Which of the following propeties is not considered in choosing mercury as a thermomemetric liquid?

Analyze the question: We need the property that is NOT a reason for choosing mercury as a thermometric liquid.

Concept: Mercury is used in thermometers because of these properties:

• Expansivity (B): It expands uniformly and regularly with temperature, so the scale is even and easy to read.
• Conductivity (C): It is a good conductor of heat, so it quickly reaches thermal equilibrium with the body being measured.
• Opacity (D): It is opaque and shiny, so the thread is easy to see in the glass tube.
• Other reasons: it does not wet glass, has a wide liquid range (−39 °C to 357 °C), and has a low specific heat capacity.

Density (A): Mercury is very dense (13,600 kg/m³), but density is not a property that makes it suitable for use as a thermometric liquid. Its use does not depend on how heavy it is. The properties that matter are those that affect how it responds to temperature changes and how visible it is.

Checking the options:

• A. Density: not a deciding factor ✔ (this is the answer)
• B. Expansivity: considered
• C. Conductivity: considered
• D. Opacity: considered

Answer: A (density)

Exam tip: Remember the key reasons for mercury as "E-C-O-N": Expands uniformly, Conducts heat well, Opaque, and Not wetting the glass. Density is not on the list, so it is the odd one out.