The boiling point of ethane, notated as C2H6, is -128.2 degrees Fahrenheit. The boiling point of a substance describes the point at which its vapor pressure equals the atmospheric pressure at standard temperature and pressure conditions.
When the vapor pressure drops below the atmospheric pressure, the substance changes its state of matter from a liquid to a gas. The kinetic energy of particles relates to the vapor pressure in a substance and is higher in a gas than in a liquid. Standard temperature and pressure conditions assume a temperature equal to 68 degrees Fahrenheit and that the pressure is one standard atmosphere unit.