Ans... for the Stuctured Qns....

1. (a) The freezer compartment is placed at the top because cold air, being denser, will sink to the bottom while hot air will rise to take its place, and is turned to cold air on top and again the cold air will sink, setting up a convection current.
(b) As hotter air from outside moves in, it will quickly rose up, to the freezer compartment being less dense than the cold air inside the refrigerator due to convection current. Thus, the hot air will not have enough time to warm up the contents below the freezer compartment.
(c) The cooling fin of the refrigerator is painted black because black is a better emitter of heat and it radiates heat readily.

2. (a) It is because polished surfaces are bad emitter of heat energy and thus it will prevent heat loss from the kettle to the surroundings.
(b) This is because of convection current. As hot water rises, cold water will sink to take its place and thus it is heated up by the heating element at the bottom.
(c) This is because plastic are a bad conductor, thus it prevents the user from getting scalded.

3. (a)(i) Radiation
(ii) Conduction
(b)(i) d.Black-painted copper
(ii) This is because copper is a good conductor of heat and therefore will quickly transfer the heat to the water. Secondly, black surfaces is a better absorbers of heat rather than white, polished surfaces.

4. (a) When birds fluff up their wings, it is trapping air, and as air is a bad conductor of heat, the heat from its body would not be lost to the surroundings cold air.
(b) This is due to the over-exposure of radiation from the sun, and the radiation will make the skin cells act abnormally.