15 Energy!

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Energy by Liane B. Onish Table of Contents Introduction page 2 Chapter 1 Light Energy page 4 Chapter 2 Heat Energy page 8 Chapter 3 Sound Energy page 12 Conclusion page 14 Glossary/ Index page 15 Comprehension Check page 16

Introduction Do you need energy to run like the wind? Of course you do. But do you need energy to sing a song or smile? Yes, singing and even smiling take energy. You use energy all the time. Energy is the ability to do work. It is what makes things happen, move, and change. You use energy when you read a newspaper or when you shudder in fear at a scary movie. Energy helps your numb fingers form a snowball. Where does the energy you need to run a race, read, or sing come from? Your get-up-and-go, your energy, comes from the food you eat. The energy in the food you eat comes from the sun. There are many different kinds of energy. This book will explore three kinds of energy you use every day: light, heat, and sound. When you read outdoors, you use light energy from the sun. Burning charcoal gives off heat energy for cooking. Singing and playing musical instruments creates sound energy.

Chapter 1 Light Energy On a sunny day, you can see because of light energy from the sun. The sun does more than just light up the sky. The sun makes life possible. Almost everything that grows needs light energy. Plants absorb light from the sun. Then plants change the sun's energy into energy they can use to grow. Some of that energy is also stored in the plants. When people and animals eat plants, they get the stored energy from the sun. The same energy that helps plants grow also provides food for animals and people. The grass absorbs energy from the sun as it grows. The cow absorbs energy from the sun by eating grass in a field. People get some of the sun's energy that is stored in the cow's milk. See What Happens Plants use light energy from the sun to make food. A green substance in plants, called chlorophyll, absorbs sunlight to help the plant make the food it needs to grow. What happens when plants do not get the light they need? Cover one leaf of a plant with foil. The foil will block out the sunlight. In about five days, the covered leaf will turn yellow, because it was not getting the light it needed to grow. These plants are getting the light they need to grow. The energy we need to grow and stay alive comes from food. When you eat, the energy in the foods changes into a form of energy your body can use. Your body uses the energy to grow and help you stay alive. You use the energy to work and play.

Wear White At Night If you are outside at night, wearing white and shiny fabrics can help you to stay safe. People in cars can see you better when the cars' headlights reflect off your white or light- colored clothing. Shiny silver strips on bikes, helmets, and sneakers also help reflect light. What is light? Light is a wave that travels in a straight line. Light can travel through space, air, water, and some objects. Nothing travels faster than light. That's a good thing, because the light that makes life possible comes from the sun. The sun is 93 million miles from Earth. The sunlight you see and feel right now actually left the sun about eight minutes ago. Sunlight travels in a straight line. Light from a lamp, candle, or other source also travels in a straight line. When light hits an object, some light bounces, or reflects, off the object. The reflected light enters your eyes, letting you see the object. Certain surfaces reflect light. A shiny smooth surface reflects light well. A mirror is a good light reflector. Light can be blocked. A solid object in the path of light blocks it. Blocked light forms a shadow. Light can also be bent. When light passes from air into water, it bends, or refracts. The image of a flower stem in a vase is not broken. It looks broken because light passing through the water refracts. Light appears white, but it is really a rainbow of colors. You see a rainbow when light passes through raindrops in the air. The raindrops bend the light so much that people can see its true colors. You can make a hand shadow like this one by blocking the light rays from a lamp, flashlight, or other source. Water refracts rays of light, making the object in the water appear broken.

Chapter 2 Heat Energy Heat energy also comes from the sun. It warms the air and melts snow. Heat energy can make matter change. When you add heat to water, it boils. Heat changes water into a gas, called steam. When you take heat away, water freezes. Taking heat away changes water into ice. Heat energy begins with the sun. But heat energy comes from other sources, too. snow water Heat energy from the sun melts snow, a solid, turning it into a liquid, water. Heat energy from electricity boils water, a liquid which escapes as steam, a gas. steam water Taking heat energy away freezes water, a liquid, turning it into a solid, ice. ice water coal oil It takes millions of years for dead plants and animals to turn into fossil fuels. Much of the heat energy we use today comes from burning fossil fuels. Fossil fuels are coal, oil, and natural gas. All fossil fuels were once living plants and animals. These plants and animals died a very long time ago. They became covered with layers of dirt, rocks, clay, and mud. Over millions of years, the remains slowly changed. Some turned into natural gas. Some became a kind of rock called coal. Some remains turned into oil. When we use fossil fuels, we are using energy stored in plants and animals that are millions of years old. However, the supply of fossil fuels is running out.