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What Causes Air Pressure? — Reading Comprehension

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"This engaging science passage for middle school students explains the concept of air pressure. It covers the fundamental cause of air pressure—the weight of the atmosphere—and explores the key factors that influence it: altitude and temperature. Students will learn how these factors lead to the creation of high and low-pressure systems, which in turn drive weather patterns like wind. The text also connects the concept to real-world applications, such as why breathing is difficult at high altitudes and how meteorologists use barometers to forecast weather. The passage is designed to align with NGSS standards related to Earth's systems and physical science, providing a solid foundation for understanding atmospheric phenomena."

CONTENT PREVIEW

Air pressure is a fundamental concept in meteorology and physics, defined as the force exerted by the weight of air molecules on a surface. It is the result of countless air particles, or molecules, constantly moving and colliding with everything around them. Imagine a huge, invisible ocean of air, known as the atmosphere, stretching high above Earth's surface. We live at the bottom of this ocean, and the immense weight of the air column above us is what creates atmospheric pressure. This pressure is not just a downward force; because air molecules move in all directions, they exert pressure in every direction, which is why a balloon inflates evenly.

Two primary factors influence air pressure: altitude and temperature. As altitude increases, air pressure decreases. This is because at higher elevations, there is less air above you, so the weight of the air column is lighter. The air molecules also become more spread out and less dense. This is why it's harder to breathe on a tall mountain—the air is "thinner" and contains fewer oxygen molecules. Conversely, at sea level, the air molecules are compressed by the entire atmosphere above, making the air denser and the pressure higher.

Temperature also plays a crucial role. When air is heated, its molecules gain kinetic energy and move faster, spreading farther apart. This causes the air to become less dense and to rise, resulting in an area of low pressure. Conversely, when air cools, its molecules slow down, move closer together, and become denser. This cool, dense air sinks toward the surface, creating an area of high pressure. The movement of air from high-pressure areas to low-pressure areas is what we experience as wind, making air pressure differences a major driver of weather patterns.

Changes in air pressure are key to predicting the weather. A falling barometer reading, which indicates decreasing air pressure, often signals that a storm system or other unsettled weather is approaching. A rising barometer, on the other hand, usually suggests that a high-pressure system is moving in, bringing clear skies and fair weather. Meteorologists use instruments like barometers to measure these pressure changes and forecast conditions.

Fun Fact: A standard column of air, from sea level to the top of the atmosphere, weighs about 14.7 pounds per square inch (or about 10.1 newtons per square centimeter). This is roughly the weight of a bowling ball resting on a single fingernail!

What is the definition of air pressure?

The speed of windThe force exerted by the weight of airThe amount of water vapor in the airThe temperature of the atmosphere

How does air pressure change as altitude increases?

It increases.It decreases.It remains the same.It fluctuates unpredictably.

What causes a low-pressure area to form?

Cool air sinkingWarm air risingHigh humidityStrong wind currents

Why is it harder to breathe at the top of a tall mountain?

The air is warmer.The air is denser.There are fewer oxygen molecules.The wind is too strong.

What is the primary cause of wind?

Changes in humidityDifferences in air pressureThe Earth's rotationThe moon's gravitational pull

According to the passage, what does a rising barometer reading typically indicate?

Approaching stormsHigh windsClear, fair weatherIncreased humidity

Which of the following is an example of an area with high air pressure?

The top of a tall mountainThe center of a hurricaneA region of sinking, cool airA region of rising, warm air

Which statement best summarizes the main idea of the passage?

Air pressure is only affected by temperature.Air pressure is a significant force with several influencing factors.Meteorologists can only predict weather using wind speed.High altitude is the only cause of low air pressure.