Structured Qns...

1. (a) In a household refrigerator, the freezer compartment is placed at the top. Explain why this is so.
(b) When the refrigerator door is opened for a short time, the cold air inside is replaced by the warmer air outside. Why does this exchange of air have little effect on the temperature of the contents in the part of the refrigerator below the freezer compartment ?
(c) Explain why the cooling fins at the back of the refrigerator is black.

2. (a) Explain why a household electric kettle has a polished surface.
(b) What is the reason for placing the heating element at the bottom of the kettle?
(c) Most kettles have plastic handles. Why?

3. A solar panel is used to heat water.
(a) State the name of the process by which energy is transferred
(i) from the Sun to the outside of the pipe in the solar panel.
(ii) from the outside of the pipe to the water inside it.
(b) (i) Which of the following materials would be the most suitable for the pipe that contains the water
a. black plastic
b. white plastic
c. glass
d. black-painted copper
e. polished steel
(ii) Give two reasons for your choice of material.

4. Explain the following observations.
(a) Birds usually fluff up their feathers during cold weather
(b) Excessive sunbathing can cause skin cancer