Question

paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not

Answer 1

Paper by itself catches fire easily because it attains its ignition temperature .Hence burns.

Whereas,
 A paper wrapped in aluminum pipe does not burn because:
---> Aluminum is a metal and a good conductor of heat.
--->Heat energy supplied is absorbed by aluminum pipe. 
--> Paper never attains its ignition temperature.
--> Hence paper wrapped in aluminium pipe does not burn.

Answer 2

Answer:

Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not. The ignition temperature of paper is less, so it catches fire easily. It does not catch fire when wrapped around aluminium pipe because aluminium absorbs the heat, so paper does not attain its ignition temperature.