1. Ch. 14: Energy

2. Energy = the ability to cause change in matter

3. Two Types of Energy
Potential Energy = energy that is due to the position or condition of an object
Example: a rock sitting at the top of a hill
Kinetic Energy = the energy of motion
Example: when the rock sitting at the top of a hill starts rolling down the hill

4. Potential vs Kinetic Energy
The more massive a non-moving object is, the more potential energy it has.
A large boulder sitting at the top of a hill has a lot more potential energy than a tiny pebble sitting at the top of a hill.
Potential vs Kinetic Energy

5. Potential vs Kinetic Energy
The faster an object is moving the more kinetic energy it has.
A car moving at 100 miles per hour has more kinetic energy than the same car moving at 50 miles per hour.
Potential vs Kinetic Energy

6. Types of Potential and Kinetic Energy
Electrical energy
Thermal energy
Sound energy
Radiant (light) energy
Chemical energy
Nuclear energy
Solar energy
Types of Potential and Kinetic Energy

7. Energy Transformations
Fireworks
Stored chemical energy in a rocket
Chemical reaction takes place and the energy shoots the rocket into the sky
The rocket explodes and chemical energy is transformed into light energy
A loud boom happens and light energy is transformed into sound energy
Energy can change from one form to another
Energy Transformations

8. Energy Transformations
Flashlight
Chemical potential energy is stored in a battery
When the flashlight is turned on, chemical energy transforms into electrical energy
Electrical energy is transformed into light energy
Light energy is transformed into thermal energy
Energy Transformations

9. Law of Conservation of Energy
The total amount of energy in a system is always the same
Energy cannot be created or destroyed
No energy can ever be lost
No energy can ever be gained
Energy only transforms
Law of Conservation of Energy

10. Wave = a disturbance that carries energy through matter or space
Waves

11. Mechanical wave = a wave that requires matter to travel through
Examples:
Waves in water
Waves in a spring
Earthquake waves
Mechanical Waves

12. Parts of a Wave Crest = highest point on a wave
Trough = lowest point on a wave
Wavelength = distance of a complete wave; crest to crest or trough to trough
Amplitude = height of a wave; height from trough to crest
Parts of a Wave

13. Sound Waves Different type of wave A sound wave is made up of:
Compressions of molecules in the air
Areas where the molecules are spread far apart
Sound Waves

14. Frequency = the number of vibrations of a sound wave per second
Measured in Hertz (Hz)
Most people can hear sounds that have frequencies between
20 – 20,000 Hz
Frequency

15. Pitch Sounds with a high pitch have a high frequency
Sounds with a low pitch have a low frequency
Pitch

16. Loudness Loudness of a sound wave is measured in decibels (dB)
Waves with a high amplitude are loud
Waves with a low amplitude are soft
Loudness

17. Light waves Light travels in waves that don’t need matter
Light waves make up the electromagnetic spectrum
Light waves

18. Electromagnetic Spectrum
Types of light
Infrared waves
Microwaves
Radio waves
Visible light
X rays
Ultraviolet light
Gamma rays
Electromagnetic Spectrum

19. Solar energy Energy from the sun warms:
Air
Land
Water
Causes air to flow and wind that moves weather systems
Causes the water cycle to occur
Solar energy

20. How light behaves Light travels in a straight line
Reflection = the bouncing of light off a surface
Example: light from the moon is really a reflection from the sun; the moon does not produce its own light
How light behaves

21. The amount of light that is reflected from an object depends on the surface of that object
A smooth surface (mirror) reflects almost all light
A rough surface (soil) reflects only some light; the rest is absorbed
Reflection

22. To us, visible light looks white, but it is really a bunch of colors together
Red
Orange
Yellow
Green
Blue
Indigo
violet
Visible light

24. When we see the color of an object, it is because that color is being reflected when all the other colors of the light are being absorbed.
A cucumber looks green because it reflects green light and absorbs all the other colors.
Visible light

25. Visible light A white object reflects almost all visible light
A black object absorbs almost all visible light
This is why wearing white clothes in the summer will keep you cooler than wearing black clothes.
Visible light

26. Occurs because speed of light is different through different materials
Light travels more slowly through dense materials
Light travels faster through air than it does through water
Refraction

27. Refraction = the bending of light as it passes from the surface of one material to another

28. Diffraction = the bending of light around the edge of an object

29. A transparent material allows most of the light to pass through it
Example: glass
Transparent

30. Translucent A translucent material allows some light to pass through
Examples:
Wax
Plastic
Translucent

31. Opaque materials don’t allow any light to pass through