Barometric Pressure
Definition and meaning of Barometric Pressure in chemistry.
Barometric pressure is the force exerted by the atmosphere on Earth's surface, typically measured with a barometer. It varies with altitude, weather conditions, and temperature.
In more detail
At sea level, standard atmospheric pressure is approximately 101.325 kilopascals (101.325 kPa or 1 atm), caused by the weight of all air above a given point. Barometric pressure measurements are crucial in meteorology, aviation, and chemistry because they affect boiling points, gas behavior, and weather patterns. Lower pressure indicates approaching storms, while higher pressure suggests stable conditions. Pressure decreases exponentially with altitude because less atmosphere exists above higher elevations.
Key facts
| Standard Pressure | 101.325 kPa (760 mmHg or 1 atm) |
|---|---|
| Common Units | kPa, mmHg, atm, bar, psi |
| Effect on Boiling | Lower pressure allows liquids to boil at lower temperatures |
| Field | Physical Chemistry |
At sea level on a clear day, a barometer reading shows approximately 760 mmHg (101.3 kPa), the standard atmospheric pressure. In Denver, Colorado, at about 1 mile elevation, barometric pressure is typically around 640 mmHg due to the reduced atmospheric column above.
Frequently asked questions
Why does barometric pressure change with altitude?
As altitude increases, there is less air above a point, resulting in lower atmospheric pressure since pressure is caused by the weight of the atmosphere.
How does barometric pressure affect boiling points?
Lower atmospheric pressure allows liquids to boil at lower temperatures because gas molecules can escape more easily from the liquid surface.