What is Energy ?

what is energy

What is Energy?

Energy is simply how things move and change. It’s versatile and can exist in multiple forms and serve different purposes. In its simplest form, energy is the ability to do work.

But its definition may vary depending on the context or area of application. So, what is energy in science? Energy in physics, for instance, is the capacity to do work. It exists in multiple forms including:

  • Kinetic
  • Chemical
  • Potential
  • Electrical
  • Thermal
  • Nuclear

In chemistry’s context, energy can be described as an attribute of a substance as a result of aggregate, atomic, and molecular structure.

How is Energy Measured?

Energy is measured in Joule (J). Named after the English physicist James Prescott Joule (1818 – 1889), who discovered the relationship between heat and mechanical work, this later led to the evolution of the laws of thermodynamics. However, there still other units that are commonly used to measure it. The most common one is kilowatt/hour which’s used to calculate electricity bills.

What is the difference between Energy and Power?

Energy makes things move or change and it normally takes different forms. It makes a change happen and it can be transferred from one object to the next. On the other hand, power is the rate of energy transfer.

While both power and energy are closely related, they are not the same in terms of the physical quantity. That’s why energy is measured in Joules and Power in watts.

What is Energy in Science?

Let us now look at each form and type of energy, plus their uses individually in order to get a better understanding of the roles they play relating to energy in science.

What is Energy of Activation?

Energy Activation in chemistry is the minimum amount of energy that’s needed to activate molecules or atoms in a condition that they will undergo physical transportation or chemical transformation.

It should be noted that if the activation energy is high, then the chemical reaction will be quite slow. This usually happens because the molecules or atoms can only complete a reaction fully once they reach the top of the energy activation barrier.

 Types of Energy

There are several forms of energy but they can be categorized into different forms: potential and kinetic. Kinetic is a type of energy that’s found in moving objects. On the other hand, potential energy is energy that’s found in objects in stationary positions. It’s a stored type of energy.

So, what types of energy is there?

Thermal or Heat Energy

Thermal energy is found in a substance whose atoms and molecules are simply vibrating faster as a result of a rise in temperature. The atoms and molecules usually collide with each other during rapid movements. This makes it a kinetic type of energy.

Matter consists of atoms and molecules that are constantly moving. When there is an increase in temperature, they move faster and end up bumping into each other, leading to the production of heat or thermal energy. Note that the more there are rapid movements in the molecules or atoms, the higher the heat energy.

Examples of thermal energy include:

  • The solar energy that heats the atmosphere through radiation
  • Energy from fuel cells
  • Melting ice
  • A hot cup of coffee or tea
  • The heat from the oceans
  • Geothermal energy

Types of thermal energy transfer

There are three ways in which thermal energy is transferred:

  • Radiation- the transfer involves the use of electromagnetic waves. Radiation energy can travel through space as well as other mediums.
  • Convection – it involves thermal energy transfer through a fluid such as liquid or air. When the fluid particles are heated up, they become less dense and move up while the colder particles move down, creating what’s known as convection currents.
  • Conduction- the thermal energy we transferred through collisions of neighboring molecules and atoms. This process usually occurs in solid and liquid items since the particles are closer together. Conduction doesn’t occur in gases since the particles are far apart.

Chemical Energy

It’s normally stored in the chemical bonds of compounds. This type of energy may be released during the process of chemical reaction that’s caused by heat. Well, such chemical reactions are known as exothermic reactions.

When we consume food, the chemical energy in it is usually converted into heat and mechanical energy by the body. Chemical energy is a type of potential energy since it’s normally stored. It’s crucial for the existence of human beings as well as the natural world, especially plants.

Examples of chemical energy include:

  • Food that’s digested to produce energy used by body cells.
  • Chemical batteries storing chemical energy that can be converted into electric power.
  • Coal and wood energy undergoing combustion to produce heat and light.
  • Petroleum energy getting burned to convert chemical energy to heat and light. Alternatively, its chemical components can be converted into gasoline.
  • Hot packs involving a chemical reaction to produce thermal energy or cold packs that absorb chemical energy after a reaction.
  • Natural gas and biomass burn to convert chemical energy to heat and light.
  • Photosynthesis changes solar energy into stored chemical energy.

From the above examples, it’s clear that chemical energy can be found in many forms including vehicle airbags.

Electrical Energy

This type of energy is crucial for day-to-day use. Most of our activities in life currently depend on it. Electrical energy results from electric charge flow and it involves electrical repulsion or attraction between the charged particles.

This type of energy can be either kinetic or potential since it’s based on electric charge flow. It’s just like a battery (potential energy) that comes to life when some force is applied to it in order to make its charged particles do work (kinetic energy).

Types of electrical energy

They include:

  • Current electricity: it involves the flow of electric charges on an electric field. Current energy has to flow a conductor and if the charge is constant, then the conductor will end up heating frequently.
  • Hydroelectricity – the electric power is harness from moving water. Hydroelectricity is usually produced on a large scale for commercial use.
  • Static electricity- it involves contact between equal negatively and positively charged subatomic particles. There has to be friction and subatomic particles of opposite type i.e. – and +.
  • Solar electricity – solar power can also be tapped to produce electricity. This usually involves the use of solar panels to tap the solar rays. Solar electricity is mostly used for residential purposes including powering household appliances. In case there are large numbers of solar panels, Solar electricity can also be used for industrial purposes.

Examples of electric energy include:

  • Car headlights
  • A light bulb
  • Lighting during thunderstorms
  • Car battery

Light Energy

It’s a type of electromagnetic radiation that consists of photons. Light energy usually travels in the form of waves. Note that this is the only type of energy that’s visible to the human eye.

But is light energy potential or kinetic type? Well, since it involves electromagnetic radiation and it has no mass, light energy neither fits the description of kinetic nor potential energy. Common types of light energy include:

  • UV light and X-Rays: they are light energies with short electromagnetic waves. X-rays, for instance, are mostly used in the medical sector to photograph the insides of our bodies.
  • Infrared light: it forms part of the electromagnetic spectrum and produces heat.
  • Visible light: this is the only type of energy that’s visible to the human eye. Its main source is usually the sun but it can also be emitted by light bulbs, lanterns, and flashlights.

Light energy consists of photons i.e. tiny energy packets. So, when the atoms in an objected are heated up, it ends up producing photons due to the movements of atoms. More light photons are usually produced when the objects become hotter,

Nuclear Energy

This energy type normally comes from the atoms’ nucleus. Nuclear energy is produced by nuclear fusion i.e. when the nuclei split apart or when they are fused together.

Note that everything in the universe has an atom that consists of electrons, neutrons, and protons. At the center of the atom, there is the nucleus.

So, when the nuclei of the atoms fuse or are combined, it results in nuclear fusion. An example of this process is how the sun usually produces its energy. When the nuclei atoms split, this process is known as nuclear fission and it’s the technique that nuclear plants use to generate electricity.

Nuclear energy is non-renewable. It’s categorized as a potential type of energy since its energy is stored in the nuclei of atoms. Examples of nuclear energy include:

  • Nuclear fission reactions at power plants to produce electricity
  • Nuclear fusion by the sun provides living things with the energy needed for growth and survival
  • Uncontrolled type of nuclear fission reaction with the destructive characteristics of a nuclear bomb.

Motion or Mechanical Energy

It’s a potential and kinetic type of energy that’s possessed by an object due to position or motion. The faster an object moves, the more the energy is stored and vice-versa. Examples of mechanical energy include:

  • A wrecking ball that’s used to demolish buildings
  • An iron hammer with weight (potential energy) and has the ability to do work (kinetic energy)
  • Windmills
  • A fish swimming
  • A person running

Sound Energy

It’s normally produced when an object vibrates causing pressure waves to travel through a medium such as water, air, wood, and metal among others. Sound energy is mechanical in nature and since it involves vibration movements, it’s a type of kinetic energy.

Examples of sound energy include:

  • Air conditioning fan
  • Balloon popping
  • A Doorbell ringing
  • Piano or radio producing sound
  • Stomping your feet or clapping your hands
  • Talking or singing

Other types of energy that you may come across include:

  • Gravitational energy: it’s a type of potential energy that’s associated with the force of gravity. Gravitational energy is usually stored in objects due to their heights above the earth’s surface and this depends on whether it’s too close or far away from the ground.
  • Elastic energy: it’s another type of potential energy that’s found in elastic objects such as a stretched elastic bad or a coiled spring.

Sources of Energy

There are more than 10 main sources of energy that are currently used to generate power. However, there are still more sources being discovered and this number is expected to increase in the future.

Most of these sources of energy are mainly used to generate electric power. Well, this is because the world operates based on a series of several electrical reactions regardless of whether you are simply turning on a light bulb or charging your smartphone.

Solar energy

The sun is the primary source of solar energy. This source of energy is usually harvested by using solar panels. This source of energy can be collected for residential or industrial use. Large solar panels have to place in large open fields or rooftops where the sun’s rays can directly hit the solar panels.

However, there is a restriction that comes with this source of energy. For instance, it’s only ideal in areas where there is enough direct sunlight throughout the way.

Besides that, its effectiveness also depends on different seasons. For instance, the amount of solar energy generated during the winter months is quite low compared to the energy generated during the hot summer months. It’s also worth noting that there is still a need to produce effective solar electricity storage facilities.


Biomass energy comes from plants. It’s normally produced from organic material. Plants have chlorophyll and it normally captures the sun’s energy through photosynthesis by converting CO2 from the air into carbohydrates.

Sources of biomass include:

  • Wood chips
  • Yard clippings
  • Crops and plants
  • Animal wastes

However, this source of energy is toxic to the environment. Biomass energy usually produces large amounts of CO2 into the atmosphere.

It’s worth noting that biomass is also a serious health hazard when used indoors. In case there is poor ventilation when using biomass fuel to cook indoors, then you risk suffering from off-gassing suffocation.

Tidal energy

The rise and fall of the tides can be effective sources of energy. Tidal energy usually uses tides that contain kinetic energy. When the fall and rise of tides are converted into kinetic energy, it ends up producing electrical energy.

However, the generation of tidal energy is mainly restricted to coastal areas where there are frequent tides. The renewable source of energy can be used as a reliable source to produce large amounts of energy for industrial use.

The best thing about this source of energy is that it’s reliable. Tides are still able to generate electrical energy even at low speeds than usual.


This source of energy comes from the earth’s core. This is a renewable type of energy that’s clean and sustainable. As a result, it is environmentally friendly.

The earth is constantly producing high temperatures due to the slow decay of its radioactive particles. As a result, the rocks beneath the earth usually heat the underground water which ends up producing steam. If that steam is effectively captured, then it’s powerful enough to move turbines. These rotating turbines are used to generate energy in the form of hydro-electric power.

Geothermal energy can be produced at selected sites in the world. However, California has the largest collection of geothermal power plants. But utilizing this source of energy comes with several disadvantages including increasing the risk of earthquakes in geological hotspots.

Fossil Fuels

This energy source includes natural gas, oil, and coal. Fossil fuels are non-renewable but they are among the most popular sources of energy. This is because they are versatile and can be easily converted into Manu products.

Even though fossil fuels are common, converting them into different usable forms causes significant destruction as well as pollution to the environment. Besides that, fossil fuel reserves are also not renewable and they are expected to last for 100 years or less.

Wind energy

Just like solar energy, wind energy is also becoming quite popular. That’s why we have more wind farms now than ever before.

Well, this source of energy is tapped with the use of large turbines that turn wind into energy. When the turbines are turned by the wind, they subsequently turn generators that then produce electricity.

But how effective is this source of energy? Well, at the moment, wind energy requires a high amount of investment. Besides that, wind speed isn’t reliable since it can’t be easily tapped from anywhere.


This energy derived from flowing water. Many people are not aware that hydropower is one of the biggest sources of energy that powers most towns and cities.

Hydropower normally comes from dams that are designed to turn turbines that consequentially produce electricity. This is a clean source of energy that doesn’t produce toxic gases.

However, this source of energy is also expensive and requires significant amounts of money to install dams. Besides that, most dams are aged and they need massive restorations in order to be safe and functional. An environmental issue to the people living close to the dams is that they may end up utilizing the same water the hydropower turbines use.

Hydrogen Energy

When we talk about hydrogen power, we are referring to hydrogen that’s found in water (H20), a common element on earth. Note that water contains 2/3 of hydrogen that can still be found in combination with other elements.

But if hydrogen is separated from water, it can be an effective source of energy. Hydrogen is powerful and the energy it produces can help to fuel rockets, ships, industries, and vehicles. It is normally produced in demand even though it’s a renewable source of energy in order to minimize its toxic emissions into the atmosphere.

Nuclear energy

The use of this source of energy is still a great subject of debate. The safety of nuclear energy is one of the factors that limit its use.

Nuclear energy comes from a non-renewable uranium source. It’s created through nuclear reaction before it’s collected and used to generate power.

Most developed countries have built nuclear reactors. The damage that nuclear energy can cause if not effectively manage can have serious devastating effects that can last for hundreds of years.

Uses of Energy

Energy is used in different sectors for various purposes. The industrial revolution changed our need for energy and it has now become an essential part of our lives. It’s impossible to fathom a world that can currently operate without energy. From relaxing at home to cooking, we need energy.

Residential use of energy

  • Cooking: can you imagine a diet that is only composed of raw food? Well, we need the energy to start a fire in order to cook and warm food. This can be in the form of gas power or electrical energy.
  • Heating: energy is crucial for heating purposes especially during the winter season. You no longer need to light firewood to get heat. Because of energy, human beings can now live and thrive in extremely cold environments.
  • Lighting: well, you need the energy to illuminate your home. The light bulbs and lamps need it in the form of electricity or batteries.

Other residential uses of energy include:

  • Powering devices such as computers, TV, laptop, and smart devices.
  • Taking a shower
  • Washing and drying clothes

Industrial use of energy

The use of energy in the industrial sector is mostly for production purposes as well as lighting. It should be noted that manufacturing industries make up almost 50% of energy use globally. Well, industrial production and the use of energy are expected to grow by 1.5% annually until 2035.

Uses of energy in the industrial sector include:

  • Running of industrial machinery and motors
  • Lighting
  • Office equipment
  • Computers and monitoring devices
  • Facility equipment for cooling, heating, and ventilation


If all these forms of energy were not available, then we would be probably still moving around with horse-powered carriages and horses. However, energy has made it possible to conveniently move from one location to another with the use of:

  • Buses and cars
  • Trains
  • Ships
  • Planes

Takeaway of What is Energy in Science

Energy comes from different sources. It could be non-renewable meaning that it gets depleted with every use. On the other hand, it could be renewable meaning that it’s not limited. Generally, energy is versatile in nature and it exists in different types. But regardless of the type, we should always conserve energy to avoid wastage and reduce the chances of environmental pollution.

We should use energy to create a healthy and sustainable planet. We hope that you now have a better understanding of what is energy in science, if so please share this page, thank you.

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