 # In physics, energy is the property that must be transferred to an object in order to perform work on, or to heat, the object. Energy is a conserved quantity; the SI unit of energy is the joule (J). Energy can be transformed, not created or destroyed. The laws of thermodynamics state that energy can be transformed from one form to another, but it is not possible to create or destroy it. The total energy of a system can be calculated by adding up all forms of energy in the system. The total energy of a system is sometimes called its "energy content". Different forms of energy can be transformed into one another, but it is not possible to create or destroy energy.

#### Topics

No Related Subtopics

### Discussion

You must be signed in to discuss.
##### Top Educators  ##### Stephanie C.

University of Central Florida ##### Allea C.

University of Maryland - University College ### Recommended Quiz

#### Chemistry 101

Create your own quiz or take a quiz that has been automatically generated based on what you have been learning. Expose yourself to new questions and test your abilities with different levels of difficulty.

### Video Transcript

all molecules have energy, which can be understood in terms of potential energy and kinetic energy. So if you take a molecule that we're all familiar with, like water, we'll see that water is composed of an oxygen atom bonded to two hydrogen atoms. So each bond in this molecule has a potential energy that is dependent both on the mass of the atoms as well as the bond string where the stronger the bond, um, the higher the potential energy is. So this is one form of energy that a molecule has, and another one is connect energy. So instead of this line structure, I'll be writing the chemical formula instead. So it's easier to treat this as one whole molecule. So if you imagine this one molecule in space, we can see that it can move in any direction that it wants to in three dimensional space, Um, at any speed. So anything that has both mhm mass and a speed, um, which is also velocity, also has a kinetic energy. So again, energy can be understood in these two types of energies, potential energy and kinetic energy. Which one is associate ID with how the molecule is structured as well as how the molecules can move in space. So energy is an important concept because it helps us understand the likelihood of a reaction occurring between molecules and specifically, what bonds are broken or formed during these reactions, as well as phase changes. Reactions follow the first law of thermodynamics, which is basically that energy is conserved or energy cannot be created or destroyed. And this could be better understood or summarize. Um, by this formula, you is equal to W plus Q. Where you represents energy and W represents work and Q represents. Heat and energy is transferred through work or heat. Reactions can also be a new thermic or academic, and an end with thermic reaction absorbs heat. Instead of writing heat, I'll abbreviate this as a triangle on an exit there, make reaction, will release heat other concepts such as entropy and gives free energy. Also help us understand reactions even further by telling us what direction a reaction will occur, which is what entropy will give us information about as well as thesis on tin 80 of reaction or, in other words, does it take energy toe happen, and this is associate it with the Gibbs Free Energy Brown University
##### Top Chemistry 101 Educators  ##### Stephanie C.

University of Central Florida ##### Allea C.

University of Maryland - University College 