Energy and Energy Resources

Size: px

Start display at page:

Download "Energy and Energy Resources"

Dortha Phelps
7 years ago
Views:

1 CHAPTER 5 LESSON 2 and Resources Transformations Key Concepts What is the law of conservation of? How does friction affect transformations? How are different types of used? What do you think? Read the two statements below and decide whether you agree or disagree with them. Place an A in the Before column if you agree with the statement or a D if you disagree. After you ve read this lesson, reread the statements to see if you have changed your mind. Before Statement After 3. can change from one form to another. 4. If you toss a baton straight up, total decreases as the baton rises. Identify Main Ideas Highlight the sentences in this lesson that talk about how changes form. Use the highlighted sentences to review. 1. Identify Which transformation pops the corn kernels? 3 1 Electrical transfers from the electric outlet to the microwave oven. Radiant changes into thermal as the popcorn kernels absorb the microwaves. This causes the kernels to become hot and pop. Changes Between Forms of Have you ever made popcorn in a microwave oven? changes form when you make popcorn, as shown below. A microwave oven changes electric into radiant. Radiant changes into thermal in the popcorn kernels. Thermal causes water in the popcorn kernels to turn to steam. Pressure builds and they explode. These changes from one form of to another are called transformations. As you watch TV, transformations occur in the television. A television transforms electric into sound and radiant. 2 The microwave oven transforms electrical into radiant. 82 and Resources Reading Essentials

2 Changes Between and Potential transformations also occur when you toss a ball upward, as shown in the figure. The ball slows down as it rises and speeds up as it falls. The ball s speed and height change as the changes from one form to another. to Potential In the figure, notice that the ball is moving fastest and has the most kinetic (KE) as it leaves the girl s hands. As the ball moves upward, its speed and kinetic decrease. At the same time, the ball s potential (PE) increases because the ball s height increases. The ball s kinetic is changing to potential as the ball moves upward. At the ball s highest point, its gravitational potential is greatest and its kinetic is the least. B KE PE Potential to At the ball s highest point, it has the most potential because it is farthest from the ground. As the ball moves downward, its potential decreases because its height decreases. At the same time, the ball s kinetic increases because its speed increases. As the ball drops, potential changes to kinetic. When the ball reaches the boy s hands, the ball s kinetic is at the highest value again. changes between kinetic and potential as the ball moves. However, look at the bars in the figure. The ball s total does not change. A C D E 2. Compare When is the gravitational potential the greatest? Reading Check 3. Explain Why does the potential decrease as the ball falls? Reading Essentials and Resources 83

3 Key Concept Check 4. Define What is the law of conservation of? 5. Explain Which type of is constant in the figure? Why? The Law of Conservation of The total in the universe is the sum of all the different forms of everywhere. According to the law of conservation of, can be transformed from one form into another or transferred from one region to another, but cannot be created or destroyed. The total amount of in the universe does not change. Friction and the Law of Conservation of Sometimes it seems as if the law of conservation of is not accurate. Imagine riding a bicycle, as shown below. The moving bicycle has mechanical. What happens to this mechanical when you apply the brakes? According to the law of conservation of, the bicycle s mechanical is not destroyed, but it is transformed. When you apply the brakes, the bicycle s mechanical is transformed into thermal, as shown below. The brake pads rub against the bicycle s wheels. The additional thermal warms the brakes, wheels, and air around the bicycle. Coasting Applying brakes Stopped + Thermal = Key Concept Check 6. Specify Friction causes what transformation? + Thermal = Thermal Friction When the bicycle s brake pads rub against the moving wheels, friction occurs. Friction is a force that resists the motion of two surfaces that are touching. Friction between the brake pads and the moving wheels changes the bicycle s mechanical into thermal. The total amount of never changes. There is always some friction between any two surfaces that are rubbing against each other. As a result, some mechanical is always transformed into thermal when two surfaces rub against each other. + = 84 and Resources Reading Essentials

4 Reducing Friction It is easier to pedal a bicycle if there is less friction between the bicycle s parts. With less friction, less of the bicycle s mechanical gets transformed into thermal. One way to reduce friction is to apply a lubricant such as oil to surfaces that rub together. Using You use different forms of to do different things. You use radiant from a lamp to light a room. You use chemical stored in your body to run a race. usually changes from one form to another when you use it. For example, a lamp changes electric to radiant that lights a room. Some of the electric also changes to thermal. Thermal causes the lamp s bulb to become warm to the touch. Using Thermal All forms of can be changed into thermal. Recall that thermal is the due to the motion of particles that make up an object. People often use thermal to provide warmth or cook food. An electric space heater changes electric to thermal that warms a room. In a jet engine, burning fuel releases thermal that the engine changes into mechanical. Using Recall that chemical is that is stored in foods and fuels. During photosynthesis, plants change the Sun s radiant into chemical that they store in chemical compounds. Some of these compounds become food for other organisms. Your body transforms chemical from food into kinetic that you use for movement. Your body also transforms some of the chemical into thermal that keeps you warm. Using Radiant A cell phone sends and receives radiant using microwaves. When you speak into a cell phone, the phone transforms sound into electric and then into radiant. Sound waves from your voice carry into the phone. The phone converts the sound into electric and then into radiant. Microwaves carry the radiant away. When you listen to someone on a cell phone, the phone is transforming radiant into electric and then into sound. Make a side-tab book to organize your notes on transformations. Transformations Potential Radiant Electrical Reading Check 7. Name What are two uses of thermal? 8. Sequence What changes take place when you speak into a cell phone? Reading Essentials and Resources 85

5 Key Concept Check 9. Restate What happens to when it is used? 10. Interpret Circle three areas on the cars where one form of is being transformed into waste. Using Electric Remember that electric is the carried by an electric current. Many of the devices you use every day, such as a handheld video game, an mp3 player, and a hair dryer, use electric. Some devices, such as hair dryers, use electric from an electrical power plant. Other devices, such as handheld video games, transform chemical stored in batteries into electric. Waste When changes form, some thermal is always released. For example, a lightbulb converts some electric into radiant. However, the lightbulb also transforms some electric into thermal. This is what makes the lightbulb hot. Some of this thermal moves into the air and cannot be used. Scientists often refer to thermal that cannot be used as waste. Whenever is used, some is transformed into useful and some is transformed into waste. in gasoline makes cars move. However, a car transforms most of the chemical in gasoline into waste. The waste is thermal that moves into the air. As shown below, some of this thermal makes the car s engine hot. Hot gases in the car s exhaust contain thermal produced by burning fuel. Friction between a car s tires and the road changes mechanical to thermal. 86 and Resources Reading Essentials

6 Mini Glossary friction: a force that resists the motion of two surfaces that are touching law of conservation of : can be transformed from one form into another or transferred from one region to another, but cannot be created or destroyed 1. Review the terms and their definitions in the Mini Glossary. Write a sentence that provides an example of friction. 2. Use what you have learned about to complete the table. Change Example Change Example to potential Throw a ball into the air. to thermal Electric to thermal Sound to radiant A call is received on a cell phone. Potential to kinetic An object falls to the ground. Electric to radiant to electric What do you think Reread the statements at the beginning of the lesson. Fill in the After column with an A if you agree with the statement or a D if you disagree. Did you change your mind? to kinetic ConnectED Food is digested to help a person move. 3. Explain one concept you learned from the sentences that you highlighted. Log on to ConnectED.mcgraw-hill.com and access your textbook to find this lesson s resources. END OF LESSON Reading Essentials and Resources 87

Introduction to Forms of Energy

FORMS OF ENERGY LESSON PLAN 2.1 Introduction to Forms of Energy This lesson is designed for 3rd 5th grade students in a variety of school settings (public, private, STEM schools, and home schools) in the