All About Energy

Science, Grade 3


Table Of Contents: All About Energy

1. What is Energy?
Energy is the ability to make an object move or cause a change in matter. You can't always see or touch energy, but it is everywhere. To find energy, look for motion, heat, light, sound, or electricity.
2. Energy for Life
We use many forms of energy every day. We use energy to heat, cool, run appliances, light our homes, and run our cars. We use the stored energy in food to keep us warm, maintain our bodies, and move about. Other living organisms need energy too. Plants use light, energy to grow and make food.
3. Energy from the Sun
The Sun provides most of the energy on Earth. Plants absorb light energy from the Sun and use it to make food stored as chemical energy. The energy stored in plants in turn provides the energy for other living things on Earth. The Sun's energy also provides warmth, powers the water cycle, and makes wind power.
4. Energy in Motion - Kinetic Energy
There are two main types of energy- potential energy and kinetic energy. Kinetic energy is energy that is in motion. A moving car, a bouncing ball, and a spinning top have kinetic energy. In contrast, potential energy is stored energy.
5. Stored Energy - Potential Energy
Energy that is stored and ready to go is potential energy. For example, a skier at the top of the hill who is not moving has potential energy, due to gravity. When the skier starts moving downhill, the potential energy changes into kinetic energy. Other examples include the energy stored in a stretched rubber band, food, and wood.
6. Chemical Energy
Chemical energy is potential energy stored in the bonds that hold matter together. It is released during a chemical reaction. Food has potential energy. When we digest food, the stored energy from the food is released in the form of kinetic energy and heat. Other sources of chemical energy include wood, batteries, and gasoline.
7. Sound Energy
Sound is kinetic energy that is caused by vibrations passing through matter. These vibrations can be carried by air, water, or solid objects. When you pluck a guitar string, the vibration of the string makes air move in waves. This causes movement of our eardrums and we can hear it as sound.
8. Light Energy
Light is a type of kinetic energy that we can see. Light is all around us and comes from the Sun, lamps, and many other sources. Light travels as waves in straight lines, except when it strikes an object. Then, it may pass through the object, reflect off of the object, or be absorbed by the object.
9. Electrical Energy
Electrical energy is kinetic energy that comes from electric current. Any appliance or device that is plugged into an electrical outlet uses electricity. Electrical energy changes to other forms of energy, like light, when the switch is turned on.
10. Thermal Energy
Have you ever wondered what makes something hot? All matter is made up of tiny particles called atoms. These particles within an object start to move as the temperature rises. The movement of these particles in matter produces thermal energy. We feel the flow of thermal energy as heat. Heat naturally flows from a warmer object to a colder object.
11. Transfer of Energy
All energy is connected and moves from one form to another. For example, chemical energy in gasoline turns into heat, sound, and motion as it burns. Energy from a soccer player's foot is transferred to the soccer ball as he kicks it, making it move. Energy cannot be made nor destroyed, but it can change form or transfer from one object to another.
12. Energy Flow in an Ecosystem
In an ecosystem, which consists of a group of living things and the environment in which they live, plants capture energy from the Sun. When an organism eats the plant the energy is then transferred to that organism. This process is referred to as energy flow. In this food chain example, energy flows from the grass, to the grasshopper, to the frog.
13. Energy Sources
The energy we use every day comes from a variety of sources. Fossil fuels, such as oil and coal, are nonrenewable. These energy sources can only be used once and cannot be replaced. Other energy sources, such as solar and wind power energy, are powered by sources that are naturally replaced and are considered limitless. These are called renewable energy sources.