Complete the following sentences :
Water can be made to boil at `115^@`C by …................... pressure over its surface.

Explanation

To complete the sentence, we need to understand the relationship between pressure and the boiling point of water. Here's the step-by-step solution:

1. **Understanding Boiling Point**: The boiling point of a liquid is the temperature at which its vapor pressure equals the external pressure surrounding the liquid. For pure water, this is typically 100°C at standard atmospheric pressure (1 atm).

2. **Effect of Pressure on Boiling Point**: When the external pressure is increased, the boiling point of the liquid also increases. This means that water can boil at a temperature higher than 100°C if the pressure above it is increased.

3. **Given Temperature**: In this question, we are asked about water boiling at 115°C. This indicates that the pressure above the water must be higher than standard atmospheric pressure to allow it to boil at this elevated temperature.

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