Rationale
On May 10, 2013 the National Oceanic and Atmospheric Administration reported that the levels of carbon dioxide (CO 2) in the atmosphere had risen to 400 parts per million (400 ppm). Even though there are seasonal circumstances that contribute to the increase and/or decrease of CO 2 in the atmosphere (for example, CO 2 levels lower during the summer since leaf growth pulls out billions tons of carbon out of the air), this new milestone points to the fact that such high readings had not happened in the last 2 to 4 million years. The only solution to change this rapidly growing, and eventually catastrophic, pattern is to slowly move away from fossil fuels burning in the next 50 to 100 years. 1
One of my initial goals in developing this unit was to make room for more Science in my classroom. As a self-contained fifth grade teacher, I find it very challenging to have the time, in an increasingly demanding daily schedule, to prepare hands-on materials and activities readily available for class. Tulsa Public Schools pacing calendar lists a unit on matter and energy that I inevitably simplify by studying states of water, kinetic and potential energy, and collaborating with parents in a hands-on unit about heat. However, with the headlines of May 10, I feel studying energy over time, more consistently and at a deeper level, is even of more capital importance to all educators and world citizens, especially children, adolescents and young adults. We are at a point in which we are creating a future we will depend upon for survival. However, the young generations are the ones to be most impacted by our understanding of the problems we face and the sustainable solutions we develop. It is, therefore, more imperative than ever to bring to our classes a clear understanding of energy as the source of survival for every civilization on Earth and, with that, the possibility of continual growth and development.
As an alternative to the diminishing blocks of sustained-teaching time in the classroom, I tend to develop interdisciplinary units. The logical integration of Science and Mathematics has allowed me to have one strong unit per semester. This present unit however, apart from Mathematics, will also have strong Language Arts (Reading/Writing) and History components and it is planned for 7-9 weeks. I will not be able to discuss those other subjects/themes in detail here but I will mention them briefly so that you can also find ways to lead students' understanding of the concepts across the disciplines –I have found that it is such recurrence, from different perspectives, that gives students the possibility of retaining and mastering the content.
From our district Science pacing guide and energy saving initiative, I am selecting two main specific themes for this unit: i) classification and transference of energy; and ii) energy conservation. These objectives are embedded in five process standards which according to Jon Muller are "statements that describe skills students should develop to enhance the process of learning." Our district incorporates all process standards in every one of the Science units: 1) Observation and Measurement; 2) Classification; 3) Experimentation; 4) Interpretation and Communication; and 5) Inquiry.
Division of the Unit
This unit will start with one background knowledge/summer activity, which opens and ends the unit. It will then progress into 3 sections, each one taking about two 45-minute blocks, and 1 last section which should take about three 45-minute blocks: 1) Energy: definition, sources and storage; 2) Fossil fuels; 3) The environment, pollution and global warming; and 4) Solar and Wind Power.
Energy: definition, sources and storage
Without energy nothing could be done; societies wouldn't have been able to survive and flourish; all the plant and animal kingdoms would not have had any chance of continued existence; the world would have gradually perished and the Earth would be another uninhabitable planet in the Milky Way. If these are hypothetical considerations of a past that did not happen, they can also turn out to be the nightmares of the future. The current debates about the amount of energy available to meet our needs, the security of the energy systems, and the impacts the extraction of some sources of energy have had, and will have, in the environment have been the object of closer looks and examination. 2
In the elementary school classroom, direct experience provides tangible notions for earlier conceptualizations of heat as a type of energy: in the summer, we have felt perspiration and learned to seek shade to avoid the heat. Our first ancestors most likely had similar experiences and once fire was conquered, and wood became the main fuel, this broad understanding of heat grew and made possible new experiences, like living in a cave and bringing fire, a new form of heat, inside. With fire domesticated and a home, new opportunities arose to see how objects changed from cold to hot, or vice versa, in the presence or absence of heat. Later on, heat was found to offer the possibility of transforming materials from raw to cooked, solid to liquid (and gas), as well as transforming rocks, creating art and protecting the body.
Next, work was added as in the classic example of rubbing sticks together to start a fire. However, it was also discovered how fatigue followed more arduous work: the more effort to push or pull was exerted, the more tired one felt; the logical conclusion was that there was a direct correlation between the force and the distance with the amount of work done. 3 Energy as the ability to do work is easily grasped from the scenarios above. And, doing work can also leave us without energy and the need for rest or food to replenish the system. Every animal knows biologically how to do these things, but we wonder little about how energy has been stored and is at hand to keep everything alive.
The main source of heat, and energy, is the Sun. Nuclear reactions, occurring at the core of it, in temperatures ranging from 5600?C to 6000?C, make possible that 70% of that energy, as electromagnetic radiation, be absorbed by the Earth, and the rest reflected back into the atmosphere. 4 The temperatures of the Earth depend on a fragile balance of this energy hitting our planet and the re-radiation of what is not absorbed into space.
The Sun's light or radiation plays an extra role in the creation of other types of energy. For instance, wind occurs when the Sun's unevenness in reaching the Earth allows pockets of cooler air to come in when heat starts rising. Parallel to this, a similar process happens in the oceans since they also get unequally heated by the Sun's rays; this irregularity, and the subsequent fluctuations of cooler and hotter air creates tremendous energetic power in the ocean currents.
A broader categorization of energy, as potential and kinetic, brings even other types into consideration. Potential or stored energy is subdivided into chemical, mechanical, nuclear and gravitational; kinetic or working energy is subdivided into radiant, thermal, motion, sound and electrical. In our vehicles, we can see many of these energies occurring or being transformed: we fill the tanks with fuel, commonly gasoline, which holds chemical energy and is transformed into heat when we start the car. Immediately, the mechanisms in the car allow heat, changed into gases, to increase and press onto pistons; this action creates mechanical energy which gives us the possibility of driving the car. In some situations, though, cars crash; and, occasionally, car pieces fly in the impacts. They fly because the potential energy in the unmoving parts of the vehicle changes into kinetic in the collision; at the same time, we can trace this kinetic energy back to the chemical energy in the gasoline that started the process.
And, what's the origin of the chemical energy in the gasoline? It comes from refined petroleum, extracted from deep reservoirs which, throughout millions of years, have been formed. Heat and pressure acted on decomposing trees, plants and grasses; as they were buried deep into the earth, their energy was kept in place. This energy was, at the same time, created thanks to sunlight in the process of photosynthesis. Thus, we return to the Sun as our main source of light and energy.
With the example of the car, we can see that energy cannot be created nor destroyed, only transformed. This natural occurring principle is known as the First Law of Thermodynamics or the Law of Conservation of Energy: "no new energy arises spontaneously and none is lost." 5 This is an important formulation: if the total amount of energy in the whole universe, and on the Earth, is consistent, it will then always end up somewhere, most likely in a different form. This acts as a guideline for decisions regarding energetic systems and their efficiency, as well as amounts that are lost as heat in the processes.
However, even though energy is constant, the sources may not be infinite. The Sun will certainly continue burning for millennia but, are all the sources we use capable of sustaining the continual, and growing, demand for energy? A further division sheds some light into this issue.
Renewable vs. nonrenewable sources of energy
The most prevalent use of energy is to power our cars, keep us warm in the winter and cool in the summer. The United States relies mostly on petroleum, natural gas, coal, propane and uranium to meet these needs. These are nonrenewable sources since they have been created over a long period of time and cannot be replenished as fast as our energy consumption continues and increases.
This has been known for a long time; the American, and world, governments, citizens and industries have tried to minimize the effects a lack of nonrenewable sources would have in our society by developing technologies that can harvest energy even closer to the inextinguishable sources. Biomass (organic matter, especially from plants), geothermal energy (internal heat from the earth), hydropower (energy of water), solar energy, and wind energy are all renewable sources.
Following the First Law of Thermodynamics, both renewables and nonrenewables can be converted into secondary energy sources. Two of these sources, commonly used, are electricity and hydrogen. They are considered rather transporters which store and distribute energy in accessible ways to be promptly used. However, both electricity and hydrogen cannot be harvested in site because they are created from other energy sources: firing coal helps create electricity, and most hydrogen comes from natural gas. In the laboratories, scientists are experimenting with the separation of the H 2O bond in water through a process called electrolysis.
Energy consumption in the United States
The use of renewable sources of energy has certainly grown in the last decade. However, technology advances are still trying to make the systems more affordable since, at the present time, they tend to be more expensive than some of the nonrenewables. At the same time, technological improvements have made it possible to be more efficient in the extraction of nonrenewables that were previously thought of as invaluable or too costly to produce. The newest nonrenewable sources of energy have expanded the market and seem in a trajectory to enlarge it even more. Some of these are categorized as "unconventional oil" since "their development depends on the advance of technology." 6 They include liquids that accompany the production of natural gas, oil sands, extra heavy oil, tight or shale oil, and oil shale. Production of natural gas has also grown to now encompass shale gas and methane hydrate, natural gas stored in ice. 7
The following chart summarizes the energy consumption of renewables and nonrenewables for the United States in 2011.
Source: U.S. Energy Information Administration, Monthly Energy Review March 2012 (Public Domain)
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