Atmospheric Pressure

Atmospheric pressure is the force exerted onto a surface by the weight of the air above that surface in the Earth's atmosphere. It is also known as air pressure. The atmosphere is composed of a mixture of gases, primarily nitrogen (78%) and oxygen (21%), with trace amounts of other gases.

Factors Affecting Atmospheric Pressure

The atmospheric pressure at any point is influenced by several factors:

• Altitude: Atmospheric pressure decreases with increasing altitude. This is because there is less air above, exerting downward force.
• Temperature: Warmer air has lower pressure, while colder air has higher pressure.
• Humidity: Moist air is less dense than dry air, so it exerts less pressure.

Units of Measurement

Atmospheric pressure is typically measured in several units, including:

• Millimeters of Mercury (mmHg)
• Inches of Mercury (inHg)
• Pascals (Pa)
• Atmospheres (atm)

Effects of Atmospheric Pressure

Changes in atmospheric pressure can have various effects, such as influencing weather patterns, affecting the boiling point of liquids, and impacting human and animal physiology.

Study Guide

Here are some key points to remember about atmospheric pressure:

1. Define atmospheric pressure and explain its relationship to the weight of the air above a surface.
2. List and describe the factors that affect atmospheric pressure.
3. Identify the units of measurement used for atmospheric pressure.
4. Explain the effects of atmospheric pressure on weather, boiling points, and living organisms.