a long-lasting fragrance.

Relation with Other Chemistry Concepts

Sublimation is closely related to evaporation, melting, and deposition (the reverse where gas turns directly to solid). It helps students bridge concepts between states of matter and energy changes, and is often connected to topics like endothermic reactions and phase diagrams.

Step-by-Step Sublimation Example

1. Place a mixture of common salt and ammonium chloride in a china dish.

2. Heat gently under an inverted funnel so ammonium chloride sublimes and the vapors collect as solid on the cooler funnel walls, leaving salt behind.

3. The collected solid is pure ammonium chloride, illustrating separation by sublimation.

Lab or Experimental Tips

Always use proper ventilation when heating substances like iodine or ammonium chloride, as their vapors can be harmful. Vedantu educators recommend using an inverted funnel and cotton plug to contain fumes and to prevent loss of material during sublimation experiments.

Try This Yourself

• Name two household substances that undergo sublimation.
• Draw a simple diagram or flowchart showing the solid-to-gas transition in sublimation.
• Is sublimation a physical or chemical change? Explain why.

Final Wrap-Up

We explored sublimation—its scientific basis, examples, and importance in daily life and the laboratory. Sublimation is a unique physical change connecting many chemistry topics, from states of matter to industrial printing. Visit Vedantu for live sessions and detailed notes on related topics to strengthen your chemistry basics.