Atmospheres

Definition

An atmosphere is the layer of gases surrounding a planet or other celestial body that is retained by the body's gravity. It plays a crucial role in the gas pressure and temperature of a planet, which are key factors in the Ideal Gas Law.

5 Must Know Facts For Your Next Test

1. The Earth's atmosphere is composed primarily of nitrogen (78%) and oxygen (21%), with small amounts of other gases such as argon, carbon dioxide, and water vapor.
2. Atmospheric pressure decreases with increasing altitude, as the weight of the air above decreases.
3. The ideal gas law (PV = nRT) describes the relationship between the pressure, volume, amount, and temperature of a gas, which is influenced by the composition and properties of the atmosphere.
4. Partial pressures of individual gases in a mixture contribute to the total pressure according to Dalton's law of partial pressures.
5. Atmospheric pressure is commonly measured in units of atmospheres (atm), millimeters of mercury (mmHg), or pascals (Pa).

Review Questions

• Explain how the composition and properties of an atmosphere affect the gas pressure within that atmosphere.
  • The composition and properties of an atmosphere directly influence the gas pressure within that atmosphere. The relative amounts of different gases, their molecular weights, and the overall density of the atmosphere determine the total gas pressure. Additionally, changes in temperature and altitude can affect the gas pressure, as described by the ideal gas law. For example, a decrease in atmospheric pressure with increasing altitude is due to the reduced weight of the overlying air.
• Describe how the ideal gas law relates to the behavior of gases in an atmosphere.
  • The ideal gas law, expressed as PV = nRT, is a fundamental equation that describes the relationship between the pressure, volume, amount, and temperature of a gas. In the context of an atmosphere, this law governs the behavior of the gases present, such as how changes in temperature or the amount of gas (e.g., due to chemical reactions or diffusion) affect the overall pressure. The ideal gas law is crucial for understanding the dynamics and properties of atmospheric gases, including the partial pressures of individual components and how they contribute to the total atmospheric pressure.
• Analyze how the concept of partial pressure relates to the overall composition and pressure of an atmosphere.
  • The concept of partial pressure is essential for understanding the composition and pressure of an atmosphere. According to Dalton's law of partial pressures, the total pressure of a gas mixture is equal to the sum of the partial pressures of the individual gases. In an atmosphere, the partial pressures of the constituent gases, such as nitrogen, oxygen, and carbon dioxide, contribute to the overall atmospheric pressure. The relative concentrations of these gases, as well as their individual molecular properties, determine their respective partial pressures and the resulting total pressure of the atmosphere. This relationship is crucial for analyzing the behavior and properties of atmospheric gases, as well as for understanding the potential impact of changes in atmospheric composition on overall pressure and other environmental factors.

Related terms

Gas Pressure:

The force exerted by the weight of gas molecules per unit area on the walls of a container or the surface of an object.

Ideal Gas Law:

The relationship between the pressure, volume, amount, and temperature of a gas, expressed as the formula PV = nRT.

Partial Pressure:

The pressure that each individual gas would exert if it alone occupied the same volume as the mixture.