Slow combustion occurs when a substance burns over a longer period without any external heat. The fuel is exposed to air and creates slow reaction occurs between the particles in the fuel and oxygen which is in the air, producing no heat or light. Even though it burns slowly without external heat, the burning speed is different with every resource due to limited amount of oxygen reaching the combustible substance, hence smaller the surface area lowers the reaction speed.
The temperature in the place can have chance of rising until the ignition temperature has been reached for the fuel (every fuel has different temperature). When the max temperature has been reached the fuel burns itself spontaneously. This occurs during the heating of fuels like oil, kerosene or etc in stove and heating appliances.
There are sometimes when fuel and oxygen mixture is a type that allows the mixture of it to be burn harshly instantly. This combustion which is occurring in very high temperature produces gases. During this process while temperature raises it creates a pressure. As it gets confined in anyway, the pressure builds up and which becomes explosive. This can occur when the particles of the fuel are divided equally that it forms vapor or dust. Explosions occur in very small confined spaces or where there is high concentration of gases.
Importance of collisions between reacting particles:
When there are more particles moving in faster speeds, more collisions will occur during the short period of time. Hence there will be a greater chance of better collision (higher chance to make successful products). The more collision that occur, the faster the reaction rate of the overall reaction becomes. Hence increase rate of reaction at which collision occur will defiantly increase the rate of reaction. Reaction rate can increase due to increased temperature, increased...