Question

Candle wax and petrol both produce the same gases on heating. Why is petrol a better fuel than wax

Answer 1

Because petrol helps in complete combustion. So less pollution arise.

while wax being an unsaturated compounds burns with sooty flame.

Answer 2

petrol converts into gas faster than wax does

as petrol has to become from liquid to gas and it is a one step process

but

wax has to convert from c\solid to liquid to gas this is a two step process

thus petrol is a better fuel than wax