Final answer:
Butane (C4H10) is a gas at room temperature and pressure, but in cigarette lighters, it's compressed into a liquid. When the lighter's valve is opened, the butane reverts to gas, allowing it to ignite.
Step-by-step explanation:
Butane, C4H10, is indeed a gas at room temperature and atmospheric pressure, but it is found in liquid form in some cigarette lighters due to being compressed. When butane is placed under increased pressure inside the lighter's fuel compartment, the molecules are forced closer together. This process exceeds the attractive forces between the molecules compared to their kinetic energy, leading to condensation and thus a liquid state.
Liquefaction of gases like butane is possible if the gas is compressed and the temperature is kept below its critical temperature. In the case of cigarette lighters, the butane is compressed within the storage compartment which allows it to remain as a liquid. When the valve of the lighter is opened, the pressure is released, and the butane reverts back to its gaseous state as it exits the lighter, enabling it to ignite and produce a flame.