pressure and melting or boiling point relation....

Asked by ragini sathe | 4th Mar, 2012, 12:56: AM

Expert Answer:

Under normal atmospheric pressure, ice melts at 0 °C and water boils at 100 °C. However, this can change if the air pressure changes. The melting point of ice is lowered if the pressure on the ice is increased.
For eg. if we tie a wire around a large ice block, the ice in contact with the wire melts since it is subjected to a large pressure. The wire sinks through the water which then freezes again. When the water freezes, energy is given out and melts the ice below.

Experiments also show that the boiling point of water is raised if the pressure above water is increased; it is lowered if the pressure is reduced. This explains why water boils at 70 °C up in the Himalaya. An application of this effect is the pressure cooker. A pressure cooker traps steam inside it, raising the pressure to about twice the atmospheric pressure. As a result, the water boils at 120 °C. Food cooks quicker at the higher temperature.

Answered by  | 4th Mar, 2012, 10:06: PM

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