Calibration curve of a thermometer using a mercury thermometer as a standard

An unmarked thermometer (alcohol in this expt.) can be calibrated using a mercury thermometer as a standard. Both thermometers are placed in melting ice (0 degrees C), the length of the alcohol "thread" is noted. A heater is switched on causing the water temperature to gradually increase. For at least six temperature values the corresponding length of the alcohol thread is noted. A graph of length of alcohol thread against temperature is the required calibration curve.

Procedure:

  1. Familiarise yourself with the scale on the thermometer and on the ruler. Note the starting temperature and the length of the alcohol thread. Record in a table as shown below.
  2. Press " Apply Heat".
  3. As the temperature increases note the temperature and the corresponding length of the alcohol in the unmarked thermometer at least six times
  4. The hotplate stops automatically when the temp. reaches 100 degrees Celcius. If you want to repeat the experiment press "Reset" and repeat steps 2 and 3
Temperature (deg.C)
Length of alcohol thread (cm)
   

Analysis:

Plot a graph, on graph paper, of length of alcohol thread (y-axis) against temperature. Any temperature between 0 and 100 degrees can now be measured using the unmarked thermometer. Place it in a beaker of moderately hot water, measure the length of the alcohol thread and, from the calibration curve, read the corresponding temperature.

Precautions:

  • Place both thermometers in melting ice (0 deg. C) for a few minutes at the start of the experiment.
  • Heat the water very slowly so that it is easy to take temperature and length readings simultaneously
  • Have your eye level with the liquid columns when taking temperature and length readings to avoid parallax errors