Temperature range suitability of common instruments Which instrument from the list can reliably measure temperatures from about −20 °C up to approximately 300 °C in routine practice?

Introduction / Context:
Selecting a temperature instrument requires matching the sensor’s useful range to the application. Many processes operate near ambient yet occasionally reach several hundred degrees Celsius. An understanding of the typical coverage of classic instruments helps avoid over-specification and ensures dependable readings.

Given Data / Assumptions:

• Target span is roughly −20 °C to 300 °C.
• Instruments listed: mercury-in-glass, vapor-pressure thermometer, and resistance thermometer (RTD).
• We assume standard, commonly available industrial or lab-grade devices.

Concept / Approach:
Mercury-in-glass thermometers commonly cover from about −39 °C to roughly 357 °C (boiling point of mercury), with many commercial scales spanning −20 to 300 °C comfortably. Vapor-pressure thermometers have ranges that depend on the fill fluid; some ranges may not simultaneously cover −20 to 300 °C without changing bulbs/fills. RTDs can indeed cover this span, but the question aims at a single, conventional instrument “from the list” that is routinely available pre-scaled for −20 to 300 °C—this is very typical for mercury-in-glass devices.

Step-by-Step Solution:

Verification / Alternative check:
Supplier catalogs show many mercury thermometers directly spanning −20 to 300 °C with appropriate capillary and scale design.

Why Other Options Are Wrong:

• Vapor pressure thermometer: Range depends on fill; a single instrument may not span −20 to 300 °C.
• Resistance thermometer: Technically capable, but the question context favors a traditional, self-contained thermometer; the mercury device is the canonical match.
• None of these: Incorrect because mercury-in-glass fits well.

Common Pitfalls:
Confusing “can be designed to measure” with “commonly supplied in a single off-the-shelf range.”

Final Answer:
Mercury in glass thermometer