The given graph shows the heating curve for a pure substance. The temperature rises with time as the substance is heated : (a) What is the physical state of the substance at the points A, B, C and D ? What is the melting point of the substance ? (c ) What is its boiling point ? (d) What happens to the temperature while the substance is changing state ? (e ) The substance is not water. How can you judge from the graph ?

The given graph shows the heating curve for a pure substance. The temp

1.	The given graph shows the heating curve for a pure substance. The temperature rises with time as the substance is heated : (a) What is the physical state of the substance at the points A, B, C and D ? What is the melting point of the substance ? (c ) What is its boiling point ? (d) What happens to the temperature while the substance is changing state ? (e ) The substance is not water. How can you judge from the graph ?
Answer» Solution :(a) At point A : The substance is in the solid state. At point B : The substance has started melting. It exists both in the solid and liquid states. At point C : The substance is in the liquid state. A point D : The substance has started boiling. It exists both in the liquid and gaseous states. (b) the melting point of the substance is `15^(@)C`. (c ) The boilingpoint of the substance is `110^(@)C`. (d) The TEMPERATURE REMAINS the same during the change of state. (e ) Had substance been water, its melting point should have been `0^(@)C` and boiling point `100^(@)C`. It is therefore, not water.