It is difficult to cook rice in an open vessel by boiling it at high altitudes because of

Options

A. low boiling point and high pressure
B. high boiling point and low pressure
C. low boiling point and low pressure
D. high boiling point and high pressure

Explanation

To solve the question regarding why it is difficult to cook rice in an open vessel by boiling it at high altitudes, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Boiling Point**: The boiling point of a liquid is the temperature at which its vapor pressure equals the atmospheric pressure. At this point, the liquid begins to turn into vapor.

2. **Effect of Altitude on Atmospheric Pressure**: As altitude increases, the atmospheric pressure decreases. This is due to the thinner air at higher altitudes, which means there are fewer air molecules exerting pressure.

3. **Vapor Pressure and Boiling Point Relationship**: For boiling to occur, the vapor pressure of the liquid must equal the atmospheric pressure. At higher altitudes, since the atmospheric pressure is lower, the vapor pressure required for boiling is also lower.

4. **Consequences of Lower Boiling Point**: Because the boiling point is lower at high altitudes, water will boil at a temperature that is less than 100°C (212°F). This means that the water will not reach the temperature needed to cook rice properly, as rice typically requires water to be at or near 100°C to cook effectively.

5. **Conclusion**: Therefore, it is difficult to cook rice in an open vessel at high altitudes because the boiling point of water is lower due to decreased atmospheric pressure, resulting in insufficient heat for proper cooking.

### Final Answer:
It is difficult to cook rice in an open vessel by boiling it at high altitudes because the boiling point of water decreases due to lower atmospheric pressure.

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