Question

Describe an experiment to show that there is absorption of heat energy when the ice melts.

Answer 1

Experiment to show that there is absorption of heat energy when ice melts:
1) Take a boiling test tube and fill it half with the ice chips. Insert a thermometer gently into the ice taking care that its bulbs does not touch the walls of test tube. Note the temperature of ice. It will be 0oC.
2) Heat the test tube slowly over the flame and note the temperature after every half minute till the temperature of water formed after melting of ice increases to 30oC.
Plot a graph between temperature and time. This graph is called heating curve of ice. From the graph, it is clear that the temperature of ice remains constant equal to 0oC in the AB part till the whole ice is melted. The heat supplied during this time is being used in melting the ice. After this, the temperature of water formed by melting the ice begins to rise in the part BC. Thus, change of phase occurs in part AB and heat energy is absorbed during this time without any rise in temperature.