Energy Transformations

1. Energy Transformations

2. What is energy? • Energy is the capacity to do work or produce heat.

3. Two Types of Energy • Potential Energy-stored energy and the energy of position • Kinetic Energy-working energy in motion

4. Forms of Energy • Chemical energy • Electrical energy • Nuclear energy • Mechanical energy • Thermal energy • Light energy • Sound energy • Gravitational energy

5. Chemical Energy • Chemical energy is the energy stored in the bonds of atoms and molecules. • Chemical energy is potential energy.

6. Electrical Energy • Electrical energy is delivered by tiny charged particles called electrons, typically moving through a wire. • Electrical energy is kinetic when the current is flowing. • Electrical energy is potential when the circuit is open and the current is not flowing.

7. Nuclear Energy • Nuclear energy is energy stored in the nucleus of an atom and is the energy that holds the nucleus together. • Nuclear energy is potential energy.

8. Mechanical Energy • Mechanical energy can be both potential and kinetic. • When potential: Mechanical energy is the energy stored in objects by tension (stretched rubber bands). • When kinetic: Mechanical energy is the energy stored in the movement of objects (hammering a nail).

9. Thermal Energy • Thermal energy is heat, the vibration and movement of the atoms and molecules within a substance. • Thermal energy is kinetic energy.

10. Radiant Energy • Light energy • Moves in waves • Radiant/light energy is kinetic energy.

11. Sound Energy • Sound energy is the movement of energy through substances in waves. Sound is produced when a force causes an object to vibrate. • Sound energy is kinetic energy.

12. Gravitational Energy • Gravitational energy is the energy an object possesses because of its position in a gravitational field. • Gravitational energy is a form of potential energy.

13. Energy Transformations • In the world around you, energy is transforming continually between one form and another.

14. Changing Forms of Energy • Forest fires are a dramatic example of an environmental change that can occur naturally as a result of lightning strikes.

15. Tracking Energy Transformations • As the mountain biker pedals, his leg muscles transform chemical energy into mechanical energy. • Mechanical energy of his leg muscles transforms into mechanical energy of the bicycle as he pedals.

16. Tracking Energy Transformations • Some of this energy transforms into potential gravitational energy as he moves up the hill. • Also, some energy is transformed into thermal energy. • His body is warmer because chemical energy is being released

17. Tracking Energy Transformations • Because of friction, the mechanical parts of the bicycle are warmer, too. • Thermal energy is almost always produced by an energy transformation.

18. Tracking Energy Transformations The energy transformations that occur when people exercise, when cars run, when living things grow and even when stars explode, all produce thermal energy.

19. Law of Conservation of Energy • Energy is never created or destroyed. • The only thing that changes is the form in which energy appears. • Example: When the biker is resting at the summit, all his original energy is still around. Some of the energy is in the form of potential gravitational energy, which he will use as he coasts down the hill. Some of this energy was changed to thermal energy by friction in the bike. Chemical energy was also changed to thermal energy in the biker’s muscles, making him feel hot As he rests, this thermal energy moves from his body to the air around him. No energy is missing--- it can all be accounted for.

20. Potential energy is converted into kinetic energy. • Before the yo-yo begins its fall it has stored energy due to its position. At the top it has its maximum potential gravitational energy. As it starts to fall the potential gravitational energy begins to be changed into kinetic mechanical energy. At the bottom its potential energy has been converted into kinetic energy so that it now has its maximum kinetic energy.

21. Potential energy is converted into kinetic energy. • A waterfall has both potential gravitational and kinetic mechanical energy. The water at the top of Bridal Veil Falls has stored potential energy. When the water begins to fall, its potential energy is changed into kinetic energy.

22. Energy Changes Form • A car engine burns gasoline, converting the chemical energy in gasoline into mechanical energy. Solar cells change radiant light energy into electrical energy. Energy changes form, but the total amount of energy in the universe stays the same.

23. Energy Changes Form Hybrid cars that use an electric motor and a gasoline engine for power are now available. Hybrid cars make energy transformations more efficient so the car can travel farther on a gallon of gas.

24. Energy Changes Form You wake up. It's a cool, sunny day, You think you'll go for a bike ride. But first you eat a good healthy breakfast. You are taking the chemical energy stored in food into your own body. Any time energy is stored, it's called potential energy. It's available for later use. Without you needing to think about it, the cells in your body will break down the chemical bonds in the food and release the energy in those bonds. You'll use the energy to stay warm, to grow, to keep your internal organs working, and to move your muscles.

25. Energy Changes Form And you are moving. You jump up from the table, grab a jacket, head out the door. You hop on your bicycle. The energy of motion is called kinetic/mechanical energy. As you pump your legs, the bicycle starts to roll. Your kinetic/mechanical energy is being transferred to the bicycle.

26. Energy Changes Form Back at home, you turn on a radio. It runs on electrical energy which travels along the wires that connect a power plant to your home. The electrical energy used by the radio is converted into sound energy. Sound is another form of kinetic energy--it's air in motion. You can move your muscles to make sound too. For example, you can hit a drum, sing or shout, or strum on a guitar. The guitar strings, vocal cords, or drumhead, once set in motion, make the air around them move.

27. Transforming Chemical Energy The matter contained in living organisms contains chemical energy. When organisms die, chemical compounds in their biomass break down. Bacteria, fungi, and other organisms help convert these chemical compounds to simpler chemicals that can be used by other living things.

28. Transforming Chemical Energy • Thermal energy also is released as these changes occur. • Example: A compost pile can contain plant matter, such as grass clippings and leaves. As the compost pile decomposes, chemical energy is converted into thermal energy. This can cause the temperature of a compost pile to reach 60° C.

29. Transforming Electrical Energy • Every day you use electrical energy. When you flip a switch, or turn on a radio or television, or use a hair drier, you are transforming electrical energy to other forms of energy.

30. Transforming Thermal Energy • Chemical energy changes into thermalenergy when something burns. • Electrical energy changes into thermalenergy when a wire that is carrying an electric current gets hot. • Thermal energy can be transformed into radiant energy such as when a bar of metal is heated to a high temperature, it glows and gives off light.

31. Generating Electrical Energy Every power plant works on the same principle---energy is used to turn a large generator. A generator is a device that transforms kinetic energy into electrical energy. In fossil fuel power plants, coal, oil, or natural gas is burned to boil water. As the hot water boils, the steam rushes through a turbine, which contains a set of narrowly spaced fan blades. The steam pushes on the blades and turns the turbine, which in turn rotates a shaft in the generator to produce the electrical energy.

32. Power Plants Almost 90 percent of the electrical energy generated in the U.S. is produced by nuclear and fossil fuel power plants. Other types of power plants include Hydroelectric and wind. Hydroelectric power plants transform the kinetic energy of moving water into electrical energy. Wind power plants transform the kinetic energy of moving air into electrical energy.

33. Quick Review • Changing Forms of Energy • Thermal energy is usually one of the forms of energy produced in energy transformations. • The law of conservation of energy states that energy cannot be created nor destroyed; it can only change form. • The total energy doesn’t change when an energy transformation occurs. • As an object rises and falls, kinetic and potential energy are transformed into each other, but the total energy doesn’t change.

34. Generating Electrical Energy • A generator converts kinetic energy into electrical energy. • Burning fossil fuels produces thermal energy that is used to boil water and produce steam. • In a power plant, steam is used to spin a turbine which then spins an electric generator.