If heat is released from water vapor, what phase change occurs?
A) liquid to gas
B) solid to gas
C) liquid to solid
D) gas to liquid
The Correct Answer and Explanation is:
The correct answer is D) gas to liquid.
This phase change is known as condensation. Condensation occurs when a gas, in this case, water vapor, loses heat and transitions into a liquid. The process of condensation is the opposite of vaporization, where a liquid absorbs heat and changes into a gas.
Here’s a more detailed explanation:
Water vapor, in the gaseous phase, consists of water molecules that are in a high-energy state, moving rapidly and widely separated from one another. As heat is released (for example, when steam cools), the energy of the water vapor molecules decreases. As the molecules lose kinetic energy, they begin to slow down, and their attraction to one another increases. This leads to the molecules coming closer together and forming liquid water again, which is the process of condensation.
Condensation is commonly observed when warm, moist air comes into contact with a cool surface, such as the formation of droplets of water on the outside of a cold glass of water. Another example is the formation of clouds in the atmosphere, where water vapor condenses into tiny liquid water droplets when cooled to a certain temperature. The temperature at which condensation occurs is known as the dew point.
To summarize, when heat is released from water vapor, the phase change that occurs is from gas to liquid (condensation). This is a process where the water molecules slow down as they lose energy, causing them to transition from the vapor state back to the liquid state. This phase change is crucial in many natural processes, including weather patterns, the water cycle, and everyday occurrences such as the formation of dew.