Understanding the Change of State: Solid to Gas

The question asks to identify the specific change of state where a substance moves directly from the solid state to the gaseous state without passing through the intermediate liquid state. This process is a fundamental concept in chemistry and physics related to the properties of matter.

Identifying the Correct Process: Sublimation

Let's examine the given options and their definitions:

• Sublimation: This is the physical process where a substance changes directly from the solid to the gas state, without passing through the liquid state. An example is dry ice (solid carbon dioxide) changing directly into gaseous carbon dioxide at room temperature and pressure.
• Evaporation: This is the process where a substance in a liquid state changes to a gaseous state due to an increase in temperature and/or pressure. It typically occurs below the boiling point.
• Deposition: This is the reverse process of sublimation. It is the change of state from gas directly to solid, without passing through the liquid state. An example is frost forming from water vapor on a cold surface.
• Boiling: This is the process where a liquid changes into a gas when it is heated to its boiling point. Unlike evaporation, boiling occurs throughout the bulk of the liquid.

Comparing the definition from the question with the definitions of the options, it is clear that Sublimation is the process that describes the change of solid state directly to gaseous state without going through liquid state.

Therefore, based on the definitions of the states of matter and their transitions, the change of solid state directly to gaseous state is known as sublimation.

Why Other Options Are Incorrect

• Evaporation and Boiling involve a transition from the liquid state to the gaseous state, not solid to gas.
• Deposition is the transition from gas to solid, the reverse of what the question describes.

Revision Table: Understanding Phase Transitions

Additional Information on Sublimation

Sublimation occurs when a substance has a sufficiently high vapor pressure even in its solid state. This allows solid particles to escape directly into the gaseous phase. Not all substances sublime easily; it depends on the substance's triple point on its phase diagram. The triple point is the temperature and pressure at which the three phases (solid, liquid, and gas) of a substance coexist in thermodynamic equilibrium.

For sublimation to occur, the pressure must be below the triple point pressure, or the temperature and pressure conditions must be such that the direct solid-gas transition is energetically favorable compared to solid-liquid-gas transitions.

Examples of substances that sublime:

• Dry ice (solid \(\text{CO}_2\))
• Iodine
• Naphthalene (mothballs)
• Arsenic
• Camphor