Understanding the Conversion of Water Vapour to Water

The question asks about the specific scientific term used when water vapour, which is the gaseous state of water, changes back into liquid water. This process is a fundamental concept in the study of matter and its states.

Defining the Phase Change: Water Vapour to Water

Matter can exist in different states, such as solid, liquid, and gas. Changing from one state to another is called a phase transition or phase change. The conversion of water vapour (gas) back to water (liquid) is a common phase change we observe in everyday life, such as dew forming on grass or fog appearing.

Analyzing the Options

Let's look at the given options and determine which one correctly describes the process of water vapour turning back into liquid water:

• Evaporation: This is the process where liquid water changes into water vapour (gas). This is the opposite of what the question is asking.
• Freezing: This is the process where liquid water changes into solid ice. This involves changing from liquid to solid, not gas to liquid.
• Condensation: This is the process where a substance in its gaseous state changes into its liquid state. Specifically, for water, this is the process where water vapour changes into liquid water. This matches the description in the question.
• Sublimation: This is the process where a solid substance changes directly into a gas, bypassing the liquid state. A related process, deposition, is when a gas changes directly into a solid. Neither describes gas turning into a liquid.

Identifying the Correct Term: Condensation

Based on the definitions of the options, the term that refers to the conversion of water vapour back to water is Condensation.

Condensation occurs when water vapour cools down or when the concentration of water vapour in the air becomes too high (reaches saturation point), causing the water molecules to lose energy and come closer together, forming liquid water droplets.

Example of Condensation:

• When you see your breath on a cold day.
• Water droplets forming on the outside of a cold glass.
• Clouds forming in the sky (water vapour in the air condenses into tiny liquid water droplets).

Revision Table: Key Concepts in Water Phase Changes

Additional Information: The Water Cycle and Condensation

Condensation is a crucial part of the Earth's water cycle. After evaporation turns liquid water into water vapour, this vapour rises into the atmosphere. As the water vapour cools at higher altitudes, it undergoes condensation, forming clouds made of tiny liquid water droplets or ice crystals. When these droplets or crystals become heavy enough, they fall back to Earth as precipitation (rain, snow, hail, etc.), completing a cycle.

Understanding phase changes like condensation is important in meteorology, chemistry, and many environmental sciences.