Which instrument is used to measure temperature in a scientific context?

The instrument used to measure temperature in a scientific context is the thermometer. Thermometers operate based on the principle that certain materials expand or change properties with temperature. In many cases, a liquid like mercury or colored alcohol is contained within a sealed glass tube. As the temperature increases, the liquid expands and rises within the tube, providing a clear visual indication of the temperature on a calibrated scale.

Other instruments listed have different primary functions. For example, a volumetric pipet is used to measure and transfer precise volumes of liquids, which is crucial in quantitative analysis but not related to temperature measurement. A stirring rod serves to mix solutions together or facilitate the mixing of substances, while a centrifuge is designed to separate components of a mixture based on density through the application of centrifugal force. None of these alternatives are designed for measuring temperature, making the thermometer the correct choice for that specific task.