Understanding Water Vapour Conversion to Water

The question asks about the specific term used for the process where water vapour changes back into liquid water. This is a fundamental concept in the study of states of matter and phase changes.

Let's examine the given options to identify the correct term for the conversion of water vapour to water:

1. Condensation: Condensation is the process by which water in its gaseous state (water vapour) turns into liquid water. This happens when water vapour cools down, causing the water molecules to lose energy and slow down, allowing the attractive forces between them to pull them together to form liquid water. This process is commonly observed when steam hits a cold surface, or when clouds form in the atmosphere.
2. Evaporation: Evaporation is the opposite process of condensation. It is the process by which liquid water turns into water vapour (gas). This happens when water absorbs enough energy (usually heat) to overcome the attractive forces holding the molecules together in the liquid state, allowing them to escape into the air as a gas.
3. Freezing: Freezing is the process by which liquid water turns into a solid state, which is ice. This occurs when water is cooled to its freezing point (0°C or 32°F at standard atmospheric pressure), causing the water molecules to arrange themselves into a rigid, crystalline structure.
4. Sublimation: Sublimation is the process by which a substance changes directly from a solid to a gas state without passing through the liquid state. An example is dry ice (solid carbon dioxide) turning directly into carbon dioxide gas. The reverse process, where a gas turns directly into a solid, is called deposition or desublimation.

Comparing the question's requirement (conversion of water vapour back to water) with the definitions of the options, it is clear that condensation is the term specifically used for the change of water from the gaseous state (water vapour) to the liquid state (water).

Phase Changes of Water

Water can exist in three common states: solid (ice), liquid (water), and gas (water vapour). The conversion between these states are known as phase changes and are driven by changes in temperature and pressure. Here is a summary:

Based on the table and definitions, the conversion of water vapour (gas) back to water (liquid) is indeed called condensation.

Revision Table: Water Phase Changes

Additional Information: Real-World Examples of Condensation

Condensation is a very common process that we observe daily:

• Formation of dew on grass in the morning.
• Formation of fog and clouds in the atmosphere.
• Water droplets forming on the outside of a cold glass.
• Water vapour from breathing condensing on a cold window pane.
• Steam from cooking condensing on kitchen surfaces.

These examples illustrate the process of water vapour converting back into liquid water, which is defined as condensation.