The term “chemical energy” can bring many things to mind, but the main question is what is it? Well, chemical energy is what allows our bodies to keep functioning, electricity to be produced, and so on. In more basic terms, we, along with every living thing on this planet, need chemical energy to survive.
Chemical energy is a potential energy source, stored in the atoms, electrons, and molecular bonds that make up the world around us. From here, it undergoes several processes and chemical reactions in order to release energy.
This naturally leads into some questions: What forms does this take, how can we measure it, and what do we use it for? Let’s go over some examples to help you better understand just what goes into this vital part of chemistry.
In this post:
How Many Different Types of Chemical Energy Are There?
When it comes to chemical energy, anything that can be considered a fuel source contains it. This means there are near countless kinds of chemical energy out there, but here are a few examples:
- Photosynthesis – Where solar energy is changed into chemical energy
- Chemical batteries – Chemical compositions within allow for energy to be stored and then converted to electricity
- Fuel burning – Coal, wood, petroleum, biomass, and any other flammable fuel source can be burned to release chemical energy into heat and light
Key Takeaways
Chemical energy is a type of potential energy stored in atoms, electrons, and molecular bonds
Energy is released when these bonds are broken, usually through exothermic reactions like combustion or metabolism
Chemical energy is found in processes like photosynthesis, as well as in sources like food, fuels, and batteries
Its quantity is determined by calculating the energy difference between the reactants and products during a reaction
Where Can You Find Chemical Energy?
Chemical energy can be found in two key locations on a molecular and atomic level:
- Inside the atom
Chemical energy is stored in the bonds that make up chemical compounds. This means that chemical energy is commonly contained within the atoms and molecules inside every living organism. When stored in this way, energy can be classified into two categories: nuclear energy and chemical energy.
Nuclear energy is released when nuclei are either split, or fused in the forms of electromagnetic radiation, including gamma rays, heat, and subatomic particles. These aren’t examples of chemical energy as they’re generated through nuclear decay or nuclear reactions. Chemical energy is released when molecular bonds break, or when they form during a usually exothermic reaction.
Another difference is that while our bodies, and indeed all living organisms, need chemical energy to survive, we make no use of the nuclear energy or nuclear processes taking place inside our atomic nuclei.

- Energy levels and electrons
Chemical reactions that release energy are usually exothermic, i.e. they release heat. These reactions can also release energy in the form of light, and even sound. This process involves the movements of electrons from lower energy levels to higher energy levels, then back again.
The amount of chemical energy released in these contexts is directly proportional to the speed of the reaction. Reactivity is correlated with how the electrons are arranged on different energy levels or shells.
For instance, when oxygen reacts with hydrogen, it’s fast and explosive with a large amount of heat, light, and sound energy released almost instantly. By comparison, when oxygen reacts with iron, which is also known as rusting, the process is slow and barely noticeable. In this example, energy is released over a longer period of time.
- Molecular bonds
Chemical energy is basically stored energy in molecular bonds. It can either be abruptly released, such as when oxygen reacts with hydrogen, or it can be gradually and methodically released, such as in metabolic processes in the body.
The latter explains why chemical energy is also found in food, specifically within its molecular bonds. The organic constituents of organisms, such as the proteins in the muscles and the glucose, or fructose in fruits, are sources of chemical energy.
How Is Chemical Energy Measured?
Before we can understand how chemical energy is measured, we first need to define energy. The simplest and classic definition of energy in physics is ‘the capacity to do work.’ This means that a certain amount of energy needs to be transferred or converted in order to accomplish something.
- The basic formula for energy
‘Work’ is defined as the product of force and distance. This implies motion and mass, since force is simply the product of mass and acceleration. Therefore, work is just an application of energy. For example, the chemical energy of a battery can be used to move mass or accelerate mass across distances through the use of a motor.
This is the basis for the mechanical measurement of chemical energy. The basic formula for energy is one half the mass multiplied by the square of the velocity. It can also be expressed in terms of power multiplied by time, such as kilowatt-hour.
The basic mechanical formula for energy has many derivations, but it all boils down to the motion of mass. For example, the heat of boiling water is actually particles of water moving rapidly because of high amounts of energy. The same is true for any hot object – as another example, radiation energy is simply the product of the motions of excited particles.
- Units of measurements
The standard metric system or SI unit of measure for energy is joules (J). This is equivalent to one Newton of force acting through one metre distance, and can be converted into other measurements of energy such as calories.
As an example, one calorie is the amount of energy needed to raise the temperature of 1g of water by 1°C, which is the equivalent to 4.184 J. Similarly, a BTU (British Thermal Unit) is the amount of energy needed to raise one pound of water by 1°F.
Most chemical reactions are exothermic and give off heat, which is why the example uses the raising of temperature. However, endothermic chemical reactions still involve energy. In this context, instead of releasing energy, one of the reactants absorbs energy.
The temperature differential in an endothermic reaction is still measurable using the standard formula and unit of measurements used to calculate the energy released from exothermic reactions.
How Is Chemical Energy Released?
The chemical energy produced during a reaction is released in several ways, depending on the reactants involved. While it can be produced as light, chemical energy is usually released in the form of heat.
In the body, the main way chemical energy is released is through metabolic processes, specifically catabolism. This allows cells to release stored energy by breaking down the molecular bonds in food. In this context, the reaction is exothermic, and the chemical energy is released to allow the body to function.
Outside of the body, chemical energy is released in a similar way: a chemical reaction causes the bonds in compounds to break, releasing energy.
In the same way that the body converts it into mechanical energy (which basically allows us to move and operate), chemical energy can be converted into many forms of energy, depending on where it’s released from. For example, when contained in coal, chemical energy can be converted into electrical energy.
How To Calculate Chemical Energy
As previously mentioned, chemical reactions can either release (exothermic) or absorb (endothermic) energy. During a chemical reaction, the molecular bonds of the constituent elements or chemical groups in compounds are broken, and new bonds are formed.
Calculating the chemical energy in a reaction simply involves subtracting the energy of the products from the energy of the reactants. The difference is either released or absorbed as heat. If the energy of the products is greater than the energy of the reactants, heat is absorbed. If the energy of the products is lesser than the energy of the reactants, heat is released.
Theoretically, the type of reaction can actually be predicted, whether it is endothermic or exothermic. However, the precise amount of energy must still be experimentally determined through chemical testing and other processes.

What is Potential Chemical Energy?
Potential chemical energy is another term you sometimes see used interchangeably with chemical energy.
Potential chemical energy is the stored energy that the chemical reaction will release, and is determined by the strength and arrangement of the component bonds. In general, it acts as a good term to use for defining what the output of a reaction could be.
Here’s some other examples to consider:
Examples of Chemical Energy
Chemical energy powers diverse processes in our world. It’s used by almost all life-supporting functions, from respiration and metabolism to photosynthesis. To put it simply, every living thing needs chemical energy in order to survive, whether this is consumed from organic food or inorganic compounds.
But chemical energy isn’t just used inside the body. In fact, humanity’s largest use of energy to date is fossil fuel, which is used to power industries, transportation, and electricity. Batteries are another common source of chemical energy, and they convert this into electrical energy that is then stored away for later use.
Fire As Chemical Energy
Fire is the result of a rapid reaction between oxygen and combustible materials. When things like wood or coal burn, they combust with oxygen, creating CO2 and H2O in the process.
This reaction breaks molecular bonds, releasing stored chemical energy as heat and light. These are two prominent examples of how chemical energy changes into other forms.
Petroleum As Chemical Energy
Petroleum is a flammable liquid, able to release energy when burnt. Much like fire, this. It can also be converted into other forms of chemical energy storage, such as gasoline.
Petroleum stores chemical energy in its hydrocarbon molecules. When refined and burned it can be used to generate electricity, power cars, and heat homes.
This versatility makes petroleum a cornerstone of modern energy systems, despite environmental challenges associated with its use.
Food As Chemical Energy
Food is an essential source of chemical energy for living beings. Its energy is stored in molecular bonds of nutrients like proteins and fats.
Through digestion and cellular respiration, these molecules are broken down, releasing energy that supports growth, movement, and other vital functions.
Conclusion
Chemical energy is an indispensable force that drives life and technology. Found in everything from the food we eat to the fuels we burn, its ability to transform into various energy forms underpins countless aspects of life we take for granted.
While there are challenges to overcome with some common sources of chemical energy, understanding the measurement and applications, helps us better appreciate and make use of this vital energy form for sustainable progress.