A close bottle containing water at room temperature was taken to the Moon and then the lid is opened. The water will

When a closed bottle of water at room temperature is opened on the Moon, the water will boil. This occurs because the Moon lacks a substantial atmosphere, creating a near-vacuum environment [2]. The boiling point of any liquid is dependent on the ambient pressure; as pressure decreases, the boiling point also decreases [1]. In a vacuum, the external pressure is effectively zero, which is far below the vapor pressure of water at room temperature. Consequently, the water molecules meet almost no resistance from air molecules and transition rapidly into the gaseous state [1]. While the rapid evaporation causes cooling that may eventually lead to some water freezing into a fine mist or ice, the immediate physical reaction upon opening the bottle in a vacuum is vigorous boiling. Chemical decomposition into oxygen and hydrogen would require significant energy input like electrolysis, which is not present here.

Sources

1. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 2: The Solar System > There are Several Disadvantages to the Moon as a Colony Site > p. 29
2. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 3: Geological Time Scale The Evolution of The Earths Surface > 3. Geological Time Scale – The Evolution of The Earth's Surface > p. 43