HOW THERMOMETER WORKS ??
A Bulb thermometer has a glass tube sealed at both ends and is partly filled with a liquid like mercury or alcohol. The glass tube is mounted on a backboard that is marked in units called degrees. When it is hot, the liquid inside the thermometer will expand and rise in the tube. The opposite happens when it is cold. Numbers are placed alongside the glass tube that mark the temperature when the line is at that point.