Task: Determination of the Temperature of Cooling Wax.
Required Accessories: 1 test tube, 1 beaker, 1 stand, some wax, water, 1 thermometer, spirit lamp, wire-net, tripod and clamp.
Procedure: Take some wax in the test tube. Fill up the three fourth portion of the beaker by water. Keeping the wire-net over the tripod place the beaker upon it Immerse the test tube in the water of the beaker as shown m the figure. Continue to apply heat on the bottom of the beaker by spirit lamp till the as completely melts down. Now immerse the thermometer in the test tube so that the lower part of it remains dipped m the melting wax. Remove the test tube with thermometer from the beaker then hold it by the clamp m the stand. Clean the test tube by tissue paper. Observe the temperature of the thermometer. See the temperature at the moment when the wax begins to freeze.
Analysis: At what temperature does wax begins to freeze? Is It 57 degree Celsius? Yes, that is correct. This temperature that is 57 degree Celsius is the freezing point of wax. Earlier you got the melting point of wax as 57 degree Celsius. That means the melting point and freezing point of a matter are same.
We know the freezing point of water is Zero degree Celsius. Then the melting point of water (in the form of ice) should also be zero degree Celsius.
If the temperature of a matter remains beyond its freezing point and if it is greater than the surrounding temperature, then if the matter is kept in the surrounding temperature, it losses heat slowly. As a result, its temperature decreases and when the temperature comes to the freezing point. It changes to solid state, as it happened in case of wax. When the wax was in liquid state, its temperature was more than 57 degree Celsius. When the test tube with wax was brought out side it emitted heat slowly. As a result, the temperature decreased. It was decreasing in this way to reach the freezing point e.g. 57 degree Celsius, and then the wax got frozen to become solid.