Charles Law - Irwin [3296]

Irwin Charles Law. A clear simple way of demonstrating that the volume of a fixed mass of gas is proportional to its absolute temperature. It comprises a Jolly's apparatus on an anodised stand. A scale is marked in mm. Spring clips secure an air reservoir and adjustment is made using a vertical clamping rod. Comes complete with a leveling tube and Jolly air thermometer. Supplied with oil. Thermometer -10 - 100°C. Height 33.5cm x width 40cm x depth 1.5cm. 

Instructions:

Fill a 400ml beaker with water, sit it on a tripod/gauze and then immerse the Charles’ Law Apparatus into the water so that the water level is about the 10mm position on the scale. It is advisable to hang the apparatus from a clamp rod mounted on a retort stand. A suitable hole is provided for this. Take a temperature reading and a scale reading from the bottom of the bead in the capillary bore. Heat the water using a Bunsen burner and take both readings every 30s. Plot a graph of length (volume) against temperature. Plot a line of best fit. You should get a straight line which intersects the volume axis. If you rescale the graph so that the temperature axis goes down to about - 300oC, you should be able to extrapolate the absolute zero of temperature. 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.

N.B. Before carrying out the experiment ensure that the base of the capillary tube is aligned with the zero mark on the base plate. If there is a small amount of oil at the base of the tube align the top of the oil mark to the zero mark.

The Irwin Charles’ Law Apparatus comprises a capillary tube, which is sealed at the bottom, showing a scale from 0 to 200mm. This is mounted onto a backing plate which also has a -10 to 100oC thermometer mounted alongside the tube. Due to movement of the oil in the capillary tube in transit separation of the bead may occur, therefore we supply the oil separately in a small container along with a Syringe which allows the customer to fill it.

Video Presentation available on the IPC Irwin website: http://www.ipcirwin.com/charles-law-apparatus

Contents of the Kit:
1 x Charles Law Apparatus as shown.
1 x Bottle of biodegradable oil.
1 x 1ml Syringe.
1 x 0.8 x 120mm Hypodermic Needle.
Filling the capillary Tube:
1. Carefully remove the needle from its case, keep the case for storage when the needle is not in use.
2. Fit the hypodermic needle to the syringe. NOTE:
• Please use extreme care when handling needles.
• These needles are for non-medical purposes and can be reused.
• Ensure the needle is stored safely making sure no accidental needle stick injuries can occur when storing or retrieving it for future use.
• Make sure the needle is not accessible to unauthorised personnel or students.
• When disposing of the needle, please conform to all guidelines for the disposal of hypodermic syringes in a properly marked bin.
3. Remove the top from the bottle of oil and draw a small amount of oil into the syringe. NOTE: The oil is olive oil and can be disposed of by pouring it down the sink with a little washing-up liquid.
4. Run the syringe with the oil in it under a hot tap or place in a beaker of warm water to increase the fluidity of the oil.
5. Carefully, place the needle into the capillary tube and slowly press the plunger to express the oil into the tube.
6. The bead of oil should be approximately 1cm in length 

Additional Information:
Should the bead of oil become separated into two or more beads through shaking, it means that a gap of air has been allowed to divide the bead. This can be overcome by removing the capillary tube from the holder and placing it into a beaker filled with warm water. Allow the capillary tube to lean at an angle simply by resting it on the side of the beaker. The heat reduces the viscosity of the oil and allows the air to escape, this normally takes between 10 to 20 minutes depending on the temperature of the water.
NOTE: Do not use boiling water as this reduces the viscosity too much and the bead will disintegrate.