Sublimation

Sublimation is the process in which a substance directly changes from a solid to a gaseous state without passing through the liquid phase. This change occurs when the substance is heated to a temperature at which its vapor pressure exceeds the atmospheric pressure. Sublimation is an endothermic process, meaning that it requires energy in the form of heat to occur.

Examples of Sublimation:
1. Dry ice - When dry ice, which is solid carbon dioxide, is heated it directly changes into carbon dioxide gas without melting into a liquid.
2. Camphor - When camphor is heated, it directly changes into a gaseous state without melting.
3. Naphthalene balls - Naphthalene balls used for moth control also undergo sublimation on heating.

Uses of Sublimation:
1. Sublimation is used in the purification of substances. For example, when impure solid iodine is heated, it directly changes into iodine vapor, which can be collected and condensed into pure solid iodine.
2. Sublimation is used in the production of certain chemicals, such as in the production of semiconductor materials.
3. Sublimation is also used in the manufacturing of dry ice, which is used in refrigeration and transportation of food and medical products.

Conclusion:
Sublimation is a process in which a substance directly changes from a solid to a gaseous state without passing through the liquid phase. It is an important process with various industrial and scientific applications.