Pressure exerted by a gas
Explanation
The unit 'atmosphere' (symbol: atm) is a standard unit of measurement used in physics and chemistry to quantify pressure. It was historically defined based on the average atmospheric pressure at mean sea level.
Detailed Analysis:
- Density of air is Incorrect: Density is defined as mass per unit volume. Its SI unit is kilograms per cubic meter (kg/m³). It is not measured in atmospheres.
- Pressure exerted by a gas is Correct: The 'atmosphere' is a unit of pressure. In the context of gases, pressure is the force exerted by gas particles colliding with the walls of their container. One atmosphere (1 atm) is defined as exactly 101,325 Pascals (Pa). It is commonly used to describe the pressure of gases in various thermodynamic states.
- Mass of the atmosphere is Incorrect: Mass is a fundamental property representing the amount of matter in an object. The SI unit for mass is the kilogram (kg).
- Volume of gases is Incorrect: Volume measures the three-dimensional space occupied by a substance. Common units for volume include cubic meters (m³) and liters (L).
Key Takeaway:
The unit 'atm' is exclusively used to measure pressure. The relationship between common pressure units is: 1 atm = 760 mmHg = 760 Torr = 101.325 kPa.