As a chemical engineering expert with a focus on combustion and safety, I'd like to address the question of whether gasoline can be ignited by a cigarette. This is a topic that involves understanding the principles of combustion, specifically the ignition point of a substance and the heat transfer mechanisms involved.

Firstly, let's define what it means for a substance to be ignited. Combustion is a chemical reaction that occurs between a fuel and an oxidizer, usually producing heat and light in the form of a flame. For gasoline, the fuel is the hydrocarbons present in the liquid, and the oxidizer is typically oxygen from the air.

Now, to the specifics of the question. When we talk about the flammability of gasoline, we are referring to its vapor, not the liquid itself. Gasoline vapor is indeed more flammable than the liquid because the vapor is in a state where it can more readily mix with air to form a combustible mixture. This mixture is known as the flammable range or explosive limit, where the concentration of vapor in air is within a certain range that can support combustion.

The ignition point of a substance is the temperature at which it will spontaneously ignite in a normal atmosphere without an external source of ignition. For gasoline, this temperature is quite high, typically above 300°C (572°F). A lit cigarette, on the other hand, has a much lower temperature. The heat from the cigarette's ember is not sufficient to reach the ignition point of gasoline. However, the cigarette's flame could potentially heat the air around it to a point where it could ignite the vapor if the conditions are right.

It's important to note that the liquid gasoline will not ignite from the heat of a cigarette. The liquid acts as a heat sink, absorbing the heat from the cigarette and preventing it from reaching the necessary temperature to ignite the vapor. This is why pouring gasoline on a fire is not recommended; the liquid can actually help to extinguish the flames by absorbing heat.

However, if the gasoline vapor is present in the right concentration and the cigarette is introduced into this environment, the cigarette could act as an ignition source. The heat from the cigarette could ignite the vapor-air mixture, causing a flash fire. This is a rapid combustion that occurs when a flammable vapor is ignited in a confined space.

In summary, a lit cigarette is not hot enough to ignite liquid gasoline due to the high ignition point of the liquid and its ability to absorb heat. However, under the right conditions, such as in the presence of gasoline vapor at the right concentration, a cigarette could potentially ignite the vapor and cause a fire. It's crucial to handle gasoline with care and avoid any potential sources of ignition to prevent accidents.

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It seems the vapour is more flammable than the liquid. The liquid will douse the cigarette. A lit cigarette isn't hot enough to ignite the gasoline. A smoking cigarette on the other hand may get hot enough to be able to ignite the gas however.read more >>