We often think of the freezing point as being the temperature where water freezes (273.15 K). There are several scales for measuring temperature, for simplicity lets use Kelvin here. If you have watched a pot of water boil away you are aware the water has 3 states, vapor (steam), Liquid (water) & solid (ice). The point where a solid turns to a liquid as often called the melting point.
According to Wikipedia temperatures on the moon range from 26 K to 390 K. If we look at a list of melting points we see that element like Hydrogen & Neon have melting points below 26 K but they also boil around 20 - 27 K, so they would not be a good liquid for using on the moon. As they would vaporize in all but the coldest lunar winter day.
The lunar equator has temperatures ranging from 100 k to 390 K. As we look at the list of melting points there are some that are liquid around 100 k but they all have fairly short liquid ranges Oxygen has one of the bigger ranges of about 45 degrees but that is between 54 K and 90 K. It seem our biggest risk then is not in finding an element that will flow during lunar cold spells, but rather one that will not boil during the warm spells. Even water which boils at 373.16 K can boil on the moon.
There are also considerations for pressure, as it can modify the melting & boiling points. In short there is no single element that will work as liquid on the moon, so any fluid would either need to be compound or solution (antifreeze) to keep from freezing, some heat would likely be required for the coldest periods, and pressures maintained to prevent boiling from extremes of temperature or exposure to vacuum.
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