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In nature, substances have different states or phases: solid, liquid, and gas. A phase transition is when a substance changes from one of these states to another. Sublimation is a special type of phase transition where a solid changes directly into a gas.
Unlike melting or boiling, sublimation skips the liquid phase entirely. Common examples of sublimation include dry ice, which is solid carbon dioxide, turning into gas at room temperature. This happens because the molecules in the solid gain enough energy to break free into a gaseous state.
Phase transitions are important because they explain how matter interacts with energy and changes shape depending on the conditions. Understanding phase transitions helps us control processes in everyday life, like refrigeration and cooking.

Every phase transition needs a certain amount of energy to occur. So, when you think of sublimation, think of it as an energy-involving process.
To change from solid to gas, molecules must gain extra energy to break the bonds holding them tightly in the solid. In sublimation, this energy is supplied as heat. This means that we need to heat the substance for sublimation to take place.
Heat energy increases the movement of molecules, supplying the necessary push to overcome intermolecular forces. As heat is added, molecules start moving faster until they have enough energy to escape into the gas phase. The energy input for sublimation is crucial as it dictates how efficiently a substance can transform from solid to gas without first becoming a liquid.

Intermolecular forces are the invisible glue that holds matter together in its solid or liquid state. These forces include attractions like hydrogen bonds, van der Waals forces, and ionic bonds. These forces are key players in determining the energy required for a phase transition.
In solids, these forces are strong, keeping the particles closely packed. During sublimation, the energy input is used to overcome these forces.
Simply put, the heat provided during sublimation is used to break these bonds, freeing the individual molecules into a gaseous state. Understanding these forces helps us comprehend why some substances require more energy than others to sublimate. Depending on the strength of the forces, the sublimation temperature can be high or low. Therefore, substance behavior during phase changes significantly depends on the nature and strength of these intermolecular forces.