Navigation
An introduction to the concept of energy and how it makes things happen in our world.
Have you ever wondered why a car can zoom down the road, or why your body feels warm after you run a race? It is all because of a 'secret ingredient' called energy!
In science, energy is defined as the ability to do work or cause change. But what does 'work' mean? For a scientist, work happens whenever a force moves something over a distance. Imagine pushing a heavy box across the floor. You are using energy to make that box move! Without energy, nothing in the universe would ever move, grow, or light up. Energy is like the 'fuel' that powers everything from the tiny cells in your body to the giant stars in space. It cannot be seen directly, but we can see what it does.
1. A soccer ball sits still on the grass. It has no movement. 2. You use the energy from your muscles to kick the ball. 3. The ball zooms away! Your energy caused a change in the ball's position.
Quick Check
What is the scientific definition of energy?
Answer
Energy is the ability to do work or cause change.
Energy doesn't just appear out of nowhere; it comes from different sources. The most important source of energy for Earth is the Sun. The Sun provides light and heat that helps plants grow. Humans get their energy from food. When you eat an apple, your body breaks it down to get the stored energy inside so you can think and play. Other things, like toys or flashlights, get their energy from batteries or electricity from a wall outlet.
1. The Sun sends light energy to a corn plant. 2. The corn plant uses that light to grow and store energy. 3. A chicken eats the corn. 4. You eat the chicken and get the energy to run a meter dash!
Quick Check
What is the main source of energy for the entire Earth?
Answer
The Sun.
We use energy for two main things every day: movement and heat. When you see a car driving or a bird flying, you are seeing energy being used for movement. But energy also keeps us warm! When you rub your hands together very fast, they start to feel hot. This is because the energy of your moving hands is being changed into heat energy. Even a toaster uses electrical energy to create heat and turn your bread into crunchy toast.
Think about a toaster. It uses energy in three steps: 1. Electrical energy comes from the wire. 2. The wires inside the toaster turn red and create heat. 3. A spring uses energy to 'pop' the toast up (movement) when it is done!
In science, what is 'work'?
Which of these is a source of energy for a toy car?
Energy can be used to create heat.
Review Tomorrow
Tomorrow morning, try to name three things in your house that are using energy to move or create heat.
Practice Activity
Rub your hands together for 30 seconds. Feel the heat! Then, try to explain to a friend or family member where that heat energy came from.