11. Andrew made a hand-made gas thermometer. The length { of a gas column in a uniform capillary tube varies with temperature T. He uses a set-up as shown to calibrate his thermometer. thermometer ruler stirrer capillary tube liquid thread trapped - water bath gas column Part of the results during the calibration is as shown. T / C 22 97 4 / mm 64 80 (a) Before taking each reading, what should he do to ensure that the gas column reaches the same temperature as the water bath? (2 marks) (b) Assume { increases linearly with T throughout. (i) Estimate the temperature indicated by the gas thermometer when f is 76 mm. (2 marks) (ii) Length { cannot be negative, so there should be a lowest possible temperature To (call it absolute zero). Find To from the data obtained. (2 marks)