When stored refrigerated, butane is in what form?

• A. Gas
• B. Solid
• C. Plasma
• D. Liquid

Answer: (D)

Phase state depends on temperature and pressure. Butane has a boiling point around -0.5°C at atmospheric pressure, so when it’s stored in a refrigerated, pressurized cylinder, most of the contents exist as a liquid rather than a gas. Keeping it as a liquid allows a large amount to be stored in a compact space; as gas is drawn off, liquid butane boils to replace it, maintaining pressure. This is why refrigerated storage yields a liquid form. The other forms would require conditions far outside typical refrigeration: a gas would occur if the temperature were above the boiling point and pressure low; solid would require much colder temperatures.