 #1
yamata1
 61
 1
 Homework Statement:

A bloc of ice at temperature 273 K and height h has a plate of surface S with symetrically distributed weights of mass M hanging on both sides, so constant pressure is applied to the bloc and begins melting,the water rises from under the plate and refreezes above the plate.
What is the entropy change ##dS_1## of a mass dm of ice melting?
What is the entropy change ##dS_2## of a mass dm of water refreezing?
In using the fact that ##\Delta T << T_0##, deduce therefrom the rate of change of total entropy; what is its sign (comment)?
Show that the total variation of entropy during the complete process where the plate has passed through the ice is independent of ##L_f## and is worth ##∆S=\frac{2Mgh(v_lv_s)}{V_g T_0}##
Let ##P1 = P_0 + ∆P## and ##T_1 = T_0 + ∆T## be the equilibrium pressure and temperature of the ice under the plate. We denote by ##L_f## the specific latent heat of fusion of the ice, ##v_l## and ##v_s ## the volumes mass of liquid water and ice, g acceleration of gravity. We will assume that variations in temperature and equilibrium pressure on either side of the plate are weak enough that ##L_f##,##v_l## and ##v_s## can be considered constant, their values being those of the state (##T_0, P_0##).
 Relevant Equations:

##L_f=\frac{Q}{m} \; \; ##,##∆T=\frac{T(v_lv_s)∆P}
{L}## I dont know how to express the total entropy change.
Thank you for help
##dmL_f= Q \; \; ##,##∆T=\frac{T(v_lv_s)∆P}{L} \; \;##,##\frac{dmL_f}{T_0}= dS_2 \; \;##,##\frac{dmL_f}{T_1}= dS_1 ##