To measure a volume of a liquid, you can pour it into a measuring cylinder. Measuring cylinders come in different shapes and sizes- tall, short, wide, narrow. Explain why the shape of the cylinder does not affect the measurement of the volume.

In the figure given, what is happening to ice at point $C$?

Name the substance or substances present in the section marked $D$.

From the figure, deduce the melting point octadecanoic acid.

The below table shows melting point and boiling points of nitrogen and oxygen, the main constituents of air. Why can we not talk about the melting and boiling points of air?