Question

Give Reason: Icebox has double walls.

Answer 1

Hint: We all know that to get a feasible heat transfer from one medium to another medium, we need a parameter which is a physical property called conductivity, and if there is good conductivity, then the heat transfer will take place.


Complete step by step answer:
In solids, the conductivity of heat takes place by lattice vibrations of the solid crystals. In conductors, it's easy to excite the lattice crystals, but in insulators, the lattice needs much more energy for the molecules to get excited.
We must keep in mind that conductivity also depends on the thickness of the conductors. If the thickness of the conductor will increase the thermal resistance to heat will also increase, and hence it will obstruct the diffusion of heat.
In the case of the icebox, it is fabricated with dual iron plates, and in the middle of the plates, there is glass wool which is generally a very bad propagator of heat. If the heat will try to propagate through the plates, it will have to face very high thermal resistance, and since heat transfer also depends upon a time so, the ice would take a considerable amount of time to melt inside.


Note: We must keep in mind that out of the most and best of the best insulators, we have polyurethane foam. The conductivity of this foam is least among all the insulators. After it, we have air which is known as the bad conductor of heat and electricity. Glass wool is also known for its good insulating properties.