Understanding Water Cycle Processes: Solid to Vapor

The water cycle involves the continuous movement of water on, above, and below the surface of the Earth. Water changes states between liquid, solid (ice), and gas (vapor) throughout this cycle. The question asks about a specific process where snow and ice, which are forms of solid water, directly convert into water vapor without first melting into liquid water.

Identifying the Correct Process: Sublimation Explained

Let's examine the options provided to determine which process describes the direct conversion of solid water (snow or ice) into water vapor:

• Evaporation: This is the process where liquid water turns into water vapor. It happens from the surface of bodies of water, soil, and even within organisms. This is a liquid-to-gas transition, not solid-to-gas.
• Sublimation: This is the process where a substance transitions directly from the solid to the gas state, skipping the liquid state. In the water cycle, sublimation occurs when snow and ice turn directly into water vapor. This process is significant in cold, dry, and windy conditions, such as in mountainous regions or polar areas.
• Boiling: This is a rapid form of evaporation that occurs at a specific temperature (the boiling point) throughout the bulk of the liquid, not just at the surface. It involves the transition from liquid to gas.
• Transpiration: This is the process where plants release water vapor into the atmosphere through tiny pores on their leaves called stomata. This is also a process involving the release of water vapor, but it originates from liquid water within plants.

Based on the definitions, the process where snow and ice (solid) get directly converted into vapours (gas) is sublimation. This is a key part of the water cycle, particularly in environments where temperatures may not rise above freezing, but the energy from the sun or wind is sufficient to drive the solid-to-gas conversion.

Therefore, the process described, where snow and ice are directly converted into vapours in the water cycle, is sublimation.