Introduction to Energy: Study with Video Lessons, Practice Problems & Examples

Energy, defined as the ability to perform work, exists in two main forms: potential energy, which is stored energy (e.g., gravitational and chemical potential energy), and kinetic energy, the energy of motion. In thermodynamics, the system refers to the matter being studied, while the surroundings encompass everything else. Biological systems, like plants, can exchange energy and mass with their surroundings, exemplified by photosynthesis, where solar energy and mass enter the system, producing glucose and oxygen as outputs.

Introduction to Energy

In this video, we're going to begin our introduction to energy. And so, energy is defined as the ability to perform work. And this term "work" can take on a lot of different meanings, but it's not referring to your homework in this sense. In biology specifically, work is referring to the transfer of energy that causes an overall change. And so, really, energy can be defined as the ability to perform an overall change in a living system.

Now, in our course, we're going to talk about two different types of energy: potential energy and kinetic energy. Potential energy is defined as energy that has potential. It is stored energy, and the stored energy is available to do work or to cause an overall change. Now, the second type of energy that you all should know is kinetic energy. And kinetic energy is the energy of motion.

So any substance that is moving or is in motion is going to have kinetic energy. And so let's take a look at our image down below to distinguish between these two types of energy. And so notice on the left-hand side over here, we have this little chart where we have the energy types in the left-hand column including potential energy, the storage form of energy, and kinetic energy, the energy of motion. And then we have examples of each of these types of energy. And so let's start off with the potential energy here.

There are different types of potential energy. There are different ways to store energy. So one example of potential energy that is stored is gravitational potential energy. And so gravitational potential energy is when something is quite high with respect to something that has gravity. And so for example, a biker that is on the top of a hill, like this biker here which is on the top of a hill, this image of the biker that you see here on the left is really just a screenshot of this image of the biker over here on the right.

So a biker that's at the top of a hill is not moving, but it still has high gravitational potential energy. Now another type of potential energy, of stored energy, is chemical potential energy. And chemical potential energy is when energy is stored in chemical bonds. And a classic example of a molecule that has chemical potential energy is glucose, which is the most abundant and the most common sugar that exists. Now in terms of kinetic energy, the energy of motion, really all moving objects are going to have kinetic energy, including a biker that is actually coasting or moving really, really fast is going to have kinetic energy.

But also, muscle contractions are a form of kinetic energy. So when you flex your bicep or get up to go get a glass of water, those muscle contractions are considered a type of kinetic energy. Now, let's take a look at this image over here on the right-hand side, which is also helping to distinguish between potential and kinetic energy. And so once again, a biker that's at the top of a hill, even though they're not moving whatsoever at the top of the hill, is going to have quite high gravitational potential energy. But as soon as this biker makes a dip in this direction, it's going to start coasting down the hill, moving really, really fast down the hill because gravity is acting on the biker.

And so the biker, when it is moving, is going to have kinetic energy. And so the potential energy is going to be converted into kinetic energy as soon as the biker starts to move. And then when the biker makes it to the bottom of the hill, the biker is going to have low gravitational potential energy because the biker is no longer at the top of the hill. And so this here concludes our introduction to the two main types of energy that we're going to talk about moving forward, potential energy and kinetic energy. And so we'll be able to get some practice in our next couple of videos.

So I'll see you guys there.

Which of the following is an example of potential energy?

• A. Water rushing over a water fall.
• B. A glucose molecule.
• C. A spring being released and expanding rapidly.
• D. An ant foraging (moving around) for food.

Which of the following is NOT a form of kinetic energy?

• A. When the temperature of a substance rises causing the molecules of that substance to move faster.
• B. When a hockey puck slides across the ice after being hit by a player.
• C. When glucose molecules are broken down to create energy for cellular work.
• D. When the molecules of the air vibrate transmitting soundwaves.

Thermodynamics: System vs. Surroundings

In this video, we're going to introduce thermodynamics and distinguish between the system and the surroundings. Thermodynamics is the study of energy transfers between different bodies of matter. It is really important in the study of thermodynamics to distinguish between the system and the surroundings. The system is defined as the specific portion of matter that's being studied, and depending on the scenario, the system can change quite drastically.

In some scenarios, the system will be an entire living organism, and in other scenarios, it will be just a single specific reaction. The system is any specific portion of matter that is the main focus of the study. Then, of course, the surroundings are essentially everything else on the outside of the system—part of the surroundings. Now, biological systems are very interesting because they transfer both energy and mass with the surroundings.

Let's take a look at our image below to clear up this idea. In this particular scenario, the biological system is this plant we have here in the middle. Notice that the biological system, this plant, is capable of allowing energy to enter the system but it's also capable of allowing mass to enter the system. You can see that solar energy from the sun is entering the biological system, entering into the plant. But also, components that have mass, such as carbon dioxide gas and water molecules, are also capable of entering the biological system.

On the other end, it's important to note that not only can energy and mass enter the system, but they can also exit the system as well. You can see that energy is capable of entering the system and then also exiting the system in a different form. Mass is also capable of entering the system and also exiting the system in a different form. This biological system is a plant and is capable of performing photosynthesis, and that's really what we're showing you here on this page. We’ll talk a lot more about photosynthesis later in our course.

What you can see here is that solar energy, and mass such as carbon dioxide and water, are capable of entering the biological system, and then what ends up coming out of the biological system is glucose which is a common form of chemical potential energy because all these bonds that are formed in glucose contain chemical potential energy. It's a form of energy that's exiting the system here. Also, oxygen gas is a form of mass that's exiting the system. The main takeaway here is that biological systems are capable of allowing energy and mass to enter the system, but also, energy and mass can also exit. Distinguishing between the system and the surroundings will allow us to get some practice applying these concepts as we move forward in our course. So, I'll see you all in our next video.

Why are the principles of thermodynamics important for the study of biology?

• A. The principles of thermodynamics govern the chemical processes in all biological organisms.
• B. The principles of thermodynamics govern how an organism exchanges energy with their environment.
• C. The principles of thermodynamics govern how all life on Earth exchanges energy.
• D. All of the above.

Which of the following is NOT an example of a biological system?

• A. A human eating a cheeseburger.
• B. A coral reef where energy and mass both enter and exit.
• C. The digestive system of an organism absorbing food energy and discarding food waste.
• D. The universe where the amount of energy and mass is constant.

Here’s what students ask on this topic:

What is the difference between potential energy and kinetic energy?

Potential energy is stored energy that has the potential to do work or cause change. Examples include gravitational potential energy, like a biker at the top of a hill, and chemical potential energy, such as the energy stored in glucose molecules. Kinetic energy, on the other hand, is the energy of motion. Any moving object, like a biker coasting down a hill or muscle contractions, possesses kinetic energy. Essentially, potential energy can be converted into kinetic energy when the stored energy is put into motion.

How do biological systems exchange energy and mass with their surroundings?

Biological systems, such as plants, can exchange both energy and mass with their surroundings. For example, during photosynthesis, a plant absorbs solar energy and takes in carbon dioxide (CO₂) and water (H₂O). These inputs are converted into glucose, which stores chemical potential energy, and oxygen (O₂). Thus, energy and mass enter the system in the form of sunlight, CO₂, and H₂O, and exit as glucose and O₂.

What is thermodynamics and how does it relate to biological systems?

Thermodynamics is the study of energy transfers between different bodies of matter. In biological systems, thermodynamics helps us understand how energy and mass are exchanged between the system (e.g., a plant) and its surroundings. For instance, during photosynthesis, a plant absorbs solar energy and converts it into chemical potential energy stored in glucose, while also releasing oxygen. This illustrates how biological systems follow the principles of thermodynamics by transferring energy and mass.

What are some examples of potential energy in biological systems?

In biological systems, potential energy can be found in various forms. Gravitational potential energy is seen in objects positioned at a height, like a biker at the top of a hill. Chemical potential energy is stored in the bonds of molecules, such as glucose, which is a common energy source in living organisms. These forms of potential energy can be converted into kinetic energy to perform work or cause changes within the system.

How does the concept of a system and surroundings apply to energy transfer in biology?

In biology, the system refers to the specific portion of matter being studied, such as a plant, while the surroundings encompass everything else. Energy and mass can be transferred between the system and its surroundings. For example, in photosynthesis, a plant (the system) absorbs solar energy and takes in carbon dioxide and water from its surroundings. These inputs are converted into glucose and oxygen, which are then released back into the surroundings, demonstrating the exchange of energy and mass.