Air Pressure: Investigations

Earth’s Energy Budget

• Earth’s Energy Budget is also called Earth’s Energy Balance or Earth’s Radiation Budget
• Energy budget definition: accounting for energy income, use, and loss, especially in an ecosystem

Heat Transfer

• Energy in the form of heat can be moved in three ways: conduction, convection, radiation
• Conduction and convection require matter touching matter or matter in motion
• The space between the Sun and Earth is a vacuum with little to no matter
• Conduction and convection cannot transfer the Sun's heat to Earth
• Heat from the Sun is transferred through the emptiness of space as electromagnetic waves
• Infrared light, visible light, ultraviolet light, and X-rays are examples of electromagnetic waves

Energy Budget Vocabulary

• Absorb means liquids being soaked up by a sponge or paper towel
• The Sun's radiation can be absorbed by different parts of Earth
• Absorbent materials like sponges and paper towels soak up liquids easily
• Reflect means light being reflected by a mirror or aluminum foil
• Reflect means the Sun's radiation being reflected by different parts of Earth
• Emit is when something produces and sends out heat, light, gas, or a smell by physical or chemical processes
• Re-radiate is when the Sun’s radiation is re-radiated by different parts of Earth in the form of rays or waves
• Budget is a plan for how one spends or saves their money
• Budget definition: what happens to the sun’s energy when it reaches Earth
• Radiations budget is how the radiation is distributed
• Components of a budget should add up to 100%
• Balance is when one is not spending more money than they have
• Balance definition: how much of the sun's energy is absorbed by Earth and how much is reflected or re-radiated

Incoming vs Outgoing Radiation

• Incoming radiation is energy coming to Earth from the Sun
• Incoming radiation is energy transformed into heat that travels from the Sun to Earth
• Occurs over the course of about a year
• Incoming radiation includes ultraviolet, visible, and a portion of infrared energy from the sun
• Shortwave radiation is the term used for radiation from the Sun
• Outgoing radiation is energy leaving Earth, going back out into space
• Outgoing radiation is transformed heat that travels from the Earth back out to space over ~1 year
• Outgoing radiation is partly reflected solar radiation and partly radiation emitted from the Earth system, including the atmosphere

Solar Energy and Radiation on Earth

• Solar energy is either absorbed, reflected, or emitted (re-radiated)
• In diagrams, radiation is either incoming or outgoing
• The left side of a diagram (yellow arrows) illustrates incoming radiation that is absorbed or reflected
• The right side of a diagram (red arrows) illustrates energy that is emitted or re-radiated back to space by Earth’s surface, clouds, or the atmosphere

Earth’s Energy Budget Balance

• Over a year, the energy Earth receives from the sun equals the energy Earth sends back to space
• There is a balance of incoming radiation (amount of energy that reaches Earth) and outgoing radiation (amount of energy flowing from Earth back into space)
• In Earth’s energy budget, 30% is reflected
• 26% of incoming radiation is reflected by the atmosphere or clouds
• 4% of incoming radiation is reflected by land or oceans
• In Earth’s energy budget, 70% is absorbed
• 19% of incoming radiation is absorbed by clouds or the atmosphere
• 51% of incoming radiation is absorbed by land or oceans

Balanced Energy Budget

• The total amount of incoming radiation should equal the total amount of outgoing radiation over one year
• Earth maintains a stable temperature with a balanced energy budget
• If Earth takes in more radiation than it gives off, it will continually heat up
• If Earth takes in less radiation than it gives off, it will continually cool down

The Greenhouse Effect

• The earth-atmosphere system constantly tries to maintain an energy balance with incoming and outgoing radiation
• An imbalance in Earth’s energy budget due to the changes in the Earth system leads to a temperature change
• The Greenhouse Effect is a natural process warming the Earth’s surface and making life possible
• Greenhouse gases trap the sun’s energy at Earth’s surface, while allowing light through but blocking heat from escaping
• Methane (CH4), ozone (O3), carbon dioxide (CO2), and water vapor are important greenhouse gasses
• Earth has on average a surface temperature of ~15°C because of the greenhouse effect
• Without the greenhouse effect, Earth would be ~-18°C (below freezing)

The Enhanced Greenhouse Effect

• The enhanced greenhouse effect is when extra greenhouse gasses in the atmosphere trap too much of the sun’s energy
• Enhanced greenhouse effect causes a warming effect called global warming
• Warming is mostly caused by human-produced greenhouse gasses
• Emission of greenhouse gasses has rapidly increased because of humans, since the start of the Industrial Revolution (~1750)
• Human activities like burning fossil fuels have increased greenhouse gas concentrations in the atmosphere

Natural and Human created Sources of Carbon Dioxide

• Carbon dioxide occurs naturally in the atmosphere
• Natural sources of carbon dioxide: emissions from volcanic eruptions, forest fires, plant and animal respiration, decomposition of organic matter, outgassing from the ocean, and belches from ruminant animals
• Human action is causing a rapid build-up of carbon dioxide, faster than natural sinks can remove it
• Burning fossil fuels and deforestation are major sources of the extra carbon dioxide
• Expansion of farming, development, and industrial activities are releasing carbon dioxide and changing the balance of the climate system
• Essentially, humans have taken millions of years of carbon uptake by plants and returned it to the atmosphere in about 300 years

Climate Change

• Climate change includes changing weather patterns, rising sea levels, and ocean acidification
• Climate change is sometimes called global warming, but it is not just the temperature that is changing
• Changing weather patterns, changes in rain and wind, and increased frequency of extreme weather events are associated with climate change
• Global ice caps and glaciers are melting, and the oceans are becoming more acidic
• Temperature records from the last 100 years have shown that the rate of climate change is higher than the natural rate

Air Pressure

• Air is matter as it has mass and takes up space
• Air is invisible and it has not always been easy to prove that air is matter
• Air pressure is the force of air molecules
• When air pressure exists, air presses in all directions: up, down, on, and from all sides
• Anywhere there is air, there will be pressure

Air is Matter - Investigation 1

• A bucket or large bowl is filled with water
• A tissue is folded then taped to the bottom of the inside of a plastic cup
• The gravity will cause the tissue to fall if the tape wasn't tested to make sure it keeps the tissue in place when the cup is turned upside down
• The cup is pushed straight down to the bottom of the water
• The cup is then lifted straight back up
• When done correctly, the tissue should still be dry
• The cup was filled with air, so there was no room for water
• As air takes up space, that is why the tissue remains dry

Air is Matter - Investigation 2

• A balloon was put on an electronic balance to investigate if air has mass
• Mass is reported in grams (metric units)
• The balloons mass is greater after it is inflated
• A balloon gets bigger when it is inflated
• Air has mass and takes up volume

Proof That Air is Matter

• Air has mass, a balloon weighs more after being inflated
• Air has volume, a balloon gets bigger after being inflated
• Air trapped in a cup keeps a tissue dry when proper technique is used

Air Pressure and Altitude

• Airplanes use pressurized cabins for commercial flights to maintain air pressure
• The air that surrounds Earth has weight and pushes down on everything below it
• Air pressure changes with altitude (how high or how low you are compared to Earth's surface)
• Air pressure inside the plane is kept similar to the air pressure people are used to near the ground
• Airplanes fly high up in the sky and the air pressure is much lower up there
• An empty water bottle is closed high up in the sky and brought down to the surface, it might collapse because the pressure outside

Water Creates Pressure

• A styrofoam cup sent deep down under the ocean will have all of the air squeezed out of it because of the increased pressure

Air Pressure Investigation - Materials

• Syringe
• Plunger
• Plastic Tube
• Foam Cube
• Binder Clip or Clamp
• A medical syringe is used when giving people a shot, the syringe in the investigation is not for medical purposes

Air Pressure Investigation - Vocabulary

• Open system is a way of getting in and out
• Closed system is where the air does not have a way of getting in or out
• Compressed means squeezed
• Decompressed means released and expanded

Closed System

• When the plastic tube is folded in half with the binder clip, it creates a closed system where air does not have a way of escaping
• There is a limited amount of space to fill inside the syringe
• In a closed system, It is difficult to push the plunger down because air is taking up space
• The plunger will only go down a little bit when pressed
• The air is forced into a smaller space and the air pressure increases
• When the plunger is let go, the increased air pressure will push the plunger upward
• The number of air molecules does not change when air is compressed in a closed system
• In a closed system, the air molecules cannot escape, that is why the pressure increases
• Applying pressure to the plunger with a closed system compresses the air
• Pulling the plunger upwards creates a vacuum since there is no way for air to move inside the space

Foam Cube Investigation

• A foam cube is used to see what happens to the air because foam is made with space between the molecules filled with air
• The foam cube is put inside of the syringe and the tube is clamped to create a closed system
• The foam cube gets compressed when the plunger is pushed downward because the air gets compressed
• The foam cube gets decompressed (relaxes/expands) when the plunger is released because the air decompresses
• The foam cube is seeing what is happening to the air
• Air is pressing on the foam cube, that is air pressure

Composition of Air - Vocabulary

• Trace amount: a very small amount
• Abundant amount: a large amount
• Variable amount: changing
• Permanent amount: a fixed amount that does not change

Chemistry and Math Connection

• Air is a mixture of elements and compounds, not a pure substance, element, or a compound
• Elements in the air include Nitrogen (N2), Oxygen (O2), Ozone (O3), Argon (Ar), Neon (Ne), Helium (He), and Hydrogen (H2)
• Compounds in the air include Carbon Dioxide (CO2), Methane (CH4), Nitrous Oxide (NO), and Water Vapor (H2O)
• 78% of air is nitrogen (N2), 21% of air is oxygen (O2), and all other gases combined make up 1% of the composition
• Humidity is the measure of the amount of water vapor in the air

Variable Gases

• The amount of variable gases changes in response to activities in the environment
• Water vapor (H2O) is a variable gas, as is the amount of water vapor, which changes with the weather and measures the humidity in the air
• Carbon dioxide (CO2) is a variable gas that is produced naturally by animals and used by plants, and is seen as an air pollutant when created by burning fossil fuels
• Methane (NH4) is a variable gas produced digestively especially by cows, and is considered an air pollutant created by coal mines, oil wells, gas pipelines, and rice cultivation.
• Greenhouse gases are variable gases that trap thermal energy and are important for life on Earth
• Without enough greenhouse gases the Earth would be too warm during the day or too cold at night
• Too much heat being trapped by increased amounts of greenhouse gasses can cause Earth to get too warm

Modeling the Air

• A plastic bag and 100 pieces of cereal can create a good model showing the different gases
• A cereal model of air can use different colors for nitrogen (78%), oxygen (21%), and trace gases (1%)
• A more realistic model does not group gases together, but mixes everything together
• An air bag pictograph can be created with 100 squares, with each square representing 1%
• An air bag circle graph can be created with 10 slices representing 10%, with each slice broken into 10 parts to represent 1%