Water boils at 120°C in a pressure cooker because the increased pressure inside the cooker raises the boiling point of water. Normally, water boils at 100°C at standard atmospheric pressure, but the pressure cooker traps steam, increasing the pressure and allowing water to reach higher temperatures before boiling. This higher temperature cooks food faster and more efficiently.
The boiling point of water decreases with altitude, so the temperature at which water boils would be lower at a Himalayan peak compared to the seashore. This is because air pressure decreases with increasing altitude, which affects the boiling point of water.
In pressure cooker temperature rises to about 120 degree centigrade due to higher pressure than atmospheric pressure. Witch makes it makes food to get cooked faster than in open pot where water boils at 100 degree centigrade. Pressure cooker becomes essential at high altitude where water may boil at about 70 degree centigrade.
To sterilise effectively the water in the autoclave needs to reach a temperature of 120°C. Since water at atmospheric pressure boils at 100°C, a higher pressure is needed to reach that temperature.
Normally you have a pressure of approx. 2 bar (2kPa) in a pressure cooker.At this pressure the boiling point of water is 120 0C (393 K) or 247 FSee the Related Questions to the left for more information about how pressure affects the boiling point of water.
The answer depends primarily on the scale that you are using. On the Celsius (or Centigrade) scale, under normal atmospheric pressure, pure water boils at 100 deg.
Water at standard atmospheric pressure would be steam (vapor) at 120 degrees C. However, that's not much above the boiling point. If you pressurize the steam, it's easy to keep 120 degree C water liquid. This is how a "pressure cooker" works; it prevents the water vapor from expanding much, which causes the pressure to increase.
A pressure cooker minimizes the escape of fluids or air. The build-up of air and fluid increases the pressure inside the cooker, which also increases the boiling point. An open kettle allows the fluid and air to escape, heat is lost thus cooking time is longer.
The boiling point (BP) of water at 1489 torr is 120 degrees Celsius because the boiling point of a liquid increases with pressure. Standard atmospheric pressure is 760 torr, at which water boils at 100 degrees Celsius. At higher pressures, such as 1489 torr, the increased pressure requires more heat energy to allow water molecules to escape into the vapor phase, thus raising the boiling point to 120 degrees Celsius.
At 0,5 bar water boils at about 176 °F or 80 °C At 1 bar water boils at about 212 °F or 100 °C At 2 bar water boils at about 250 °F or 120 °C See the link below for a graph, a table and an explanation.
Water boils at 100 Celsius at a mercury barometer reading of 760mm. At higher pressures, the boiling point is higher. Conversely, at lower pressures - high up mountains, water boils at much lower temperatures.
Pressure doesn't change when you change substance, 120 PSI in water equals 120 PSI in air.
Water boils at 212 degrees Fahrenheit at sea level.