Question

The phase change from solid to vapour without passing through liquid phase occurs:

• A. Triple point of water
• B. Above the triple point of water
• C. Any temperature and pressure combination
• D. Below the triple point of water

Hint:

Sublimation: solid \(\rightarrow\) vapor directly.
Occurs below the triple point.
Examples: dry ice (CO\(_2\)) sublimates at atmospheric pressure.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Phase change from solid to vapor directly is called sublimation.
It occurs under specific conditions.

Step 2: Key Formula or Approach:
No specific formula.
Need to know the phase diagram of water.

Step 3: Detailed Explanation:
Sublimation occurs when the pressure is below the triple point.
The triple point is the temperature and pressure where solid, liquid, and vapor coexist.
For water, the triple point is at 0.01°C and 611 Pa.
Below this pressure, solid water (ice) directly changes to vapor.
Thus, sublimation occurs below the triple point.

Step 4: Final Answer:
Phase change from solid to vapor occurs below the triple point of water.
Hence, the correct option is (D).