Here’s a clear explanation:
Pressure
- Definition: Pressure is the force exerted per unit area. In gases, it is caused by gas particles colliding with the walls of their container.
- Intuition: The more frequent or stronger the collisions, the higher the pressure.
Units of Pressure
- Pascal (Pa): 1 Pa = 1 N/m² (force per area) – SI unit.
- Atmosphere (atm): Average air pressure at sea level ≈ 1 atm.
- mmHg / Torr: Pressure measured by a mercury column. 760 mmHg ≈ 1 atm.
- Bar: 1 bar ≈ 10⁵ Pa.
- Pascal to atm: 1 atm ≈ 101,325 Pa.
Measurement of Pressure
- Manometer: Measures the pressure of a gas in a container relative to atmospheric pressure using a U-shaped tube of liquid (usually mercury).
- Barometer: Measures atmospheric pressure. A column of mercury rises or falls depending on air pressure.
- Pressure Gauges: Mechanical or digital devices attached to gas containers to measure pressure directly.
Key Idea: Pressure depends on temperature, volume, and number of gas particles.