It consists of mercury as a liquid filled in a glass tube. On the body of the glass tube, calibrated marks are provided which facilitates the reading of temperature. A bulb is formed at one end of the thermometer which contains the largest part of mercury.
Keeping this in consideration, what is the physical property of liquid-in-glass thermometer?
A thermometer has a liquid in a very narrow tube, which when heated will expand and move up the tube. If you cool the liquid down, then the liquid will contract and move back down the tube. So the physical property used in a thermometer is thermal expansion.
Moreover, why are liquids used in a thermometer?
It is because the liquids like mercury and alcohol expand uniformly on increasing temperature and also contracts uniformly on decreasing the temperature. So, it gives us the accurate measure of the temperature. That’s why liquids are used in the thermometer not solids or gases.