The thermometer whose thermometric property is change in volume with temperature is

1. Analyze the question

The question asks us to identify a specific type of thermometer based on its "thermometric property." A thermometric property is any physical property of a substance that changes predictably with temperature. We are looking for a thermometer that specifically relies on the change in volume of a substance as the temperature changes.

2. Explain the concept

Different thermometers use different physical properties to measure temperature:

• Resistance thermometer: Uses the change in electrical resistance of a metal wire (usually platinum) as temperature changes.
• Thermocouple: Uses the change in electromotive force (e.m.f.) generated at the junction of two dissimilar metals due to a temperature difference (Seebeck effect).
• Bimetallic thermometer: Uses the differential expansion of two different metals bonded together, which causes the strip to bend as temperature changes.
• Liquid-in-glass thermometer: Uses the thermal expansion of a liquid (like mercury or alcohol). As the temperature rises, the liquid expands, increasing its volume and causing it to rise up the capillary tube.

3. Show the solution

• Step 1: Evaluate Option A. Resistance thermometers measure electrical resistance, not volume.
• Step 2: Evaluate Option B. Thermocouples measure voltage (e.m.f.), not volume.
• Step 3: Evaluate Option C. Bimetallic thermometers measure mechanical bending (deformation) caused by expansion, not the volume change of a liquid.
• Step 4: Evaluate Option D. In a liquid-in-glass thermometer, the liquid (mercury or alcohol) is contained in a bulb. When heated, the liquid expands (its volume increases), forcing it to move into the narrow stem. This direct relationship between volume change and temperature is the fundamental principle of this device.

4. Identify the answer

The correct option is D.

5. Exam Tip

To remember this easily, think of the "liquid" inside the glass tube. Liquids are known for their expansion when heated. If you see "volume" in a question about thermometers, always look for the option involving a liquid (mercury or alcohol).