Here's a breakdown:

* Solid to Liquid: This is called melting.

* Liquid to Gas: This is called boiling or evaporation.

* Solid to Gas: This is called sublimation.

Sublimation happens when a solid substance absorbs enough energy to directly transition into a gas phase, skipping the liquid phase altogether. This happens because the molecules in the solid have enough energy to break free from the solid structure and escape into the gaseous phase.

Examples of sublimation:

* Dry ice (solid carbon dioxide) sublimates at room temperature. This is why it's used for special effects like fog and smoke.

* Snow and ice can sublimate in cold, dry conditions. This is why snowdrifts can shrink even when the temperature is below freezing.

* Mothballs (naphthalene) slowly sublimate over time, releasing a vapor that repels moths.

* Frozen water can sublimate in a vacuum, which is how freeze-drying works.

Let me know if you have any more questions!