Question

The process of change of liquid state into gaseous state at constant temperature is known as:

• A. boiling
• B. melting
• C. fusion
• D. evaporation

Hint:

textbfEvaporation occurs at all temperatures, but textbfboiling occurs only at a fixed temperature (boiling point).

Answer 1

The Correct Option is A

Step 1: Recall the definitions of phase changes.

Boiling: Change of liquid into gas at a fixed (constant) temperature called the boiling point.
Evaporation: Change of liquid into gas at any temperature, occurring only at the surface.
Melting/Fusion: Change of solid into liquid.
Step 2: Analyze the given condition. The question clearly states that the change occurs at a constant temperature. Step 3: Identify the correct process. Only boiling occurs at a constant temperature. Step 4: Final conclusion. The correct answer is \(\boxed{\text{(A) boiling}}\).