Question

A cylinder containing gas is closed by movable piston. The cylinder is submerged in an ice-water mixture. The piston is quickly pushed down from position 1 to position 2. The piston is held at position 2 until the gas is again at $0^{o}C$ and then slowly raised back to position 1. Represent the whole process on P-V diagram. If m = 100gm of ice are melted during the cycle, how much work is done on the gas. Latent heat of ice = 80cal/gm

Answer 1

as the piston is moved the air molecules gets energized due to kinetic energy and as they come into contact with the container walls some of that energy gets transferred to the mixture and hence temperature of mixture goes up and ice starts to melt.

A specific latent heat $\left(L\right)$ expresses the amount of energy in the form of heat $\left(Q\right)$ required to completely effect a phase change of a unit of mass (m), usually 1kg, of a substance

$L=\frac{Q}{m}=>Q=mL$

Enegy required to melt 100 gm ice $Q=80\times 100=8000cal$