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CHAPTER 3: ENERGY
CHAPTER 3.1: ENERGY EXISTS IN DIFFERENT FORMS
Different forms of energy have different uses:
Just about everything you see happening around you uses energy.
Lamps, Plants, Eating, Exercising, Reading, and Sitting…use energy
ALL FORMS OF ENERGY – CAUSES CHANGES TO OCCUR
ENERGY – IS THE ABILITY TO CAUSE CHANGE
FORMS OF ENERGY
1. MECHANICAL ENERGY –
 energy that moves objects
 EX: turn a car key, place a book on a shelf
2. SOUND ENERGY  Results from the vibration of particles in a solid, liquid, or gas
 Structures in the ear vibrate due to sound
 Hearing – detecting vibrations in the air produced by sound energy
 Sound cannot travel thru empty space
3. CHEMICAL ENERGY –
 Energy that is stored in the chemical composition of matter
 Amount of CE depends on types and arrangement of atoms in substance
 When wood or gasoline burns – CE produces heat
 Energy in cells comes from the foods that you eat – FOOD ENERGY
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CHAPTER 3: ENERGY
4. THERMAL ENERGY –
 Total amount of energy from the movement of particles in matter
 Atoms and molecules are always moving
 Energy in this motion in an object is its TE
5. ELECTROMAGNETIC ENERGY
 Energy that is transmitted thru space in the form of electromagnetic waves
 EE can travel thru empty space
 Include: visible light, x-rays, microwaves
 X-rays – high energy to look at bones
 Microwaves – less energy that x-rays – cook food or transmit cellular calls
 Sun releases large amounts
6. NUCLEAR ENERGY –
 Center of the atom – Nucleus – is the source
 Large amount of energy holds the nucleus together
 When a heavy atom’s nucleus breaks apart or two smaller join- energy released
 NE released from the fusing of small nuclei to form larger - keeps Sun burning
NAME OTHER FORMS OF ENERGY……
SHOW CONSERVATION OVERHEAD
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CHAPTER 3: ENERGY
Kinetic energy and potential energy are the two general types of energy
KINETIC ENERGY VS. POTENTIAL ENERGY
KINETIC ENERGY –
 Means “related to motion”
 Depends on object’s MASS and SPEED of object
 KE increases as mass increases1) bowling ball and soccer ball moving, bowling ball has more KE
 KE increases as speed increases
1) if two identical bowling balls are rolling at different speed – one
moving the fastest would have more KE
POTENTIAL ENERGY –
 STORED energy due to POSITION or CHEMICAL composition
 Ball in hand is in a position to move
 GRAVITY – form of PE
 Chemical PE comes from the atoms it contains (Food) and when atoms are
rearranged they release energy
 Bow or rubber band being stretched – has PE – when let go PE released
 Rocket fuel also has chemical energy – atoms are rearranged PE released
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CHAPTER 3: ENERGY
DO SECTION REVIEW 1-6 PAGE 76
THINK SCIENCE –(GROUP) PAGE 77
What might be the advantages if all future cars were electric powered?
(Smog and pollution would decrease)
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CHAPTER 3: ENERGY
CHAPTER 3.2: ENERGY CAN CHANGE FORMS BUT IS NEVER LOST
THINK ABOUT: How does energy change form?
PE is stored in the chemical on the head of a match.
The flame of a burning match releases the energy as light and heat.
Where does the energy to strike the match come from in the first place?
ENERGY CHANGES FORM
Before the chemical energy in the match changes form, energy conversions must take
place
Plants convert Sun energy into chemical (sugar) energy – which you eat and release
This chemical energy is converted to KE when you strike the match
Friction between match and surface produces heat – heat provides energy for chemical
change
Chemical change produces a flame….a total of 5 energy conversions
Conversions between PE and KE
See Figure page 79
1) At first, the ski jumper is at the top of the hill. PE due to gravity
2) As the ski jumper starts moving downhill, PE changes to KE which moves jumper
downhill
3) When the ski jumper takes off from ramp, some of KE changes back to PE
4) When ski jumper descends to the ground, PE changes to KE
5) When skier lands and stops moving, All PE
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CHAPTER 3: ENERGY
QUESTIONS:
 Why does the ski jumper have PE?
 At the top, he has PE due to gravity
 Why is some of the PE converted to kinetic in step 2?
 The skier has descended and moves faster as a result. KE is motion energy
 When does the ski jumper have the most PE after he takes off from the
jump?
 At the skier’s point of greatest height
 Why does the ski jumper’s PE increase for a short time after taking off
from the jump?
 Because his height above the ground increases
 How could another ski jumper have a greater amount of PE than one
shown?
 Start from a greater height, have a greater mass
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CHAPTER 3: ENERGY
USING ENERGY CONVERSIONS
READ PAGE 80 AND LOOK AT DIAGRAM ON PAGE 81
ENERGY IS ALWAYS CONSERVED
Law of Conservation of Energy: Energy cannot be created or destroyed, it just changes form
EX: soccer ball’s KE decreases as the energy is converted to heat and sound
ENERGY CONVERSIONS MAY PRODUCE UNWANTED FORMS OF ENERGY
Amt of USEFUL energy is almost always less than the amt of energy
EX: FAN – amt of electrical energy used is greater than KE of blades
- Sound and Heat also produced
ENERGY EFFICIENCY – measurement of usable energy after an energy conversion
- EE appliances convert a greater % into the desired form than inefficient ones
- Less elec energy is needed to operate EE appliances
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CHAPTER 3: ENERGY
Kinetic energy and potential energy are the two general types of energy
KINETIC ENERGY VS. POTENTIAL ENERGY
KINETIC ENERGY –
 Means “related to _________”
 Depends on object’s _______ and __________ of object
 KE ____________as mass increases2) bowling ball and soccer ball moving, bowling ball has more KE
 KE ___________ as speed increases
2) if two identical bowling balls are rolling at different speed – one
moving the fastest would have more KE
POTENTIAL ENERGY –
 STORED energy due to __________or _____________composition
 Ball in hand is in a position to move
 GRAVITY – form of PE
 Chemical PE comes from the atoms it contains (Food) and when atoms are
rearranged they release energy
 Bow or rubber band being stretched – has PE – when let go PE released
 Rocket fuel also has chemical energy – atoms are rearranged PE released
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CHAPTER 3: ENERGY
DO SECTION REVIEW 1-6 PAGE 76
1.
2.
3.
4.
5.
6.
THINK SCIENCE –(GROUP) PAGE 77
What might be the advantages if all future cars were electric powered?
______________________________________________________________
_______________________________________________________________
_______________________________________________________________
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CHAPTER 3: ENERGY
CHAPTER 3.2: ENERGY CAN CHANGE FORMS BUT IS NEVER LOST
THINK ABOUT: How does energy change form?
PE is stored in the chemical on the head of a match.
The flame of a burning match releases the energy as ____ and _____.
Where does the energy to strike the match come from in the first place?
_______________________________________________________________
ENERGY CHANGES FORM
Before the chemical energy in the match changes form, energy conversions must take
place
Plants convert _____ energy into ________ (sugar) energy – which you eat and release
This chemical energy is converted to KE when you strike the match
Friction between match and surface produces heat – heat provides energy for chemical
change
Chemical change produces a flame….a total of 5 energy conversions
Conversions between PE and KE
See Figure page 79
6) At first, the ski jumper is at the top of the hill. ____ due to gravity
7) As the ski jumper starts moving downhill, ____ changes to____ which moves
jumper downhill
8) When the ski jumper takes off from ramp, some of ___changes back to ___
9) When ski jumper descends to the ground, ___ changes to___
10)When skier lands and stops moving, All ____
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CHAPTER 3: ENERGY
QUESTIONS:
 Why does the ski jumper have PE?
 Why is some of the PE converted to kinetic in step 2?
 When does the ski jumper have the most PE after he takes off from the
jump?
 Why does the ski jumper’s PE increase for a short time after taking off
from the jump?
 How could another ski jumper have a greater amount of PE than one
shown?
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