Iplace a 500-g ice cube (initially at 0°c) in a styrofoam box with wall thickness 1.0 cm and total surface area 600 cm2 .

if the air surrounding the box is at 20°c and after 4 hours the ice is completely melted, what is the conductivity of the styrofoam material? (lf = 80 cal/g)
a. 9.6 × 10−5cal/s⋅cm⋅°c
b. 2.8 × 10−6cal/s⋅cm⋅°c
c. 1.15 × 10−2cal/s⋅cm⋅°c
d. 2.3 × 10−4cal/s⋅cm⋅°c

Para resolver este problema es necesario aplicar los conceptos relacionados a la conductividad térmica, para lo cual se tiene matematicamente que

Where,

K = thermal conductivity

A = Cross-sectional Area

= Change at temperature

x = Distance

= Difference of time

= Heat exchange energy

Our values are given as follow,

The total heat required to change the phase of ice would be

Where Lf Latent heat of fussion and m is the mass.

Replacing we would have:

Therefore the correct answer is D.

most of them using statistics and defining how things are being measured

freezing

deposition

condensation

explanation;

melting also called fusion is the process where solid becomes liquid, sublimation is the process where solid becomes gaseous without first changing to liquid, deposition involves change from gaseous to solid state, freezing involves change from liquid to solid, boiling or evaporation involves change of liquid to gaseous state, while condensation is the change from gaseous state to liquid state.

endothermic reactions involves absorption of heat from the surroundings or the environment while exothermic reactions involves loss of heat energy to the surroundings.

in this case, sublimation, evaporation and melting are endothermic reactions (gain energy from the environment) while, freezing, deposition and condensation are exothermic (loss of energy to the surroundings) reactions.