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Air Pressure — Reading Comprehension

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MS-ESS2-5

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This middle school science passage explores the concept of air pressure, aligning with NGSS standard MS-ESS2-5. Students will learn how air pressure is the force exerted by air molecules pressing on Earth's surface, why it changes with altitude, and how it drives changes in weather and wind. The passage explains scientific tools like barometers, units of measurement, and the function of isobars on weather maps. It discusses the differences between high- and low-pressure systems and their impact on weather phenomena such as clear skies or storms. Real-world applications, such as predicting weather and understanding atmospheric science, are included to connect the concept with daily life. The passage is supported by a glossary, quiz, writing prompts, and two graphic organizers. Audio integration and English/Spanish versions make this resource accessible for diverse learners. This resource is ideal for grades 6-8 science classrooms and supports the development of scientific thinking and literacy.

CONTENT PREVIEW

Air pressure is a fundamental concept in atmospheric science. It refers to the force that air molecules exert as they press against the surfaces around us. The weight of the entire atmosphere above Earth's surface creates this pressure. Understanding air pressure is crucial for predicting weather changes and explaining how air moves across our planet.

How Air Pressure Works
At any moment, thousands of air molecules are moving rapidly in all directions. When these molecules collide with surfaces, they exert a force called pressure. The atmosphere is thickest at sea level, which means there are more molecules above you, resulting in higher pressure. As you move to higher altitudes—like climbing a mountain—there are fewer molecules above, and air pressure decreases. For example, at the top of Mount Everest, air pressure is only about 300 millibars (mb), compared to the standard sea level pressure of 1013.25 mb. Scientists use instruments called barometers to measure air pressure. A mercury barometer uses the height of liquid mercury to indicate pressure, while an aneroid barometer uses a sealed, flexible chamber.

Air Pressure and Weather Systems
Differences in air pressure drive the movement of wind. Air naturally moves from areas of high pressure to areas of low pressure. This movement creates wind, which can vary from a gentle breeze to strong storms. High-pressure systems are associated with sinking air, leading to clear skies and stable weather. In contrast, low-pressure systems involve rising air, which cools and forms clouds, often resulting in precipitation or storms. Weather maps use lines called isobars to connect points of equal pressure. Closely spaced isobars indicate stronger winds because the pressure changes rapidly over a short distance.

Measuring and Applying Air Pressure
Air pressure is measured in units such as millibars (mb), inches of mercury, atmospheres, or Pascals. Weather experts monitor air pressure to predict changes in the weather. For example, a sudden drop in pressure can signal an approaching storm. Understanding air pressure also helps pilots, mountain climbers, and athletes prepare for changes in oxygen availability and weather conditions. On a larger scale, air pressure patterns help explain global wind systems and climate zones.

Understanding air pressure connects to larger scientific principles, such as the behavior of gases (the gas laws) and the cycling of energy in Earth's systems. By studying air pressure, scientists can better predict weather events, prepare for natural disasters, and understand the interconnected processes that shape our environment.

Interesting Fact: The highest barometric pressure ever recorded at sea level was 1084 millibars in Siberia in 1968—a result of extremely cold, dense air.

What does air pressure measure?

The force of air molecules pressing on a surfaceThe temperature of the atmosphereThe weight of a solid objectThe speed of wind

Which tool do scientists use to measure air pressure?

BarometerThermometerAnemometerRain gauge

What happens to air pressure as altitude increases?

It decreasesIt increasesIt stays the sameIt disappears

What causes wind to blow?

Differences in air pressureThe Sun's heatThe Earth's rotationCloud formation

What is the standard air pressure at sea level in millibars (mb)?

1013.25 mb300 mb500 mb1084 mb

What does the word 'isobars' mean as used in the passage?

Lines connecting points of equal air pressure on a mapInstruments to measure wind speedTypes of weather cloudsUnits for measuring temperature