Determine the Calorimeter Constant (W) of Calorimeter (Polythene Bottle)

In order to determine the calorimeter constant, a known volume of hot water at a known temperature is added to a known volume of water taken in the calorimeter at room temperature. Since energy is conserved, the heat gained by the calorimeter and the cold water must be equal to the heat lost by hot water. If t1  , t2 and t3  are the temperatures of cold water, hot water and mixture respectively and m1, m2 and m3   are the masses of calorimeter, cold water and hot water respectively, then we can write


  1. Put 100 ml of distilled water in polythene bottle with a thermometer and stirrer Fig.
  2. Note the temperature (t1 °C).
  3. Heat some water in a beaker to a temperature 20-30 °C higher than that of room temperature.
  4. Put 100 ml of this warm water in another beaker.
  5. Note the temperature of this water. Let it be t2 °C.
  6.  Add warm water from the beaker into the polythene bottle without any loss of time.
  7. Stir the contents.
  8. Read the temperature attained after mixing. Let it be t3 °C.

Volume of water taken in bottle = 100 ml
Temperature of water = t1 °C
Volume of warm water added = 100 ml
Temperature of warm water = t2 °C
Temperature after mixing = t3 °C

Heat given out by hot water = Heat taken by bottle and cold water.

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