1. Energy
Chapters 3 & 4

2. Objectives Recognize how energy causes change.
Describe common forms of energy.
Illustrate that the two general types of energy are kinetic energy and potential energy.

3. Different Forms of Energy Have Different Uses
Energy takes on many forms.
Lamps use electrical energy while plants use energy from the sun to grow.

4. Energy: ability to cause change (4)
All forms of energy have one important point in common--- they cause change to occur.
The flow of electrical energy through a wire causes a cool, dark bulb to get hot and glow.
You are a source of energy that makes changes in your environment!

5. What in this picture is using energy?

6. Forms of Energy (6) Mechanical Energy Sound Energy Chemical Energy
Thermal Energy
Electromagnetic Energy
Nuclear Energy

7. Mechanical Energy Energy that moves objects is mechanical energy.
The energy that you use to put book on a shelf is mechanical energy, s is energy that a person uses to turn car key.

8. Sound Energy Vibrations of particles
When you hear a car drive by, you are detecting vibrations in the air produced by sound energy.
Cannot travel through empty space.

9. Chemical Energy
Energy that is stored in chemical compositions of matter.
Example: When wood or gasoline burns, chemical energy produces heat.
The energy used by your body cells comes from chemicl energy.

10. Thermal Energy
The total amount of energy from the movement of particles in matter is thermal energy.
The energy of this motion in an object is the object’s thermal energy.

11. Electromagnetic Energy (13)
Transmitted through space in the form of electromagnetic waves.
Include visible light, x-rays, and microwaves.
The sun releases a large amount of electromagnetic energy, some of which is absorbed by Earth.

12. Nuclear Energy (14)
The center of an atom– it’s nucleus– is the source of nuclear energy.
When a heavy atom’s nucleus breaks apart or when the nuclei of two small atoms join together, energy is released.

13. Nuclear Energy
Everything has a beginning, and nuclear energy is no exception. The first reactor to use nuclear energy was built in The discovery of fission, that lead to nuclear energy, was discovered a few years earlier. A man named Enrico Fermi first discovered fission. In 1934, Fermi proved that neutrons could split atoms. This was breaking news. The particles made by these splits were lighter than the original atom. Later the scientist added up the particles, and still it weighed less than the original product. This proved that Einstein's theory was right, that some of the mass changed to energy. This theory was none other than e=mc2. The uses of this energy would be great. From cities, to ships, to bombs, nuclear energy powers them all.

14. Kinetic Energy The energy of motion is called Kinetic energy. (16)
Kinetic energy increases as mass increases. (17-18)
For example is a bowling ball and a soccor ball were moving at the same speed, the bowling ball would have more kinetic energy because of its greater mass.

15. Kinetic Energy Kinetic energy increases as speed increases.
If two identical bowling balls were rolling along at different speeds, the faster one would have more kinetic energy because of its greater speed.

16. Potential Energy
Potential Energy is the stored energy that an object has due to its position or chemical composition. (19) P
EX) energy stored in food (chemical energy) is also potential energy (22)

17. Review
Give three ways you use energy. How does each example involve a change?
What two factors determine an object’s kinetic energy?

18. 3.2 & 3.3 Objectives You will learn
How energy can be converted from one form to another
About the law of conservation of energy
How energy conversions may be inefficient
How technology can improve energy conversions

19. Energy can change forms but is NEVER Lost!
Potential energy is stored in the chemicals on the head of a match. The flame of a burning match releases that energy as light and heat. Where does the energy to strike the match come from in the first place.

20. Energy Changes Forms
Matches chemical energy stored can be changed to light and heat.
Photosynthesis
Page 78

21. Conversions between Potential Energy and Kinetic Energy
Potential energy can be changed into kinetic energy and back into potential energy.
Page 79

22. Using Energy Conversions
Page 80-81

23. Energy is Always Conserved
As the soccer ball rolls, it rubs against the ground. Some kinetic energy changes into heat because of friction. (30)
Some of the ball’s energy changes to sound energy as you hear the ball roll.
Although the ball loses kinetic energy, the overall amount of energy in the universe does not decrease.

24. Energy is Always Conserved
In the soccer ball, the ball loses energy, but this energy is transferred to other parts of the universe. Energy is conserved.
The Law of Conservation of Energy- states that energy can neither be created nor destroyed. (29)
Balance of Energy

25. Energy Conversions may produce unwanted forms of energy
When energy changes forms, the total amount of energy is conserved.
However, the amount of useful energy is almost always less than the total amount of energy.

26. Energy Efficiency
Energy Efficiency is a measurement of usable energy after an energy conversion. (32)
Example: Energy-efficient house-hold appliances. These appliances convert a greater percentage of energy into the desired form than inefficient forms.

27. Solar Cells
Made of several layers of light sensitive materials that convert sunlight directly into electrical energy (36)

28. Review
Describe an energy conversion you have observed in your own life.
What is the Law of Conservation of Energy?
Give an example of an energy conversion that produces unwanted forms of energy.

29. Chapter 4
Temperature and Heat

30. All Matter is Made of Moving Particles
All matters is made up of atoms, and atoms are always in motion, even if the objects themselves do not change their position.
The motion of these tiny particles gives the object energy.

31. The Kinetic Theory of Matter
The Kinetic Theory of Matter states that all of the particles that make up matter are constantly in motion.
Solid: Particles in solids are held tightly together but are always in motion.
Liquid: Particles in liquids slide by one another and are always in motion.
Gas: Particles in gases are completely free to move and are always in motion.

32. Temperature and Kinetic Energy
Particles move at different speeds have different kinetic energies
Temperature is a measure of the average kinetic energy of all the particles in an object. (45)
Particles Move Fast Particles Move Slow

33. Temperature and Kinetic Energy
We experience the connection between temp. and energy everyday.
For example: On a cold day, you warm your hands by putting them near a fire. The added energy makes the particles in your hand move faster.

34. Temperature Measured
In two common scales, temperature is measured in units called, degrees (°)
Farenheit: 32°- Freezing; 212°- Boiling
Celsius: 0°C- Freezing; 100°C- Boiling
A thermometer is used to measure temperature (48)

35. Liquid Thermometers
Liquid-filled thermometers measure how much the liquid expands in a narrow tube as the temperature increases.
Mercury is dangerous to handle so many thermometers today are filled with alcohol instead.
Alcohol expands evenly as temperatures increase & contracts evenly when temperatures decrease (add)

36. Thermal Expansion
The property that makes liquid-filled thermometers work is called thermal expansion.
Example: Construction engineers often have to take thermal expansion into account because steel and concrete both expand with increasing temperature. (49)
The Gateway Arch p. 108

37. Why does water warm up so slowly?
As Compared with
Butter and Oil?
Because more energy
Is needed!

38. Heat is Different from Temperature
Do Not Confuse the them!
Temperature is the measure of the average kinetic energy of all the particles in an object.
HEAT: flow of energy from higher to lower temperature (51)

39. Flow of Energy
Ice Cube in a bowl- At first different temperatures then they have the same temperature.
Energy flows from the particles in the warmer bowl to the particles in the cold ice and, later, the cooler water.
If energy flowed the opposite direction—from cooler to warmer---the ice would get colder in the bowl and bowl would get hotter!
THAT NEVER HAPPENS!

40. Thermal Energy
When energy flows from a warmer object to a cooler object, the thermal energy of both of the objects changes.
Thermal Energy- the total random kinetic energy of particles in an object.

41. Measuring Heat
The most common unit of heat measurement are the calorie and the joule
One calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1°C. (54)
The joule (J) is the standard scientific unit in which energy is measured.
One calorie is equal to 4.18 joules.

42. Calorie or calorie?
Calorie with a big “C” is referring to nutrition. It is actually one kilocalorie or 1000 calories.
This means that 1 Calorie in food contains enough energy to raise the temperature of 1 kilogram of water by 1°C.
So, each Calorie in food contains 1000 calories of energy.

43. Calorimeter How do we know how many Calories are in a food?
We use a calorimeter to see how much energy is released through heat.

44. Some Substances Change temperature more easily than others

45. Specific Heat
The amount of energy required to raise the temperature of 1 gram of a substance by 1°C is the specific heat value. (57)
So, each substance absorbs a different amount of energy in order to show the same increase in temperature.
Page 113 (Graph)

46. Do You Know?
1) Which of these substances has the highest specific heat?
     (a) Sample A
     (b) Sample B
     (c) Sample C
     (d) Sample D
Answer: A

47. Specific Heat and Mass Thermal energy depends on the object’s mass.
Which mass of water has more thermal energy?

48. Review How is temperature related to heat?
Heat transfers energy because a temperature difference exist.
What units do we use to measure heat?
Calorie and Joule
Describe specific heat
The amount of energy that 1 gram of a substance needs to absorb to increase in temperature by 1°C.

49. Energy Moves as Heat in Three Ways
Conduction
Convection
Radiation

50. Conduction
The process that moves energy from one object to another when they are touching physically.

51. Conductors (60)
Some materials transfer the kinetic energy of particles better than others.
Conductors are materials that transfer energy easily.
The pot handle is a poor conductor

52. Insulators (61)
Materials that conduct heat slowly or poorly are called insulators
Glass, wood, plastic and rubber are poor conductors (good insulators)
Nearly all liquids including water are poor conductors (good insulators)
Gases, including air are poor conductors,e.g., wool feels warm because it traps a lot of air
A fridge has insulation material round it to keep it cold – reduces amount of heat conducted to inside from the warmer room

53. Convection (60)
Convection is the movement of gases or liquids from a cooler spot to a warmer spot. If a soup pan is made of glass, we could see the movement of convection currents in the pan. The warmer soup moves up from the heated area at the bottom of the pan to the top where it is cooler. The cooler soup then moves to take the warmer soup's place. The movement is in a circular pattern within the pan (see picture above).

55. Convection Cycle
1. Warmer, less dense air is pushed up by cooler, denser air.
2. When air cools, it becomes more dense and starts to sink.
3. Sinking air moves under warmer air, pushing it upward.

56. Radiation (60)
The energy that travels as electromagnetic waves which include visible light, microwaves, and infrared light.
When radiation from the Sun is absorbed, energy is transferred through heat.

57. Insulators
Energy is always being transferred between objects at different temperatures.
Insulators are used to control and slow the transfer of energy from warmer to cooler objects.
Insulators work by trapping the energy.

58. Insulators

59. Heat Transfer
Conduction: energy moves from one object to another by physically touching
Convection: energy transfers by the movement of large numbers of particles in the same direction with in a liquid or gas
Radiation: energy that travels through electromagnetic wave
Insulator: poor conductors

60. 4.3 Review What are 3 ways energy can be transferred through heat?
Convection, conduction, radiation
How are conductors and insulators different?
Conductors easily transfer energy, but insulators do not.