The world we live in contains not only things we can see, but also many different forms of energy.
Light streaming from the Sun, the atoms and electrons that make up matter, and electromagnetic waves that reach Earth from distant space.
How do these things transmit energy and affect matter?
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1. What Is Energy?
[Types of Energy]
Energy is a physical quantity that describes the ability to move matter or change its state.
There are many different forms of energy all around us.
- Kinetic energy: Energy an object has because it is moving
- Thermal energy: Energy associated with the motion of particles within matter
- Light energy: Energy carried by photons
- Electrical energy: Energy associated with electric charges and electric fields
- Chemical energy: Energy associated with the bonds and arrangements of atoms and molecules
- Energy associated with mass: Energy expressed by Einstein’s “E = mc²”
These forms of energy can be converted from one form to another.
For example, plants absorb sunlight and convert it into chemical energy, while solar cells convert light into electrical energy.
In other words, energy is a fundamental part of nature that underlies every change that takes place.
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2. How Does Matter Receive Energy?
[How Electrons Receive Energy]
Our bodies and the materials around us are made up of atoms and molecules.
Typically, an atom has a nucleus at its center, with electrons around it.
Electrons can move to a higher energy state by receiving energy from outside the atom.
① Receiving Energy from Photons
Light has particle-like properties and is made up of particles called “photons.”
When an atom absorbs a photon, the energy can cause an electron to move to a higher energy state.
② Receiving Energy from an Electric Field
Particles with electric charge create electric fields around them.
An electrically charged object is an object that has electrical properties.
There are two types of electric charge:
Positive (+) charge: The charge carried by protons
Negative (−) charge: The charge carried by electrons
Objects normally contain both protons and electrons. Since their charges cancel each other out, the object as a whole is electrically neutral.
However, this balance can be disrupted when electrons move.
The uneven distribution of electrons determines whether an object has a positive or negative charge.
For example, rubbing a plastic ruler against your hair causes electrons to move from one to the other, producing static electricity.
In this way, an object whose balance of positive and negative charges has been disrupted is called a “charged object.”
Electric fields created by electric charges exist over a vast range, from the world around us to outer space.
An electric field exerts a force on electrons, and when electrons move under that force, their kinetic energy may increase.
How Lightning Forms ⚡️
Lightning is an electrical discharge that occurs when positive (+) and negative (−) charges separate within a cloud, creating a strong electric field.
Charged particles, such as electrons, move and collide with atoms and molecules in the air.
As a result, the atoms and molecules enter higher energy states and emit photons.
This is what produces the light of lightning.
③ Receiving Energy from Heat or Particle Collisions
When matter is heated, the atoms and molecules within it move more vigorously.
Energy can also be transferred through collisions between particles, changing the state of electrons.
In these ways, matter receives energy through various means and undergoes change.
How a Microwave Oven Heats Food 🔋
A microwave oven heats food by using electromagnetic waves to move water molecules and other particles in the food, converting that energy into heat.
A microwave oven generates electromagnetic waves at approximately 2.45 billion Hz.
Because water molecules have an uneven electrical charge, they try to reorient themselves in response to changes in the electric field.
When the electric field changes, water molecules try to reorient themselves.
However, because water molecules interact with one another inside food, they cannot fully keep up with changes in the electric field.
This lag transfers the electromagnetic wave’s energy into the molecules’ irregular motion inside the food, raising its temperature.
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Energy is what makes up the world around us and the human body, and understanding how it works can help us shift from using energy unconsciously to using it consciously and recognize the many diverse possibilities already within us.