A bottle of water at `0^@`C is opened on the surface of Moon. What happens?

Options

A. water freezes
B. water will boil
C. water decomposes into hydrogen and oxygen
D. none of these happens

Explanation

To solve the question of what happens when a bottle of water at 0°C is opened on the surface of the Moon, we need to consider the conditions present on the Moon compared to those on Earth.

### Step-by-Step Solution:

1. **Understanding the Conditions on the Moon**:
- The Moon has a very thin atmosphere, which means that the atmospheric pressure is significantly lower than that on Earth. The average atmospheric pressure on the Moon is about 1/100,000th of Earth's atmospheric pressure.

2. **Boiling Point of Water**:
- The boiling point of water is influenced by atmospheric pressure. At sea level on Earth (1 atm), water boils at 100°C. However, as the atmospheric pressure decreases, the boiling point of water also decreases.

3. **Vapor Pressure of Water**:
- At 0°C, the vapor pressure of water is approximately 0.6 kPa. This is much lower than the atmospheric pressure on Earth but is still significant compared to the very low pressure on the Moon.

4. **What Happens When the Bottle is Opened**:
- When the bottle of water is opened on the Moon, the atmospheric pressure around the water is so low that the vapor pressure of the water (0.6 kPa) will exceed the surrounding pressure almost immediately.

5. **Conclusion**:
- Due to the extremely low atmospheric pressure on the Moon, the water will start to boil as soon as the bottle is opened. It will not freeze because the boiling point is lower than 0°C under these conditions.

Thus, the correct answer is that **the water will boil** when the bottle is opened on the surface of the Moon.

### Final Answer:
**Water will boil.**

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