Energy Types and Conservation
Grade 7 · Science · Study Guide
Explore the different forms of energy and how energy is never destroyed — only transformed.
Energy is the ability to do work — to cause a change. It comes in many forms, but it never disappears. The Law of Conservation of Energy is one of the most fundamental laws in all of science: energy cannot be created or destroyed, only converted from one form to another.
The two broadest categories are kinetic energy (the energy of motion) and potential energy (stored energy). A moving baseball has kinetic energy. A baseball held up high has gravitational potential energy because gravity could accelerate it downward. The moment you release it, that potential energy converts to kinetic energy as it falls. When it hits the ground, that kinetic energy converts to sound energy, heat, and briefly, the deformation of the ball. The total energy in the system is always conserved.
Other important forms of energy include: thermal energy (the total kinetic energy of all particles in a substance — related to temperature), chemical energy (stored in the bonds of molecules — like food, fuel, and batteries), electrical energy (the movement of charged particles through a conductor), radiant energy (electromagnetic waves like light, radio waves, and X-rays), nuclear energy (stored in the nucleus of atoms — released by fission or fusion), and sound energy (mechanical waves traveling through matter).
Energy conversions are happening constantly around you. A toaster converts electrical energy to thermal energy (and some light). A plant converts radiant (light) energy to chemical energy through photosynthesis. Your body converts chemical energy (food) to mechanical energy (movement) and thermal energy (body heat). Understanding energy transformations is central to engineering, environmental science, and everyday life — from solar panels to electric cars.
Key terms
- Kinetic energy
- The energy an object has due to its motion; KE = ½mv².
- Potential energy
- Stored energy that has the potential to do work; includes gravitational and chemical forms.
- Law of Conservation of Energy
- Energy cannot be created or destroyed — only converted from one form to another.
- Thermal energy
- The total kinetic energy of all the particles in a substance, related to temperature.
- Chemical energy
- Energy stored in chemical bonds between atoms and molecules.
- Mechanical energy
- The sum of an object's kinetic and potential energy.
Flashcards
- Law of Conservation of Energy
- Energy is never created or destroyed — it only changes form.
- Kinetic energy
- Energy of motion; KE = ½mv². Depends on both mass and velocity.
- Potential energy
- Stored energy waiting to be released; includes gravitational, elastic, and chemical forms.
- Thermal energy
- The total kinetic energy of all particles in a substance; increases with temperature.
- Radiant energy
- Energy carried by electromagnetic waves (light, UV, infrared, X-rays, radio waves).
- Chemical energy
- Energy stored in chemical bonds; released during chemical reactions (burning, digestion).
Practice questions
What type of energy does a stretched rubber band have?
- Kinetic energy
- Thermal energy
- Potential energy
- Nuclear energy
Show answer
Answer: Potential energy
A stretched rubber band has elastic potential energy — stored energy from its deformed position. When released, that potential energy converts to kinetic energy.
According to the Law of Conservation of Energy, energy can be destroyed when used.
Show answer
Answer: False
The Law of Conservation of Energy states energy is NEVER destroyed. When it seems to 'disappear' (like a bouncing ball that slows down), it has converted to thermal energy (heat) and sound.
The energy of motion is called ___ energy.
Show answer
Answer: kinetic
Kinetic comes from the Greek word 'kinesis' meaning movement. Any moving object — from electrons to planets — has kinetic energy.
When a roller coaster reaches the bottom of a hill, most of its potential energy has been converted to what?
- Nuclear energy
- Chemical energy
- Kinetic energy
- Radiant energy
Show answer
Answer: Kinetic energy
As a roller coaster descends, gravitational potential energy converts to kinetic energy (speed). At the very bottom, kinetic energy is at maximum and potential energy is at minimum.
Chemical energy is stored in the bonds between atoms and molecules.
Show answer
Answer: True
Chemical energy is the energy stored in the arrangement of electrons and atoms in chemical bonds. Breaking these bonds (in combustion, digestion, etc.) releases that energy.
Fun facts
- The energy in a single bolt of lightning could power a 100-watt light bulb for about 3 months — but harnessing it is nearly impossible.
- Nuclear energy from splitting one kilogram of uranium releases as much energy as burning about 3 million kilograms of coal.
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