TRANSMISSION OF HEAT

1) conduction

the heat travels through the molecule of substance without movement of molecule themselves.(molecule doesn't travel.)

2) convection :

            when the fluid (liquid and gas) heated the expands so the heated molecules become lighter and moves upward and cold molecules takes place . this process continues.

3) radiation:

            In this way heat travels without any medium. it does not heat the medium approximately. heat travels in a straight line.

e g: heat from sun comes without any medium (zero atmosphere) to the earth by radiation.

FLASH POINT, FIRE POINT, IGNITION TEMP.

FLASH POINT:    

                           The min temp at which the rate of vaporization of fuel is sufficient to produce a momentary flash upon the application of source of ignition.

FIRE POINT:  

                         The min temp at which the burning vapor is capable to enable combustion to continue.

IGNITION TEMP:   

                                   The min temp at which fuel will ignite without help of ignition source. it also called "auto ignition temp"

SOURCE OF IGNITION

a) spark:

            * friction

            * static charge

            * loose electric connection

            * lightening

            * welding

b) flame

            * match stick

            * gas cutting torch

c) heat of chemical reaction

            *exothermic reaction

d) heat of compression

e) nuclear heat