1. Physical Science Chapter 4, Section 1
The Nature of Energy
Physical Science Chapter 4, Section 1

2. What is energy?
Every change that occurs- large or small- requires energy.

3. Change Requires Energy
When something is able to change its environment or itself, it has energy.
Energy is the ability to change.
Anything that causes change must have energy.

4. Different Forms of Energy
THINK: What happens when you turn on a light bulb? What happens when you turn on a CD player?
In both situations, energy moves from one place to another.
Both of these situations are different from one another because there are different forms of energy.

5. Different Forms of Energy
There are 4 different forms of energy:
Electrical
Ex: using a toaster in the morning
Chemical
Ex: stored in food
Radiant
Ex: from the Sun to warm the Earth
Thermal
Ex: HEAT!

6. An Energy Analogy
Please read “An Energy Analogy” on page 101.

7. Kinetic Energy
When you think of energy, you think of action, or objects in motion!
This is kinetic energy: the energy a moving object has because of its motion.
The kinetic energy of a moving object depends on the object’s mass and its speed.

8. Kinetic Energy Equation

9. Joule
The SI unit of energy is the joule or J.

10. Potential Energy Not all energy involves motion.
Motionless object contain energy!
The object has the POTENTIAL to cause change.
Potential energy: stored energy due to position.
If an object moves, its stored energy is converted to energy of motion.

11. Elastic Potential Energy
THINK: What happens when you stretch a rubber band and then let it go? What types of energy are in play?
Elastic Potential Energy: is energy stored by something that can stretch or compress, such as a rubber band or spring.

12. Chemical Potential Energy
THINK: How do we, as humans, get energy?
Chemical potential energy: energy stored in chemical bonds.
Energy is stored in the bonds that hold the carbon and hydrogen atoms together and is released when the gas is burned.

13. Gravitational Potential Energy
Anything that can fall has stored energy called gravitational potential energy.
Gravitational potential energy (GPE): energy stored by objects due to their position above Earth’s surface.
The GPE of an object depends on the object’s mass and height above the ground.

14. Gravitational Potential Energy
GPE= mass(kg) x acceleration of gravity(m/s2) x height (m)
On Earth, the acceleration of gravity is 9.8m/s2.

15. Changing GPE
THINK: Looking at the picture, which of the following diving boards would give a diver the most GPE? WHY???
Remember the equation!

16. Changing GPE THINK: What about these diving boards?
How could one diver have more GPE than another?
Remember the equation!

17. Conservation of Energy
Physical Science Chapter 4, Section 2

18. Transforming Electrical Energy
You use many devices every day that convert one form of energy to other forms.
Think about the lights in this room. What are they doing at this moment?

19. Transforming Chemical Energy
Fuel stores energy in the form of chemical potential energy
The engine of a car transforms the chemical potential energy stored in gasoline molecules into the kinetic energy of a moving car.
The burning fuel produces thermal energy.
Thermal energy causes gases to expand and move parts of the car, producing kinetic energy.

20. Transforming Chemical Energy
Some energy transformations are less obvious because they do not result in visible motion, sound, heat, or light.
Every green plant you see converts light energy from the Sun into energy stored in chemical bonds in the plant.
You eat the plant and the chemical potential energy is transformed into other forms of energy by your body.

21. Conversions between Kinetic and Potential Energy
Mechanical energy: the total amount of potential and kinetic energy in a system and can be expressed by this equation:
Mechanical nrg= potential nrg + kinetic nrg
Mechanical energy is energy due to the position and the motion of an object or the objects in a system.

22. Falling Objects
THINK: Look at the picture. Describe the types of energy in play.
What happens when one of the apples falls?
Refer to page 109 if you need help.

23. Energy Transformations in Projectile Motion
Energy transformations also occur during projectile motion when an object moves in a curved path.
Think about the game of baseball.
In this picture, where would the baseball have the most GPE?

24. Energy Transformations in a Swing
THINK: Describe the energy of a person in a swing.

25. The Law of Conservation of Energy
Kinetic and potential energy change forms and no energy is destroyed.
THIS IS ALWAYS TRUE!!!!
Energy can change from one form to another, but the total amount of energy never changes.
The Law of Conservation of Energy: states that energy cannot be created or destroyed.

26. Conserving Resources
THINK: How many times do your parents tell you to conserve energy by turning of the lights when you leave a room? Why would they ask you to do this?
The law of conservation of energy is a universal principle that describes what happens to energy as it is transferred from one object to another or as it is transformed.

27. Is energy always conserved?
THINK: What happens when you no longer pedal your bicycle on a flat road? Why do you not stay at a constant motion?

28. The Effect of Friction
Thinking of the swing again, what happens when you no longer pump on the swing? Why does this occur?

29. Converting Mass into Energy
THINK: How does the Sun unleash enough energy to light and warm Earth from so far away?
A special kind of energy conversion – nuclear fusion – takes place in the Sun and other stars.
During this process a small amount of mass is transformed into a tremendous amount of energy.

30. Nuclear Fission
Another process involving the nuclei of atoms, called nuclear fission, converts a small amount of mass into enormous quantities of energy.
In both processes, fusion and fission, mass is converted to energy.
The process of nuclear fission is used by nuclear power plants to generate electrical energy.

31. The Human Body: Balancing the Energy Equation
THINK: What forms of energy can be found in the body right now?

32. Energy Conservation in Your Body
The complex chemical and physical processes going on in your body also obey the law of conservation of energy.
Your body stores energy in the form of fat and other chemical compounds.
Stored chemical potential keeps you alive.
Your body also converts this energy to heat that is transferred to your surroundings, and you use this energy to make your body move.
To maintain a healthy weight, you must have a balance between energy contained in the food you eat and the energy your body uses.