As a chemical engineer with a strong background in thermodynamics and fluid dynamics, I can provide you with a detailed explanation of the conditions required for methane to become a liquid.

Methane, CH4, is the primary component of natural gas and is a colorless, odorless, non-toxic gas under standard conditions on Earth. To convert methane from a gas to a liquid, we need to consider the process of liquefaction, which involves lowering the temperature and/or increasing the pressure to bring the substance to a liquid state.

The liquefaction of methane is a critical process in the natural gas industry, as it allows for more efficient transportation and storage of this valuable energy resource. The process typically involves cooling the gas to a temperature below its critical temperature, which for methane is approximately -81.9 degrees Celsius (-115.4 degrees Fahrenheit). Below this temperature, methane can be liquefied by increasing the pressure.

The reference to Titan, one of Saturn's moons, is interesting in this context. Titan has a thick atmosphere that is primarily composed of nitrogen, with trace amounts of other gases, including methane. The surface temperature on Titan is extremely cold, averaging around -179.15 degrees Celsius (-290.47 degrees Fahrenheit). These conditions are far below the boiling point of methane, which is approximately -161.5 degrees Celsius (-258.7 degrees Fahrenheit) at atmospheric pressure. Therefore, methane can exist in a liquid state on Titan due to the combination of low temperature and atmospheric pressure.

It's important to note that the liquefaction process on Titan is not driven by industrial applications but rather by natural environmental conditions. The low temperatures and high pressures on Titan create a unique environment where methane can form lakes, rivers, and even rain, contributing to a hydrocarbon-based weather cycle.

In summary, for methane to be a liquid, it must be subjected to temperatures below its boiling point at atmospheric pressure, or pressures above its vapor pressure at a given temperature. On Earth, this typically involves industrial processes to cool and pressurize the gas. On Titan, the naturally occurring low temperatures and atmospheric conditions allow methane to exist in a liquid state, forming part of the moon's geology and weather patterns.

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On Earth, methane is a flammable gas, but Titan has no oxygen in its atmosphere that could support combustion. Also, the temperatures on Titan are so cold -- minus 300 degrees Fahrenheit (minus 149 degrees Celsius) -- that the methane can form liquid.Jul 27, 2006read more >>