Question

Describe an experiment to demonstrate that a substance absorbs heat during melting without change in its temperature.

Answer 1

To demonstrate that a substance absorbs heat during melting without change in its temperature

MELTING POINT OF SOLID (WAX):

Put some wax in a test tube. Insert a thermometer in solid wax, so that bulb of thermometer remains in wax and does not touch the sides.

Clamp the test tube along with thermometer in hot bath i.e. in the water contained in the beaker and set up the apparatus. Note the temperature.

Heat the beaker over the flame of the burner and record the temperature after every minute. The temperature rises and then reaches 68°C and wax shines in the test tube.

The temperature remains constant for nearly 5 minutes i.e. at 68°C. This means Wax is melting and the temperature remains constant till the whole of the wax is melted. Then the temperature rises again every minute.

Conclusion: The temperature remains constant at 68°C while changing from solid to liquid. This means 55°C is the melting point and heat is absorbed without a change in temperature. This heat is absorbed at constant temperature till the whole of wax is melted.