Question

Which among the following metals is liquid at room temperature ?

• A. Mercury
• B. Iron
• C. Copper
• D. Alluminium

Hint:

Only one metal has a melting point below room temperature. It was used in old thermometers.

Answer 1

The Correct Option is A

Step 1: Think of melting points:
A substance is liquid at room temperature only if its melting point is below room temperature and its boiling point is above it.

Step 2: List the values:
Iron: 1538. Copper: 1085. Aluminium: 660. Mercury: minus 39. All in degrees Celsius.

Step 3: Compare with 25 degrees Celsius:
Only mercury has a melting point below 25. The other three are far above it, so they are solid.

Step 4: Real use:
This is why mercury was used in old thermometers. It stays liquid and expands evenly when heated.

Final Answer:
Only mercury is liquid at room temperature, so option 1 is correct. \[ \boxed{\text{1 (Mercury)}} \]