Why is a thermometer dipped in a liquid before use and why is the thermometer plced under the tongue?

A thermometer is dipped in a liquid before use to ensure that it is calibrated correctly and to avoid any residual temperature from previous measurements. Placing the thermometer under the tongue allows for accurate measurement of body temperature, as this area provides a consistent and stable environment that reflects core body temperature. Additionally, the sublingual region is easily accessible and minimizes the risk of external factors affecting the reading.