1. Chapter 9 Energy: Forms and Changes Section 1: What is Energy?

2. Essential questions  What is the relationship between energy and work?  What is the difference between kinetic and potential energy?  Identify the different forms of energy and tell about each one.

3. Nature of Energy EEnergy is all around you! You can hear energy as sound. You can see energy as light. And you can feel it as wind.

4.  You use energy when you: hit a softball. lift your book bag. compress a spring.

5. Nature of Energy Living organisms need energy for growth and movement.

6. Nature of Energy  Energy is involved when: a bird flies. a bomb explodes. rain falls from the sky. electricity flows in a wire.

7. Nature of Energy  What is energy that it can be involved in so many different activities? Energy can be defined as the ability to do work. If an object or organism does work (exerts a force over a distance to move an object) the object or organism uses energy.

8. Nature of Energy  Because of the direct connection between energy and work, energy is measured in the same unit as work: joules (J).  In addition to using energy to do work, objects gain energy because work is being done on them.

9. States of EnergyStates of Energy: Kinetic and Potential Energy  Kinetic Energy is the energy of motion.  Potential Energy is stored energy.  Mechanical energy is potential energy + kinetic energy.

10. KineticKinetic Energy  The energy of motion is called kinetic energy.  The faster an object moves, the more kinetic energy it has.  The greater the mass of a moving object, the more kinetic energy it has.  Kinetic energy depends on both mass and velocity.

11. Kinetic Energy  Kinetic Energy = mass times velocity squared divided by two K.E. = mass x velocity 2 What has a greater affect on kinetic energy, mass or velocity? Why?

12. PotentialPotential Energy  Potential Energy is stored energy. Stored chemically in fuel, the nucleus of atom, and in foods. Or stored because of the work done on it:  Stretching a rubber band.  Winding a watch.  Pulling back on a bow’s arrow.  Lifting a brick high in the air.

13. Types of Potential EnergyPotential Energy  There are 3 types of Potential Energy Gravitational Elastic Chemical

14. Gravitational Potential Energy  Potential energy that is dependent on height is called gravitational potential energy.

15. Gravitational Potential Energy  A waterfall, a suspension bridge, and a falling snowflake all have gravitational potential energy.

16. Gravitational Potential Energy  If you stand on a 3-meter diving board, you have 3 times the G.P.E, than you had on a 1-meter diving board.

17. Gravitational Potential Energy  “The bigger they are the harder they fall” is not just a saying. It’s true. Objects with more mass have greater G.P.E.  The formula to find G.P.E. is G.P.E. = Weight X Height.

18. Elastic Potential Energy  Energy that is stored due to being stretched or compressed is called elastic potential energy.

19. Chemical Energy  Chemical Energy is required to bond atoms together.  And when bonds are broken, energy is released.  Chemical energy is a form of potential energy because it depends on the position and arrangement of atoms. Chemical energy

20. Chemical Energy  Fuel and food are forms of stored chemical energy.

21. Mechanical Energy  When work is done to an object, it acquires energy. The energy it acquires is known as mechanical energy.  Mechanical energy = potential energy + kinetic energy

22. Mechanical Energy  When you kick a football, you give mechanical energy to the football to make it move.

23. Mechanical Energy When you throw a bowling ball, you give it energy. When that bowling ball hits the pins, some of the energy is transferred to the pins (transfer of momentum).

24. Forms of Energy  The other main forms of energy are: Thermal (heat) Electrical Sound Light Nuclear

25. Thermal Energy  The internal motion of the atoms is called thermal energy, because moving particles produce heat.  Heat energy can be produced by friction. Faster the particles move, the more kinetic energy and the more heat they produce.  Heat energy causes changes in temperature and phase of any form of matter.

26. Electrical Energy  Power lines carry electromagnetic energy into your home in the form of electricity.  Electrical energy is the energy of moving electrons.  Electrons are negatively charged particles of atoms.

27. Sound Energy  Sound energy is caused by a vibrating object.  The vibrations are transferred through the air to your ear and your ear deciphers it.

28. Light Energy  Light is a form of electromagnetic energy.  Light energy is produced by the vibrations of electrically charged particles.  Each color of light (Roy G BIV) represents a different amount of electromagnetic energy.  Electromagnetic Energy is also carried by X-rays, radio waves, and laser light.

29. Nuclear Energy  The nucleus of an atom is the source of nuclear energy.

30. Nuclear Energy  When the nucleus splits (fission), nuclear energy is released in the form of heat energy and light energy. Power plants use fission to generate electrical energy.  Nuclear energy is also released when nuclei collide at high speeds and join (fusion).

31. Nuclear Energy The sun’s energy is produced from a nuclear fusion reaction in which hydrogen nuclei fuse to form helium nuclei. The sun’s heat and light come from fusion.

32. Nuclear Energy  Nuclear energy is the most concentrated form of energy.

33. Chapter 9 Energy: Forms and Changes Section 2: Energy Conversions

34. Essential Questions  What is an energy conversion?  What are some examples of energy conversion for the different forms of energy?  How can energy conversions make energy useful?  What is the role of machines in energy conversions?

35. Energy Conversion  Energy can be changed from one form to another. These changes are called energy conversions.

36. Energy conversions  All forms of energy can be converted into other forms. The sun’s energy through solar cells can be converted directly into electricity. Green plants convert the sun’s energy (electromagnetic) into starches and sugars (chemical energy).

37. States of EnergyEnergy  Most often, the conversion is between potential and kinetic energy.  All forms of energy can be in either of two states: Potential Kinetic

38. Kinetic-Potential Energy Conversion Roller coasters work because of the energy that is built into the system. Initially, the cars are pulled mechanically up the tallest hill, giving them a great deal of potential energy. From that point, the conversion between potential and kinetic energy powers the cars throughout the entire ride.ride

39. Kinetic vs. Potential EnergyEnergy At the point of maximum potential energy, the car has minimum kinetic energy.

40. Kinetic-Potential Energy Conversions  As a basketball player throws the ball into the air, various energy conversions take place.

41. Ball slows down Ball speeds up

42. Conversions Involving Chemical Energy  Chemical energy comes from the food you eat.  Your body uses chemical energy to function.

43. Energy Conversions in Living Things  Photosynthesis uses the sun’s light energy to create chemical energy for the plant. Photosynthesis  In this way, light energy is changed into chemical energy.  When you eat, that chemical energy is converted into kinetic energy for you to use.

44. Other energy conversionsconversions In an electric motor, electromagnetic energy is converted to mechanical energy. In a battery, chemical energy is converted into electromagnetic energy. The mechanical energy of a waterfall is converted to electrical energy in a generator.

45. Energy Conversions  In an automobile engine, fuel is burned to convert chemical energy into heat energy. The heat energy is then changed into mechanical energy.

46. Chemical  Heat  Mechanical

47. Who cares?  Energy conversions are needed for everything we do.

48. Energy and Machines  Machines make work easier by changing the size or direction of force.  Some machines change the energy put into them into other kinds of energy.

49. Review for fun!  Roller coaster energyenergy

50. Chapter 9 Energy: Forms and Changes Section 3: Conservation of Energy

51. Essential Questions  How is energy conserved in a closed system?  What is the law of conservation of energy?  What are some examples of how thermal energy is always a result of energy conversion?  Why is perpetual motion impossible?

52. The Law of Conservation of EnergyLaw of Conservation of Energy  Energy can be neither created nor destroyed by ordinary means. It can only be converted from one form to another. If energy seems to disappear, then scientists look for it – leading to many important discoveries.

53. Where Does the Energy Go?  Energy can not be lost.  Roller coaster example: Some of the potential and kinetic energy is released as thermal energy because of FRICTION

54. A Closed System  A closed system – a group of objects that transfer energy only to each other  If all types of energy are added up, you can see none is lost, just changed

55. Law of Conservation of EnergyEnergy  Energy cannot be created or destroyed.  The total amount of energy in a closed system is always the same.  Any number of conversions could take place, though.

56. Thermal Energy  Any time an energy conversion takes place, some is converted to thermal energy. This is why there is no such thing as perpetual motion.  This thermal energy is due to FRICTION.

57. Energy Efficiency  Energy efficiency is a comparison before and after conversion  Energy conversions that waste less energy are efficient  Aerodynamic cars are an example

58. Chapter 9 Energy: Forms and Changes Section 4: Energy Resources

59. Essential Questions  What are some energy resources?  How is the sun the source of most energy on Earth?  What are the advantages and the disadvantages of using various energy resources?

60. Energy resources  Energy resources are natural resources that can be converted into other forms of energy to do work.  Non-renewable resources cannot be replaced or can only be replaced very slowly.

61. Fossil Fuels  Fossil fuels – energy resources formed from buried plant and animal remains millions of years old.  Nonrenewable resources: petroleum (gasoline, plastics, etc); natural gas; coal

62. Electrical Energy from Fossil Fuels  Fossil fuels are the main source of electrical energy in the U.S.  Electrical generators convert a fossil fuels’ chemical energy into electrical energy  Fossil fuels are burned, thermal energy turns water to steam, steam converts to kinetic energy by powering a turbine, creating electricity

63. Nuclear Energy  Like fossil fuel power plants, nuclear power plants use thermal energy, using steam  Nuclear energy is generated from radioactive elements  Nuclear fission occurs when nuclei of atoms are split into smaller nuclei, releasing nuclear energy  Non-renewable resource

64. Renewable Resources  Renewable resources are replaced faster than they are used. Solar energy (solar cells) Hydroelectric energy (water-produced) Wind energy (wind turbines) Geothermal energy (thermal energy caused by the heating of the Earth’s crust) Biomass (organic matter burned to release energy)

66. Non-renewable vs. renewable  Both have advantages and disadvantages  Copy and study the table on page 262 of the classroom textbook.