What is the process of changing the state of matter called?

The latent heat of vaporization of a substance is....

The graph signifies:

Two substances $A$ and $B$ of equal mass $m$ are heated at a uniform rate of $6 \, cal \, s^{-1}$ under similar conditions. $A$ graph between temperature and time is shown in the figure. The ratio of heat absorbed $H_A/H_B$ by them for complete fusion is

$A$ block of ice at $-10\,^oC$ is slowly heated and converted to steam at $100\,^oC.$ Which of the following curves represents the phenomenon qualitatively?

Compared to a burn due to water at $100\,^{\circ}C$,a burn due to steam at $100\,^{\circ}C$ is: