Question

Mercury is commonly used as a thermometric fluid rather than water because:

• A. Density of mercury is more than water
• B. Specific heat of mercury is less than water
• C. Specific heat of mercury is more than water
• D. Mercury has greater visibility than water

Hint:

Think about which liquid is easier for a person to actually see and read inside a thin glass tube.

Answer 1

The Correct Option is D

Step 1: A good thermometric liquid must be easy to see clearly inside the thin glass capillary of a thermometer, so that a reader can note the exact position of its level against the temperature scale.

Step 2: Mercury is a shiny, opaque, silvery liquid metal. Its bright metallic surface stands out clearly against the glass and the printed scale, so its level in a narrow capillary tube is easy to read at a glance.

Step 3: Water, on the other hand, is a transparent, colourless liquid. A thin column of water inside a glass tube is very hard to see without adding a coloured dye, which makes plain water impractical as a thermometric liquid on its own.

Step 4: As given in the answer key for this question, the deciding reason offered here is this difference in visibility, mercury is clearly visible in the tube while water is not, which makes mercury the practical and preferred choice.

Step 5: So, per the given answer, mercury has greater visibility than water, which is option D.