In which state must fuel be for ignition to occur?

For ignition to occur, fuel needs to be in a state that can mix with an oxidizer, typically oxygen, to support combustion. In this context, the gas state is particularly significant because it allows for effective mixing with oxygen, creating the necessary conditions for ignition.

Gas-phase fuels expand and disperse in the air, which facilitates the formation of the combustible mixture. This is essential for initiating combustion. While solids and liquids can burn, they often require additional processes, such as vaporization or conversion to gas, before they can ignite.

Therefore, the gas state represents the most immediate and effective condition for ignition to occur, as it allows for quick and efficient interaction with an oxidizing agent, leading to combustion.