Question

Nando performs experiments mixing ice at −5 ◦C and water at 40 ◦C. If you put a certain mass of ice and a certain mass of water, you notice that the final temperature is 0 ◦C and all the ice melts; If you now increase the mass of ice you used in the previous experiment by two kilograms (keeping the temperatures the same) and use the same mass of water, the final temperature is still 0 ◦C, but now all the water is frozen. Determine the two mass values ​​that Nando used in the first experiment

Answer 1

When two substance at different temperature are mixed together then exchange of heat take place till temperature of both tge substance become equal.This temperature is called as final temperature of the mixture ir equilibrium temperature.

Heat given by one substance = Heat taken by another substance

m1 *s1*∆T1= m2 * s2* ∆ T2

∆T1 =273 - 268 = 5K

∆T2 = 313 - 273 = 40 K

m1 = mass of ice in gram.

m2 = mass of water in gram.

Si= specific heat of ice = 1/2 cal/gm°C

Sw =specific heat of water = 1 cal/gm°C

Lf = latent heat of fusion= 80 cal/gm

Latent heat is the heat supplied to substance during phase change of solid to liquid and liquid to solid.

Case i has m1 x Lf on left hand side because ice is changing to water phase is changing while in case second water is changing in ice again phase is changing but this time m2 x Lf on right hand side.