The tool designed to measure temperature is a thermometer. There are many types of thermometers, but the working principle is the same. Usually, we use thermometric objects, the nature of matter that changes with temperature. If the temperature of the object changes, the shape, and size of the object also changes. Most thermometers use objects that can expand or shrink when the temperature changes. Thermometers that are often used consist of glass tubes, where there is alcohol or mercury in the center of the tube. When the temperature increases, alcohol or mercury in the container expands so that the length of the alcohol or mercury column increases. Conversely, when the temperature decreases, the length of the alcohol or mercury column decreases. On the outside of the glass tube, there are numbers which are the scale of the thermometer. The number shown by the upper end of the alcohol or mercury column states the value of the temperature of the object being measured.