Transcript Chapter 3.1
Chapter 3.1
Energy exists in different forms
Energy
All forms of energy cause changes to occur
Wind causes flag to flutter
Light bulb gets hot and glows
You pick up a tennis racket, change position
Hit tennis ball
The ability to cause a change
Energy takes many different forms and has
many different effects.
Forms of Energy
Scientist classify energy into many forms pg 73
Mechanical Energy
Sound Energy
Chemical Energy
Thermal Energy
Electromagnetic Energy
Nuclear Energy
Each form causes change in a different way.
Mechanical Energy
Energy that moves objects
Example
Energy
used to put a book on a shelf
Energy used to turn a key
Sound Energy
Sound results from the vibration of particles
in a solid, liquid or gas
Sound cannot travel through empty space
Chemical Energy
Energy that is stored in the chemical
composition of matter
Amount of energy
Depends on types of atoms
Depends on arrangement of atoms
Examples
When wood or gasoline burns chemical energy produces
heat
Cells use chemical energy that our bodies store from the
food we eat
Thermal Energy
Total amount of energy from the movement
of particles in matter
Energy of the motion of atoms and molecules
Electromagnetic Energy
Energy transmitted through space in the
form of electromagnetic waves
Can travel through empty space
These waves include
Visible light
X-rays
Microwaves
Sun releases large amount that is
absorbed by Earth
Nuclear Energy
The center of an atom, its nucleus, is the
source of nuclear energy
When a heavy atoms nucleus breaks apart
energy is released
When the nuclei of two small atoms join
together energy is released
General Types of Energy
All forms of energy can be described in
terms of two general types of energy
Kinetic Energy – energy of motion
Increases
as mass increases
Increases as speed increases
Potential Energy – stored energy
Due
to position (pg 76)
Gravity, stretching, compressing
chemical
composition
Energy stored in food, fuel in rocket engine
Potential and Kinetic Energy demonstration
Chapter 3.2
Energy can change forms but is never lost
Energy Changes Form
How does energy change form?
Example – a match
PE
is stored in the chemicals on the head of the match
The flame releases that energy as light and heat
Conversions between PE and KE
Examples – roller coaster, ski jumper, skate boarder
Using Energy Conversions
Water stored behind a dam is changed to electrical
energy
Pg 80 for other examples
Law of
Conservation of Energy
States that energy can neither be created
nor destroyed.
It may appear that energy is lost or gained
It
only changed form Example 2nd example
Useful energy is always less than the total amount of
energy
Energy conversions may produce unwanted
forms of energy
Electrical energy may be converted into
unwanted sound energy – (ie) a fan
Energy Transfer Examples
Energy Efficiency
Measurement of usable energy after an
energy conversion
High efficiency
Converts
greater percentage of energy into the
desired form
Low efficiency
Converts
a greater percentage of energy into an
inefficient form