* Calorific value means energy released in burning of 1 gram of fuel.* Ignition temp.. means substance that catches fire easily.
Calorific value: The heating value or calorific value of a substance, usually a fuel or food, is the amount of heat released during the combustion of a specified amount of it. The calorific value is a characteristic for each substance. It is measured in units of energy per unit of the substance, usually mass, such as: kcal/kg, kJ/kg, J/mol, Btu/m³.Ignition temperature\tThe lowest temperature at which a substance catches fire and undergoes combustion liberating heat and light is called ignition temperature.\tIn other words it is the minimum temperature at which a combustible substance such as air or gas, must be heated up prior to burning in the absence of any source of the heat. This temperature plays a key role in determining the safety criterions for low volatile products such as diesel oil, lubricating oil, and fuel oil.\tWe have already observed that matchstick gets ignited as soon as we strike it against the matchbox whereas it takes a lot of time to ignite a mosquito repellent.
The minimum temperature at which subistance start burning is called ignity temperature. And the burning efficiency of subsistence is cslled calorfiy value