Sources of Energy

First things first, the Sun is the most important energy source for all life on earth. The Sun is a key ingredient when plants make energy through photosynthesis. Photosynthesis allows plants to make their own food, and we will discuss it more in another chapter. The sun can also create electricity through solar panels. The sun provides energy in the forms of heat and light. Without the sun, life on earth would not exist! That is why the sun is the most important energy source.

There are different types of energy across the Earth. Plant energy is easy to eat, but hard to use in power plants. We use different types of energy for different purposes! For example, there are many types of energies that power cars and electrical plants. Energy can be created from coal, oil, water, natural gas, and wind. Now, I bet you are thinking, how does oil create energy? Or even wind? Well, we use oil to make gasoline that makes cars go! And perhaps, you’ve driven by a farm or a hilly area on a road trip, and came across these gigantic, white-colored windmills! Well these gigantic windmills are actually called wind turbines. Wind turns a wind turbine and this rotation is used to generate electricity. Coal and natural gas are also used to produce electricity.

Sources of energy are put into two groups: nonrenewable and renewable. 

Nonrenewable means cannot be renewed quickly. Nonrenewable sources are used faster than they can be replaced. This means that their supply is limited. Coal, natural gas, and oil are some examples of nonrenewable energies. These three sources of energy are also known as fossil fuels. Fossil fuels are made from fossils of plants and animals that died millions of years ago. They were alive millions and millions of years ago. Back then, they gained energy and now that energy is stored as coal, gas and oil. It takes millions of years to make this type of energy, so we cannot replace the coal, gas and oil that we use.

Renewable means can be renewed quickly. Renewable sources are unlimited or very common on our planet. For example, the sun creates a tremendous amount of energy every moment and will burn for billions of years. We call this solar energy. Read on to the text box to learn how the sun and water come together to make electricity. 

Scientists Take Notes! Often you will learn about two terms at the same time because they are related but opposite. Here is one way to take notes when you have this situation.

Scientists Write! Grab a piece of paper and write three things that will be in this book:

Writing paragraphs advice: This last sentence is your topic sentence. The other three details will form your paragraph’s body. Then, write a final sentence that ties all your ideas together. The paragraph introduces an idea, explains it and summarizes it.

Energy is not Created or Destroyed

It’s crazy when you first hear it! Energy is not created when we turn on a light or start a fire. This energy was already stored in a power plant or inside a piece of wood. Then, we did something that changed the stored energy into energy we use. This big idea is called the Law of Conservation of Energy. The Law of Conservation of Energy states that energy cannot be created or destroyed. It can only change between different forms. This law means that energy can change forms many times but it is never truly created or lost. That’s a big idea!

Here are some examples that show what the Law of Conservation of Energy means:

• We do not create energy when we burn gasoline in cars. We are actually turning the energy stored in gasoline into heat and energy that moves the car. (And, you remember that gasoline got this energy from plants that stored the solar energy millions of years ago).
• A water wheel does not create energy. It takes energy from moving water and changes it to energy that rotates an axle.
• A spark starts a fire that releases chemical energy stored in a log. Even though the fireplace “creates” heat, it is simply releasing stored energy in the burning material. The heat and the light are the new forms of energy created by fire.
• You get energy from food. This energy is then stored all over your body. Your muscles use this energy to turn pages in your favorite book and your brain uses this energy to help you think about what you just read.

Energy Changes Forms

You will need to explain how energy changes to do work. For example, energy from the sun powers a toy car with a solar panel. Energy from fossil fuels can power an airplane’s motor. Energy from a waterfall can turn a wheel in Hoover Dam that makes electricity. The big idea in each example is converting energy into work that is useful for us.

Energy is not only converted by machines, you now know that you do it every second of every day! Our bodies convert energy often. Our bodies store chemical energy from the food we eat.  Our brains use electrical energy to signal our hands to hold a book. Our brains even use electrical energy to tell our eyes to blink even though we do not think about it! Because our bodies are always using energy, we need to constantly add energy to our bodies. That’s why we eat!

Solar Energy Powers the Water Cycle

Solar energy is an important part of the water cycle. The water cycle describes how water moves from the Earth, into the air, and back to the Earth’s surface. It is powered by heat from the sun. Without the sun, there would be no water cycle. The sun heats the water up and makes some of the water evaporate. When water evaporates it turns into a gas that goes up in the air. Eventually it gets so high that it can form clouds. When water is a gas it is called steam or water vapor. This water can condense back into water or even freeze into ice when it is high in the sky. It weighs so little that is able to float (for a while) because the sun is heating the Earth which continues to push air upward.

Water in clouds can eventually fall back to Earth as rain or snow. Water sticks to other water very easily. In clouds, tiny drops of water connect with other drops of water and get bigger and bigger. When they get too big, they will start to fall back to earth. If this water immediately runs into a river, lake or ocean, it is still in the water cycle. If this water is immediately absorbed by a plant’s roots, then it helps the plant make energy (more on that next chapter!). If that water falls in your mouth, it is delicious!

Think about the energy that this process takes! The sun is warming water on earth, which makes it move. As water drops get higher, they gain the potential energy to fall back to earth. When the drops get big enough, they fall back to earth. The energy from falling rain can move pebbles and dirt as water runs into streams. And, the energy stored in water can be used by plants to grow tall, make seeds, and sink roots deep into the earth. All this energy starts with the sun and is transformed over and over again. It’s a great example of how energy changes forms but never is destroyed!

Humans use water’s energy. Smart!

Humans have figured out that energy from the water cycle can be used to produce electricity. Hydropower is creating energy (such as electricity) from moving water. When water is released from a reservoir, which is a large lake that stores water, it enters a turbine. The turbine spins the water. The turbine is connected to a generator, so when the turbine spins the generator produces electricity. Hydropower uses energy to create work. That work is making electricity. Hydropower uses moving water, which we consider to be renewable (remember “renewable” from chapter 1?). Why is moving water renewed? Because the water cycle allows water to circulate across the earth all the time. The water cycle is an endless, recharging cycle, which makes hydropower a renewable energy source. 

Scientists Write! This time you will create an argument. First, choose your argument by circling your point of view:

Solar energy powers the water cycle.          Solar energy does not power the water cycle.

Write your paragraph defending your argument and upload it here.