How Do We Use Chemicals To Create Energy?

Chemicals and energy are fundamentally linked. Chemicals contain stored potential energy that can be converted into other useful forms of energy through chemical reactions. From the food we eat to the gasoline that powers cars, chemicals provide the fuel that drives life and modern society. This article explores the various ways we utilize chemical reactions to extract energy for human use.

Chemicals are substances composed of different elements and molecules. They contain energy stored in the arrangement of their molecular bonds. Energy is the ability to do work or produce change, such as motion, light, or heat. There are many forms of energy, including chemical, electrical, radiant, nuclear, mechanical, thermal, and more. Chemical energy refers specifically to the potential energy stored in the bonds between a chemical’s atoms and molecules. This energy can be released or transformed during chemical reactions.

We rely on chemical energy conversions in many aspects of daily life. Our bodies convert the chemical energy in food into thermal and mechanical energy through metabolic processes. Engines combust the chemical energy in fuels like gasoline to release heat and propel vehicles. Batteries use electrochemical reactions to produce electricity to power devices. On an industrial scale, chemical energy is harnessed for transportation, electricity generation, manufacturing, and more. This article will provide an overview of the key ways we utilize chemical reactions and conversions to extract useful energy.


Plants use a process called photosynthesis to create their own chemical energy from sunlight, water and carbon dioxide. This process takes place in plant cells that contain chlorophyll, a green pigment that can absorb sunlight.

During photosynthesis, chlorophyll captures photons from sunlight and uses their energy to split water molecules into hydrogen and oxygen. The hydrogen joins with carbon dioxide to produce glucose, a simple sugar. Oxygen is released as a byproduct of photosynthesis.

The overall chemical reaction looks like this:

6CO2 + 6H2O + sunlight energy -> C6H12O6 + 6O2

This equation shows how six molecules of carbon dioxide (CO2) and six molecules of water (H2O) react with solar energy to produce one molecule of glucose (C6H12O6) and six molecules of oxygen (O2). The glucose sugars produced by photosynthesis provide chemical energy that powers plant growth and metabolism.

Cellular Respiration

Cellular respiration is the process cells use to break down carbohydrates and produce energy in the form of ATP. This process takes place in the mitochondria of cells. Mitochondria act as the “powerhouses” of cells by converting energy from food into a usable form.

During cellular respiration, cells break down glucose molecules from carbohydrates in a series of chemical reactions. The glucose molecules are broken down step-by-step, which releases energy that is used to make ATP. Oxygen is required for cellular respiration, allowing the mitochondria to undergo aerobic (with oxygen) respiration.

The overall chemical formula for cellular respiration is:

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP)

Glucose (C6H12O6) and oxygen (O2) enter the mitochondria and undergo a series of reactions. This produces carbon dioxide (CO2), water (H2O), and energy in the form of ATP.

So in summary, cellular respiration allows cells to harvest energy from food to produce ATP. This essential process takes place in the mitochondria, uses oxygen, and produces CO2 and water as byproducts. The energy released allows cells to carry out their functions and keep the organism alive.


Burning hydrocarbons with oxygen releases energy in the form of heat. This process is called combustion. Hydrocarbons refer to compounds that consist of hydrogen and carbon atoms, such as fuels like wood, coal, natural gas, and gasoline.

When these fuels are burned with oxygen, the carbon and hydrogen react with the oxygen molecules, breaking apart the bonds holding these compounds together. New bonds are formed between the atoms, creating carbon dioxide and water as byproducts. However, these new bonds release less energy than it took to break the original bonds in the fuel source. This net release of energy is what provides the heat and power from combustion.

a diagram showing the combustion reaction of a hydrocarbon fuel and oxygen to produce carbon dioxide, water, and energy.

The general combustion reaction looks like this:

Fuel (hydrocarbon) + Oxygen → Carbon Dioxide + Water + Energy

The amount of energy released depends on the specific fuel source. But in all cases, the chemical reaction of burning a hydrocarbon fuel with oxygen reliably produces a substantial amount of energy that can be harnessed for human use.


Batteries produce electricity through oxidation-reduction reactions. These reactions involve the transfer of electrons between two electrodes, the anode and cathode, which are separated by an electrolyte. The anode undergoes oxidation, giving up electrons, while the cathode undergoes reduction, gaining electrons. This electron flow produces an electric current that can be used to power devices.

In a battery, the anode is the negative electrode and is made from materials that readily give up electrons, like zinc or lithium. The cathode is the positive electrode and is made from materials that readily accept electrons, like manganese dioxide or nickel oxide. The electrolyte allows ions, but not electrons, to flow between the electrodes to balance the flow of electrons in the external circuit. Common electrolytes include aqueous acids or alkaline solutions.

Some common battery types and their electrode materials include:

  • Alkaline batteries – Zinc (anode) and manganese dioxide (cathode)
  • Lithium-ion batteries – Lithium cobalt oxide (cathode) and graphite (anode)
  • Lead-acid batteries – Lead (anode) and lead dioxide (cathode)
  • Nickel-metal hydride batteries – Nickel oxide hydroxide (cathode) and hydrogen-absorbing alloy (anode)

Choosing appropriate electrode materials and electrolytes is key to optimizing the voltage, capacity, energy density, and safety of a battery for its intended application.

Fuel Cells

Fuel cells generate electricity through a chemical reaction known as oxidation. An oxidizing agent, often oxygen from the air, combines with the fuel, typically hydrogen, in the presence of a catalyst. The oxidation of the fuel produces electricity and water or other harmless byproducts.

Unlike batteries, fuel cells do not need to be periodically recharged. As long as fuel and oxidant are supplied, the fuel cells continue to produce electricity. Fuel cells are very efficient at converting chemical energy into electrical energy.

One of the most common types of fuel cells uses hydrogen gas as the fuel and oxygen gas as the oxidant. These hydrogen fuel cells offer a clean and efficient way to produce electricity, with water as the only byproduct. Hydrogen fuel cells have potential applications in vehicles, buildings, and portable electronics.


Biofuels are liquid fuels made from biomass – organic matter such as plants or waste. The two most common types of biofuels are ethanol and biodiesel.

Ethanol is an alcohol fuel made by fermenting the sugars in crops like corn, sugarcane or switchgrass. It can be blended with gasoline to reduce petroleum use. Ethanol makes up 10% of the gasoline sold in the U.S. today.

Biodiesel is made by combining oils like soybean oil with alcohol through a chemical process called transesterification. It can replace petroleum-based diesel in vehicles. Biodiesel is commonly blended with conventional diesel fuel.

Biofuels can also be made from algae. Algae can produce oil and can be grown rapidly since it requires less land and water than most crops. Algae biofuel is still in early research and development stages.

Because biofuels come from renewable plant materials, they can replace fossil fuels which are non-renewable. Widespread use of biofuels could reduce dependence on finite resources like oil while creating economic opportunities in agriculture and renewable energy.

Fossil Fuels

Fossil fuels such as oil, natural gas, and coal are formed over millions of years from the remains of ancient plants and animals. These fuels are classified as nonrenewable energy sources because they take millions of years to form, and reserves are being depleted much faster than new ones are being made.

The fossil fuels we use today started forming during the Carboniferous Period over 300 million years ago, when land plants became abundant. As plants died and got buried by sediments, heat and pressure turned them into fossil fuels over time. Ancient fossilized zooplankton and algae also became petroleum.

Fossils fuels are hydrocarbons, primarily containing hydrogen and carbon atoms. When they burn, the chemical energy is released and converted to thermal energy that can be harnessed for power. Since fossil fuels require such a long time to form, and consumption rates are high, they are not considered sustainable resources for long-term energy needs.

Nuclear Energy

Nuclear energy utilizes the energy released during nuclear fission or fusion reactions of atomic nuclei. In nuclear fission, atoms like uranium or plutonium are split into smaller atoms, releasing a large amount of energy in the process. Fission takes place inside nuclear reactors, where uranium fuel rods are bombarded with neutrons, causing them to split apart. The released energy heats water into steam, which spins a turbine to generate electricity.

Nuclear fusion works by fusing together light atoms like hydrogen into heavier ones like helium. This releases even more energy than fission. Fusion occurs naturally in stars like the sun, but scientists are working on developing fusion reactors to harness this energy source on Earth.

While nuclear power does not produce air pollution or carbon emissions while generating electricity, it does produce radioactive waste. This waste must be contained and isolated from the environment for thousands of years while its radiation dissipates. Developing safe long-term storage solutions for nuclear waste is an important challenge facing the industry.


From our discussion, it’s clear that chemicals can be converted to energy in a number of different ways, from the small scale to the large scale. At a cellular level, photosynthesis and cellular respiration convert chemical energy to sustain life. On an industrial level, we harness chemical energy by burning fossil fuels, through nuclear fission, and in batteries and fuel cells. While these chemical-to-energy conversions provide us with power, heat, electricity, and mobility, they often produce waste byproducts. As our energy needs grow, it will be critical to develop cleaner methods of chemical energy conversion that minimize pollution. Emerging technologies like biofuels show promise if production can be scaled sustainably. With continued research into nuclear fusion, fuel cells, and renewable energy like solar and wind, our chemical-to-energy processes may one day be emissions-free. For now, being mindful of our energy usage and investigating cleaner energy alternatives will lead us closer to that future.

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