Learning Objectives Self-Check
Read through the following statements/questions. You should be able to answer all of these after reading through the content on this page. After going through the content, check the boxes next to the questions/statements that you feel at least somewhat confident answering. I suggest writing or typing out your answers, but if nothing else, say them out loud to yourself. This is to help you reflect on important content and will help you prepare for this week's quiz. It will also help lay the foundation for future course content.
Considering that this course is called “Energy and Sustainability in Contemporary Culture,” let’s start by answering two fundamental questions:
- What is energy?
- What is sustainability?
Let’s tackle the second question first, since the answer is a little more straightforward, even if it’s not always easy to grasp: What, exactly, is energy?
To Read Now
The National Energy Education Development (NEED) Project is a non-profit organization that provides a lot of useful (and free!) information about energy and energy issues. Please read the first two pages of their Introduction to Energy, which provides a good overview of energy. Hopefully, much of this will be a review for you! (Note that we will go over more up-to-date energy use data than the document has - i.e., more recent than 2009 - below.). You are welcome to read the rest, but it is not necessary. (It is helpful, though.)
- Introduction to Energy, National Energy Education Development Project (pp. 8 - 9)
Energy is most commonly defined as "the ability to do work." This is a useful technical definition, but from a practical perspective, the NEED Project's indication that energy is also "the ability to produce change" is helpful. A similar way to think of energy is that it "makes things happen." Energy is required to make a TV turn on, a car to move, the sun to generate light and heat, water to vaporize, plants to add biomass, a power plant to generate electricity, and for you to think about this course content as you read it. And even if these things are not actually happening, energy provides the ability to make them happen.
As indicated in the reading, the two categories of energy are potential (stored energy) and kinetic (energy in motion), each of which have several forms. (Note that the categories are listed in parentheses below because they can either be included or not, e.g., chemical energy can be referred to as "chemical" or "chemical potential" energy. Generally, "kinetic" or "potential" is not included.):
- Chemical (potential) energy is stored in the bonds between atoms and molecules. Common examples include the energy stored in food, fossil fuels, and batteries, but anything that is made of more than one atom has chemical energy. Practically speaking, basically everything made of matter has chemical energy.
- Mechanical (potential) energy is "stored in objects by the application of a force." Common examples include a wound spring, a stretched-out rubber band, and compressed air.
- Nuclear (potential) energy is "stored in the nucleus of atoms," and is what holds the nucleus together. Anything made of matter has nuclear energy, but most of the nuclear energy converted by humans comes from the fission (splitting) of uranium atoms and is used to generate electricity. Most of the energy used by humans, however, comes from nuclear fusion (fusing of atoms) in the sun.
- Gravitational (potential) energy is "energy of position or place." Common examples include water (e.g., in a river) at a high(er) elevation, a ball sitting on top of a hill, and you sitting on your chair right now. If you see naturally flowing water, it is moving down hill (tides and waves notwithstanding), so hydroelectric energy (electrical energy generated from flowing water) starts out as gravitational potential energy.
- Electrical (kinetic) energy is "the movement of electrons." The most common example of this is electricity moving through a wire, but discharging static electricity and lightning are also electrical energy.
- Radiant (kinetic) energy is also called "electromagnetic energy." It travels in transverse waves and is produced by anything with a temperature above absolute zero. Common examples include light, sunlight, microwaves, radio waves, and radiant heat emanating in all directions from a fire.
- Thermal (kinetic) energy is the vibration of the molecules of a substance. As an object or substance gets heated up, the molecules vibrate more rapidly, and they slow down as it cools down. Humans cannot see this vibration because it happens at a molecular level, but we can feel it, or at least the results of it. Have you ever accidentally touched a hot stove and gotten burned? That unpleasant sensation is the result of the quickly vibrating molecules of the stove imparting their thermal energy into your skin. Anything above absolute zero has thermal energy, so it is all around us all the time, including everything you see right now.
- Motion (kinetic) energy is the energy in moving objects. Anything with mass that is moving has motion energy. Moving cars, flowing water, a falling object, and even wind (air is made of matter, after all!) are common examples.
- Sound (kinetic) energy moves in waves and is produced by vibrating objects. When you hear something, it is the result of the bones in your ear absorbing and converting these waves into motion energy, which your brain then interprets as sound. Despite what you may have heard, if a tree falls in the woods and there is no one there to hear it, it does generate a sound! Well, it generates sound energy, at least.
Energy efficiency and conservation of energy will be addressed later in this lesson.
The gentleman in this video (4:35 long) also provides useful information regarding energy and illustrates many of the concepts from the reading above. (In case you are wondering, yes, he is this excited all the time. He also has a number of really good videos regarding many topics. His YouTube channel has over 6,000,000 subscribers, so he must be doing something right!). Please note that you can open this video in YouTube by clicking on the title of the video in the window below.
Okay, so if you ask a physicist or energy expert what energy is, she will likely tell you that energy is the ability to do work. This sounds straightforward enough, but you may be thinking, “what is work?” Ask the same (or another) expert, and you will likely hear: “Work is the transfer of energy.” The video below from Kahn Academy (3:16) is optional but does a good job of explaining what this means. If you are still a little confused after watching it, you may want to read through the rest of the energy lesson, then go back to it. The formulas are not important for this course, but the concept of how work is related to energy is important. One thing to note: the narrator uses the term "Joule" a lot in this video. A Joule (J) is the international unit of energy and is simply a way to quantify energy. (More on quantifying energy shortly!)
Work as the transfer of energy from the Khan Academy (3:17 minutes)
In order for an object to gain or lose energy, work must happen. If you pick up a book from the ground and put it on a table, the book gained gravitational (potential) energy. You performed work on the book, and the amount of work is equal to the amount of potential energy gained. When you pull your car or bike out from a parking spot, the car/bike has motion energy, but when it was parked had none. That energy gain is the result of work done by the car engine (then drivetrain and wheels) or your legs (then pedals, chain, and wheels), and you can figure out the work done by considering the velocity and mass of the moving object. When the vehicle stops, the bike/car performs work on the road and tires, resulting in them heating up.
The sun is constantly generating massive amounts of radiant energy. That energy is provided by hydrogen atoms fusing together into helium and releasing nuclear energy. The amount of radiant energy generated in this process is equal to the amount of work done by the hydrogen atoms on the sun. When this sunlight hits your skin (or any object), it performs work on it, resulting in a gain in thermal energy. This gain in thermal energy is equal to the amount of work done.
I could go on and on, but the key thing to remember is that energy transfer requires work. Any time energy is transferred from place to place or from one form to another, work must be done, and the amount of work is equal to the amount of energy gained or lost.
Optional (But Strongly Suggested)
Now that you have completed the content, I suggest going through the Learning Objectives Self-Check list at the top of the page.