How To Calculate Atmospheric Pressure — Reading Comprehension

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This audio-integrated reading passage, "The Pressure of Air: Calculating Atmospheric Pressure," explores the concept of atmospheric pressure and how it's calculated. It defines key terms like barometer and Pascals, and explains the factors that influence air pressure, such as altitude. Students will learn that atmospheric pressure is the force exerted by the weight of the air above us. The passage also touches on the simplified formula for pressure, P=ρ⋅g⋅h, and explains why our bodies are not crushed by this force. The information aligns with the NGSS Disciplinary Core Idea of PS1.A: Structure and Properties of Matter, as it discusses the properties of air and its effect on our environment. This resource is perfect for a middle school science lesson on the properties of matter and forces.

CONTENT PREVIEW

A picture of a barometer with two gauges, one showing high pressure and one showing low pressure. — A barometer measures atmospheric pressure.

The Earth is surrounded by a vast layer of air called the atmosphere. This layer of air, which extends for hundreds of miles above the surface, has weight. The force exerted by this weight on the Earth's surface and on all objects within it is known as atmospheric pressure. We can think of it as a huge, invisible ocean of air pressing down on everything.

Atmospheric pressure is not constant; it changes with altitude. The higher you go, the less air is above you, which means there is less weight pressing down. This is why the air feels "thinner" at high altitudes, like on top of a mountain. Conversely, at lower altitudes, such as at sea level, the entire column of air above you creates the maximum pressure.

Scientists measure atmospheric pressure using a tool called a barometer. One common type is the mercury barometer, which uses a column of mercury. The height of this mercury column changes with the pressure of the air. A higher column of mercury indicates greater atmospheric pressure. The standard atmospheric pressure at sea level is often expressed in different units, such as 1 atmosphere (atm), 101,325 Pascals (Pa), or 760 millimeters of mercury (mmHg). The formula for calculating atmospheric pressure (in a simplified way, for a static fluid) is P=ρ⋅g⋅h, where P is pressure, ρ (rho) is the density of the fluid (like mercury in a barometer), g is the acceleration due to gravity, and h is the height of the fluid column.

Your body is not crushed by this immense pressure because the fluids and gases inside your body exert an outward pressure that balances the external atmospheric pressure, creating a state of equilibrium.

Fun Fact: The pressure on your body from the atmosphere is about 14.7 pounds per square inch, which is roughly the weight of a bowling ball on every square inch of your skin!

What is the name of the tool used to measure atmospheric pressure?

thermometeraltimeterbarometeranemometer

Which of the following units is used to express standard atmospheric pressure?

metersgramsPascalsNewtons

Why does air feel "thinner" at higher altitudes?

The air gets colder at higher altitudesThere is less air pressing down from aboveThe Earth's gravity is weaker at higher altitudesAir molecules expand at higher altitudes

According to the passage, why is a person's body not crushed by atmospheric pressure?

The body's bones are strong enough to resist the pressureThe body's internal pressure balances the external pressureThe skin is too thick for the pressure to have an effectThe pressure is only exerted on the top of the head

What would happen to the reading on a barometer if you carried it to the top of a very tall mountain?

The reading would increaseThe reading would decreaseThe reading would not changeThe barometer would stop working

A scuba diver is at a depth where the pressure is twice that of the atmospheric pressure at sea level. If they ascend to the surface too quickly, the pressure difference can cause health problems. What principle from the passage explains this?

The barometer reading would change too fastThe internal pressure of the diver’s body would not have time to adjust to the lower external pressureThe density of water decreases as they ascendThe effect of gravity on the diver’s body increases

A student is trying to create a homemade barometer. They know that atmospheric pressure can be calculated using the formula P=ρ⋅g⋅h. If they use water instead of mercury in their barometer, what would they likely observe?

The height of the water column would be much shorter than a mercury columnThe water column would have to be much taller to show the same pressureWater is too light to be used in a barometerThe reading would be less accurate because water is not as dense as mercury

A weather forecaster observes that the atmospheric pressure is steadily decreasing. Based on this information and the passage, what might they predict about the upcoming weather?

It will be a sunny and calm dayIt will be very windy and coldA storm or change in weather is likely approachingThe temperature will start to rise