Charles' Law Mounted

Comprises a capillary tube, sealed at one end, with graduated scale from 0 to 200mm, mounted on a plastic former which also has a 0 – 70°C thermometer mounted alongside the tube.

The glass tube includes a small bead of coloured oil, which has already been injected into the tube at about the 50mm mark, and the back plate has a hole at the top to allow fixing to a retort stand, so that the apparatus can be suspended in a tall beaker of water (not included). By heating the water and taking a temperature and scale reading every 30 seconds, a graph of the results can be plotted. Through a line of best fit and extrapolation absolute zero can be demonstrated. The straight line supports Charles’ Law, demonstrating that volume of a gas is directly proportional to its temperature, provided the pressure is kept constant. (In this case the pressure is atmospheric pressure). The Kelvin scale may then be introduced.

Dimensions: Glass tube, 245mm long; Overall length, 350mm.

Available individually or as a class set of 10 in a Gratnells tray.

Replacement capillary tubes with oil beads are also available, sold as a pack of 10.

Q = Is the oil already in place in the tube or does it need to be injected?
A = Yes, the oil is already injected at around 12-13cm on the scale. It is a coloured oil such as chilli oil.

Q =  The coloured oil bead has become separated and there is an air bubble in the middle of the oil. How do I re-join the oil?

A = This can happen, as with thermometers, during transit or when the apparatus gets knocked or roughly handled. To re-join the oil bead, take some thin wire (e.g. nichrome, copper etc.) or nylon fishing line and push this into the bore of the tube, then move it up and down through the oil and bubble and it should get rid of the bubble so that the oil re-joins.

Q = What are the dimensions of the tube?

A = Tube dimensions are:
Length: 25cm
Outer diameter: 6mm
Inner diameter (bore): 2mm approx.