Heat Energy a Science A–Z Physical Series Word Count: 947 Heat Energy

Heat Energy A Science A–Z Physical Series Word Count: 947 Heat Energy

Written by Felicia Brown

www.sciencea-z.com Visit www.sciencea-z.com Key elements Used in This Book The Big Idea: One of the most important types of energy on Earth is heat energy. A great deal of heat energy comes from the Sun’s light Heat Energy hitting Earth. Other sources include geothermal energy, friction, and even living things. Heat energy is the driving force behind everything we do. This energy gives us the ability to run, dance, sing, and play. We also use heat energy to warm our homes, cook our food, power our vehicles, and create electricity. Key words: cold, conduction, conductor, convection, energy, evaporate, fire, friction, fuel, gas, geyser, heat energy, hot, insulation, insulator, lightning, liquid, matter, particles, radiant energy, solid, Sun, temperature, thermometer, transfer, volcano Key comprehension skills: Cause and effect Other suitable comprehension skills: Compare and contrast; classify information; main idea and details; identify facts; elements of a genre; interpret graphs, charts, and diagrams Key reading strategy: Connect to prior knowledge Other suitable reading strategies: Ask and answer questions; summarize; visualize; using a table of contents and headings; using a glossary and bold terms

Photo Credits: Front cover: © iStockphoto.com/Julien Grondin; back cover, page 5: © iStockphoto.com/ Arpad Benedek; title page, page 20 (left): © iStockphoto.com/Anna Ziska; pages 3, 9, 20 (right): © Jupiterimages Corporation; page 4: © iStockphoto.com/Nancy Louie; page 6 (left): © iStockphoto.com/Sreedhar Yedlapati; page 6 (right): © iStockphoto.com/Diane Diederich; page 7 (left): © iStockphoto.com/Yuri Hnilazub; page 7 (right): © iStockphoto.com/Alexander Hafemann; pages 10, 11: © iStockphoto.com/bubaone; page 13: © iStockphoto.com/Milorad Zaric; page 16 (top): © iStockphoto.com/Mik111; page 16 (bottom right): © iStockphoto.com/Craig Veltri; page 16 (bottom left): © iStockphoto.com/Amanda Rohde; page 21 (top): Sheryl Shetler/© Learning A–Z; page 21 (bottom): © iClipart.com; page 22: courtesy of NASA/JPL-Caltech

Illustration Credits: Pages 8, 12, 14, 15, 17, 18, 19: Cende Hill/© Learning A–Z

Written by Felicia Brown

www.sciencea-z.com Table of Contents Heat energy cooks these marshmallows. Introduction...... 4 Introduction Sources of Heat Energy...... 5 Have you ever stood next to a campfire? Have you ever watched Temperature...... 10 soup boil? Then you have seen Heat Moves Through Things...... 13 and felt heat energy at work! Conduction...... 14 There are many kinds of energy. But Convection...... 17 you use heat energy all the time. Heat Energy and You...... 20 In this book, you will learn where Glossary...... 23 heat energy comes from, how it Index...... 24 moves, and much more. 3 4 Sources of Heat Energy

Rub your hands together very fast. Do they feel hot? The heat is caused by friction. Friction happens when two objects rub together. Friction is one way to make heat! Fuel makes cars run. It also makes the electricity we use every day.

Burning fuel is another way we get heat. Gasoline is a kind of fuel. When gasoline burns, it makes heat energy. The heat energy is used to make cars and trucks run.

Electricity also makes heat energy. Toasters, irons, and hair dryers use electricity to make heat. Electric Rubbing your hands and wearing warm clothing help keep you warm. furnaces heat homes and schools. 5 6 Heat comes from nature, too. Lightning is a natural source of heat. And did you know that Some of the heat energy radiates away Earth has its own heat deep and is absorbed by Earth receives the atmosphere. underground? It is so hot in the light energy middle of Earth that rocks melt. from the Sun. Sometimes the melted rocks come close to the surface and heat water Land, air, and water absorb light energy that shoots out of the ground. This and warm up. shooting water is called a geyser. A lot of our energy comes from the Sun. Have you ever stepped from the shade into sunlight and felt warm? Sunlight is radiant energy. Radiant energy comes in many different forms. When sunlight hits your skin, it changes to heat. Another form of radiant energy Nature can melt rocks, heat water underground, and make gorgeous displays of heat energy. cooks the food in your microwave. 7 8 Heat energy always moves from Temperature warm places to cool places. When Everything you can touch—all sunlight hits the ground, it turns matter—is made up of particles, to heat. Then the heat moves to too small to see. These particles are the cool air. Heated air keeps always moving a tiny bit. Every Earth warm. object also has heat energy. How much heat energy an object

Dark things take in more of the Sun’s has affects how quickly energy than light-colored things. its particles move. That’s why light-colored clothes keep you cooler on a hot summer day. So which would feel warmer: a white rock or a black rock?

The heat energy of each particle affects how fast it moves. 9 10 We use temperature to know how much Temperature is measured in degrees heat energy things have. The hotter (°) using either the Celsius (C) or something is, the more heat energy it Fahrenheit (F) scale. has. The more heat energy it has, the higher its temperature. The higher its temperature, the faster its particles move. The less heat energy something has, the colder its temperature. The colder its temperature, the more slowly its particles move. We use a thermometer to measure temperature.

Water freezes at 0°C (32°F), and it boils at 100°C (212°F). A thermometer can tell you how hot or cold the water is.

Thermometer comes from two words. Thermo means “heat.” Meter means “an object used to measure.” So a thermometer is an object When particles have more heat, they used to measure how hot something is. move faster. 11 12 Heat Moves Through Things Conduction

You know that the temperature of Heat moves easiest through solids. an object can change. Pizza can This is because the particles in solids be hot from the oven. Later, the are closer together than the particles pizza gets cold. The pizza changes in air or liquids. Heat moves through temperature because heat energy solids by conduction. moves through it. Heat energy Gas: Particles are farthest apart. Heat moves through solids (such as pizza) moves slowest through a gas. and liquids and gases (such as water and air). Heat energy always moves from a warmer object to a cooler Liquid: Particles are closer together. object. But it moves differently Heat moves more quickly through a through solids than it moves liquid than a gas. through liquids and gases.

Solid: Particles are closest together, and in a pattern. Heat moves Heat moves through particles in pizza. through easily. 13 14 Particles higher up A good conductor are still cool and slow. is something that Particles in the heat can move fire get hot and move fast. through easily. Metal is a good conductor. Pots and pans are A metal pot is a good conductor. made of metal because it helps food cook fast. What happens to the particles in this metal rod when they touch fire? A good insulator is something that heat cannot move through easily. First, they get heat energy from the Wood and plastic are good fire. The heat energy makes them insulators. Heat energy moves move fast. The hotter particles bump slowly in these into other, cooler particles in the rod. solids. Pan This makes the cooler particles heat handles are up and move faster. The heat energy made of wood transfers up the rod until all its and plastic particles are hot. In time, the rod will because they Travel mugs keep heat in, be too hot to hold! stay cool. but oven mitts keep heat out. 15 16 Now the soup at the top of the pot is cooler. It is also heavier, so it sinks! The heavier, cooler soup pushes the lighter, hotter soup up to the top. This is why soup churns cool soup and boils as it gets hot! soup heats up burner heats the pan

Convection

Let’s look at how heat moves through a liquid, such as soup. A hot pot heats the soup at the bottom particles close first. The heat makes these soup together and moving slowly particles move fast. They spread out. When the particles spread out, particles far apart and the soup gets lighter! The soup at moving fast the bottom of the pot becomes lighter than the soup at the top. 17 18 Heat Energy and You

Your body has ways to keep cool and stay warm. When you get too hot, you sweat. As sweat evaporates from your skin, it takes heat away from your body. Now your skin has a lower temperature, Energy from the Sun turns to heat when it is absorbed by the ground. Then heat from the ground warms the air above it. and your body feels cooler. To stay Cooler air from above pushes the warm air up. warm, you wear thick clothes. Now let’s learn how heat warms gas, They help keep in the heat. such as air. When the ground warms the air above it, the air rises. The heavier, cooler air from above sinks and pushes the warmer air up. Cooler air is always sinking and pushing up warmer air. The moving air is called wind! Heat energy moving through liquid or gas is Your body needs to stay at about the same temperature, called convection. whether it’s hot or cold outside. 19 20 Most of our energy comes from the Sun.

Insulation has many tiny air pockets. Air is a good insulator. You have learned many things about heat. Heat is one kind of We put insulation in our homes to energy. Heat is an energy that we help keep out hot air during the use every day. Heat moves through summer. Insulation also helps keep solids, liquids, and gases. Heat in warm air during the winter. moves from hot things to cool things. We use temperature to Imagine being lost outside in the woods. tell how hot or cold something is. You have no matches to start a fire,

and it is cold. How would you stay warm?

grass on yourself to stay warm. stay to yourself on grass Heat energy comes from many

friction makes them burn, or pile leaves and and leaves pile or burn, them makes friction branches and brush, rub sticks together so so together sticks rub brush, and branches places, such as fuels, the Sun,

Possible answers: Build a shelter from from shelter a Build answers: Possible and volcanoes. 21 22 Glossary heat energy a form of energy that conduction the transfer of heat from transfers from an object one object to another with a higher temperature (p. 14) to an object with a lower temperature (p. 4) conductor a material, usually a metal, that transfers heat, insulator a material that reduces or electricity, or sound from prevents the transfer of one object to another (p. 16) heat (p. 16) convection the transfer of heat by matter anything that takes up movement in a liquid space and has weight or gas (p. 19) (p. 10) evaporate to change from a liquid radiant energy energy that travels state to a gas state (p. 20) in waves (p. 8) friction a force that builds up and temperature the measure of hot and creates heat when two cold, usually measured objects rub against each on a thermometer (p. 11) other (p. 5) thermometer a tool used for measuring fuel any material used to temperature (p. 11) produce heat or power transfer to move from one place (p. 6) to another (p. 15) geyser a hot spring that boils from Index time to time, sending a cooking, 4, 8, 16–18 sunlight, 8, 9, 19 column of water and steam into the air (p. 7) particles, 10–11, 13–15, 17, 18 23 24