Physics
Physics
Problem
A mercury thermometer has the ice point (0 °C) and the steam point (100 °C) marked 10.0 cm apart on its stem. When its bulb is placed in an unknown liquid, the mercury column rises 2.5 cm above the ice point. (i) Calculate the temperature of the liquid in °C. (ii) Name the principle that justifies using the thermometer reading as the liquid’s temperature.Intuitive explanation
A thermometer works by assuming the mercury's expansion is linear with temperature—the distance the liquid rises is directly proportional to how many degrees have passed. Since you know the full 100 °C span corresponds to 10.0 cm, you can set up a simple ratio to find what temperature matches a 2.5 cm rise. This is thermal equilibrium in action: the mercury reaches the same temperature as the liquid it's measuring.
Intuitive explanation
A thermometer works by assuming the mercury's expansion is linear with temperature—the distance the liquid rises is directly proportional to how many degrees have passed. Since you know the full 100 °C span corresponds to 10.0 cm, you can set up a simple ratio to find what temperature matches a 2.5 cm rise. This is thermal equilibrium in action: the mercury reaches the same temperature as the liquid it's measuring.