An easy to use Charles’ Law apparatus comprising a capillary tube which is sealed at the bottom and is calibrated with millimetre markings and a thermometer, both of which are clipped to a base board. The unit has a hole at the top for hanging onto a retort stand. In use the apparatus is suspended in a tall form beaker filled with water. The level of the bead and the temperature are noted and then the water is heated. Taking measurements every minute will allow the plotting of a graph of volume against temperature, at constant pressure (AP) showing the relationship between them. Extrapolation of the graph leads to a value of the absolute zero of temperature.