Which instrument must not be heated?

• A. Volumetric Pipet
• B. Graduated Cylinder
• C. Thermometer
• D. Funnel

Answer: (A)

Volumetric pipets are calibrated to deliver a precise volume at a specific temperature, usually around 20°C. Heating one changes both the glass and the liquid inside, so the actual delivered volume no longer matches the marked value. That loss of calibration is exactly why this instrument must not be heated when you need a precise amount. Other glassware like a graduated cylinder or funnel isn’t held to that same tight, temperature-specific calibration, so they’re not considered unacceptable to heat in routine handling. A thermometer, on the other hand, is designed to respond to temperature changes; heating it isn’t about delivering a fixed volume and is part of how it functions to measure heat.