Transcript Energy Transformations

Energy Transformations
The law of conservation of energy states that
energy is not created nor destroyed, however
energy can change from one form to another.
There are 3 main forms of energy:
•Kinetic (motion of particles),
•Potential (based on position of particles),
•Radiant (doesn’t require particles)
Energy Transformations
For example, your car uses gasoline to cause
the car to move. Within the bonds of the
gasoline molecules is stored energy
(potential). The molecules undergo a
chemical reaction (also potential) to generate
heat (kinetic) which, through a series of
simple machines, causes the car to move
(kinetic). If you happened to use a solar
powered car (rather than gasoline), then you
would be using radiant energy to cause the
car to move (kinetic).
Energy Transformations
Kinetic: movement of particles
•Mechanical: movement of macroscopic
particles EX: spinning wheels, moving your
finger
•Thermal: movement of microscopic particles
(such as atoms, molecules) EX: heat,
movement of helium gas atoms
–Kinetic thermal energy can be transferred
from one particle to another via conduction
and convection (there is a 3rd, but we are
skipping it for now) see the next slide
Energy Transformations
Kinetic Thermal Energy
Conduction: When particles collide with one
another, energy is transferred from the faster
(more energy) moving particle to the slower
(less energy) moving particle. This makes the
slower moving particle increase in speed.
–In solids, particularly metals, electrons are able
to move from atom to atom. Electron flow will
increase in speed with addition of thermal energy,
increasing the conductivity of a substance.
–Rate of transfer of thermal energy depends upon
the separation of the particles and their freedom
to move. Which phase do you think best
conducts thermal energy?
Energy Transformations
Kinetic Thermal Energy
Convection: Involves the transfer of thermal
energy by the motion of a fluid (a fluid is a
liquid or a gas), or by currents.
–As the fluid is heated from below, the particles at
the bottom move faster, causing them to reduce
in density (they spread apart)
–The less dense particles rise to the top, as the
denser, cooler (less thermal energy) fluid moves
to the bottom, creating a current
–The convection current will keep stirring this
way. The warmer fluid will always move away
from the
Energy Transformations
Potential: based on position of particles
(any size)
•Electrostatic: due to a difference in charge
EX: chemical bonds (chemical reactions) electricity,
+ ion attracted to a – ion to form an ionic compound
•Elastic: due to deformation of an elastic object
EX: stretched spring, stretched rubber band
•Gravitational: due to attraction to an object with a
large mass
EX: moon attracted to earth, book falling off desk
toward earth
Energy Transformations
Radiant: energy does not require particles
since it travels through electric fields
•Electromagnetic: light
EX: sunlight, light from light bulbs
•Nuclear: reactions which occur within
nucleus of an atom
EX: sun (stars) creating other elements from
hydrogen, atomic bomb, radioactivity, fusion,
fission