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

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

When vapour condenses into liquid,

Two substances $A$ and $B$ of equal mass are heated at a constant rate of $6 \ cal \ s^{-1}$. The graph shows the temperature versus time. What is the ratio of the heat absorbed for complete melting $H_A/H_B$?

Two different liquids of the same mass are kept in two identical vessels, which are placed in a freezer that extracts heat from them at the same rate, causing each liquid to transform into a solid. The schematic figure below shows the temperature $T$ versus time $t$ plot for the two materials. We denote the specific heat in the liquid states as $C_{L 1}$ and $C_{L 2}$ for materials $1$ and $2$, respectively, and the latent heats of fusion as $L_1$ and $L_2$, respectively. Choose the correct option.

$Assertion :$ Melting of a solid causes no change in internal energy.
$Reason :$ Latent heat is the heat required to melt a unit mass of a solid.