K.C.S.E Physics Q & A - MODEL 2009PP1QN08

K.C.S.E Physics Q & A - MODEL 2009PP1QN08

Two identical empty metal containers P and Q are placed over identical Bunsen burners and the burners lit. P is dull black while Q is shiny bright. After each container attains a temperature of 100⁰C the burners are turned off. Identical test tubes containing water are suspended in each container without touching the sides as shown in figure 3

​Explain why the container Q may become hot faster than P. 
Explain why the water in test- tube in P becomes hot faster than in Q 

ANSWERS

• Dull surface radiate faster than bright surface
•  P- Looses more of the heat supplied by burner than Q OR
• Q shinny surface is a poorer radiator/ emitter of heat thus retains more heat absorbed Or
•  P- Dull surface is a better radiator/ emitter i.e. retains less of the heat absorbed. ( there must be a comparison between P & Q)
• Heat travels from container to test tube by radiation so the dull surface P, gives more heat to the test tube.