1) When and why does a boiling range exists? 2) Why is water used for cooling the vapours of kerosene in the experiment for determination of boiling range of kerosene sample? 3) What is the difference between grease and lube oil? 4)Composition of Natural Gas changes with time in the same well-why? 5)Natural Gas and Liquified Petroleum Gas burners are not interchangable-why? 6)Can Natural Gas and Liquified Petroleum Gas be considered as green fuel? 7)What is steam tracing, what is the quality of steam used?why?