Question

Draw a neat diagram of temperature versus time when a substance is heated from $0^{o}C$ to ${80}^{o}C$. Along with this, also draw another curve when the molten substance cools to room temperature. How will you find the melting and freezing point from the graphs drawn?

Answer 1

Temperature versus time diagram

Graph of temperature(T) versus time(t) of substance when it is heated from $0^{o}C$ to ${80}^{o}C$ and when the molten substance cools to room temperature:

1. In the above graph, curve AB represents the heating of substance from $0^{o}C$ to ${80}^{o}C$.
2. Curve BC represents the melting of the substance to liquid.
3. In the curve CD, the liquid is converted to solid.

From the above graph:

1. Melting point is calculated by drawing a horizontal line to the curve BC. “M” represents the melting point.
2. Freezing point is calculated by drawing a horizontal line to point D. “N” represents the freezing point.