Question

I have learned that LIQUID water does not exceed its boiling point temp of 100 degrees C. (then phase changes to steam) but is it possible for water to be at temps over 100??

Answer 1

Ans) Surely we can say that water exists in LIQUID state at temperatures over 100 oC with paritcular conditions only.

* first we need to know what is boiling point, it is a temperature at which vapour pressure of water is equal to atmospheric pressure (surrounding pressure). with this relation simply we can understand, boiling point of a substance is function of pressure.

* For water, it boils completely at temperature of 100 oC and pressure 1 atm. that means water is boiling point is 100 oC at atmospheric pressure (101325 Pa). if you want to boil water at very high altitudes like top of the mountains, there is less atmospheric pressure (<101325 pa). so vapor pressure of water equals to surrounding pressure at low temperatures. that means it boils below 100 oC.

* At high pressures ( >101325 Pa), vapore pressure of water equals to surrounding pressure. so it boils at high temperatures over 100 oC. Untill then water exists in liquid state over 100 oC .

Observe this P vs T graph.

* pressure > 1 atm, water exits as a liquid over 100 oC.

Pressure = 218 atm, boiling point = 374 oC, that means at 300 oC also water exists as a liquid