Transcript Energy Reviewx

Energy
The ability to bring about change or do work.
Energy Transformation:
Change from one type of
energy to another.
Energy Transfer
When a certain form of
energy moves to another
object.
Kinetic Energy: Energy an object has due to its motion.
Potential Energy:
Energy that is stored in an object.
Roller Coaster Showing potential and kinetic energy transformation
A
A
B
D
E
C
Which point(s) will have the maximum potential energy? A
Which point(s) will have the least potential energy? C and then E
Which point(s) will have the maximum kinetic energy? C and then E
Which point(s) will have both kinetic and potential energy?
B and D
Gravitational Potential Energy
mass and _______.
Is a type of potential energy considering the and objects _______
height
• The more mass = More or Less GPE
• The more distance = More or Less GPE
You are
correct I
am lower!
I have more GPE because
we have the same mass ,
but I am at a greater height!
Which skier has
more GPE? Why?
Temperature
Is the measure of the average kinetic energy (energy of motion) or average speed of
all the particles in a material.
• Higher temperature = particles move faster
and farther apart
• Lower temperature = particles move slower
and closer together
Cooler water
particles moving
slower and close
together; take longer
for blue dye to
spread
Which water is hotter?
Hotter water
particles moving
faster and farther
apart; blue dye
spread out quickly
Heat
Is the transfer of energy from a place with higher temperature to a place of
lower temperature.
An object does not “have” heat
Thermal Energy
Thermal energy is the energy a substance or system has related to
its temperature, i.e., the energy of moving or vibrating
molecules. Atoms and molecules, the smallest particles of any
substance, are always in motion. The motion of thermal energy is
usually not visible, but we can feel or see its effects. We use
thermal energy to cook our food and heat our homes, and we use
it to generate electricity.
• Total kinetic energy of all the particles in a material
• More molecules = more thermal energy
• Almost always released (not lost or
destroyed) during an energy
transformation- felt has heat
Can you have the same temperature water
but have different amounts of thermal
energy?
YES
more atoms,
more thermal
energy
less atoms,
less thermal
energy
Law of Conservation of Energy
• Energy can be transferred or transformed but can not be created or destroyed
• The total amount of energy before something happens must be equal to the
amount afterward
• Total energy does not change
True or False: A friend tells you that a generator “makes” electricity.
Energy Efficiency
• No energy transformation results in 100% useful energy
• Ratio of useful energy to that is released to the total energy used
Example: Gas in car
• 74% of energy released as heat
• 26% of energy is transformed into motion
• Engines efficiency= 26%
Energy Types
Since energy is never created or destroyed – follow energy transfer
Transfer of Energy
Using the table on the previous
page, decide the type of energy at
each of the situations.
Transfer of Energy
Conduction When two objects touch each other and transfer energy
from the hotter one to the colder one - gases, solids,
liquids – due to the collision of atoms and molecules.
Conductor
Materials that allow energy to transfer easily.
Insulators
When conduction is slowed down, insulation occurs.
• Less collision of atoms and molecules
• Gases poor conductors (vacuum)
Results
Final temperature 40 0C
Temperature Change
• 60 0C
- 20 0C
• 20 OC
+ 20 OC
Final temperature 48 0C
Temperature Change
• 60 0C
- 12 0C
• 20 OC
+ 28 OC
Final temperature 34
Temperature Change
• 60 0C
- 26 0C
• 20 OC
+ 14 OC
Calculating Energy Lost
Energy unit of measurement
•
•
•
•
Calorie
joule,
BTU
(1 cal = 4.2 joules)
• One calorie is the amount of energy required to raise 1 gram of water 1 C
• 1 mL of water weighs 1 gram
• Food Calories: Calorie (capital C) = 1000 calories
How to Calculate Calories
Energy released (calories) = Temperature change of water (c) X Mass of water (g)
Measuring Calories In Food
Mass of 1 cheese ball
1.2 g
Volume of water
100mL
Initial temperature of water
20 OC
Final temperature of water
36 OC
According to the results, how many calories in a cheese ball? And in a serving?
Calories = Change temp. X Mass water
21 OC x 100g
= 2,100 calories
Convert to food Calories divide by 1,000
= 2.1 Calories per cheese ball
2.1 Calories per cheese ball
32 cheese balls per serving
2.1 X 32
= 67.2 Calories/serving
The nutrition information on the cheese ball bag states 32 cheese balls contain 150
Calories. Propose several reasons why the value you calculated is lower than the energy
actually stored in a cheese ball.
Renewable and Nonrenewable Resources
Nonrenewable Resources
• Limited supply
• once it is used up there is no more of it!
Fossil Fuels
Nuclear Energy
(coal, petroleum, natural gas)
Renewable Resources
• Continuing supply
• supplied faster than it is used up!
Tidal Harness
Biomass Energy
Solar Energy
Hydroelectric Energy
Geothermal Energy
Wind Energy
Energy Sources
Which Energy Sources are
considered renewable?
•
•
•
•
•
•
Biomass
Geothermal
Hydroelectric
Solar
Tidal Harness
Wind Energy
Which Energy Sources are
considered nonrenewable?
• Fossil Fuels (coal, petroleum, natural gas)
• Nuclear Energy
Battery
• Chemical energy to electrical energy to - mechanical, light, etc
(potential)
(kinetic)
• Electrolyte - material capable of conducting electricity that allows
the current to flow as it is released from the reaction.
• Electrons flow from negative to positive
How does a battery work video
http://www.youtube.com/watch?v=CX84l5ZZHVg
How a Battery Works
KEY
Electrons
Flow of electricity
Copper
• Positive terminal
• least active
• gain electrons
_
_
_
_
_
_
_
_
_ Electrolyte
_
_
_ __
__
_
_
_
_
Magnesium
• Negative terminal
• most active
• gives up electrons
According to the charts, which metal
would you pair with Lithium to make
a strong battery? Explain your choice
Lithium should be paired with Gold
to produce the most energy
releasing battery. Lithium is most
active thus making it want to give
up electrons. Gold is least active
thus making it want to gain
electrons. This movement of
electrons makes electricity.
Negative terminal
give up electrons
Positive terminal
gain electrons
Energy and Magnetic Fields
Earth is a gigantic magnet
Earth’s geographic north
pole is Earth’s magnetic
south pole.
Electromagnetism Video
http://www.youtube.com/watch?v=HQdLFEiVeCA
http://www.youtube.com/watch?v=cy6kba3A8vY
Electrical Circuits
Predict if the following materials conduct electricity!
Material
Conducts
Electricity
Aluminum
yes
Copper
yes
Glass rod
no
Carbon rod
yes
Wood
no
Zinc
yes
Granite
yes
Plastic
no
Ceramic tile
no
Magnesium
yes
Iron
yes
Parallel and Series Circuit
Does the diagram represent a parallel or series circuit?
What happens if you unscrew one of the light bulbs?
All the lights will go out since there will be a break in the circuit. The
flow of electricity will stop and not be able to complete the circuit.
Does the diagram represent a parallel or series circuit?
What happens if you unscrew one of the
light bulbs?
All the lights will stay on since there will
not be a break in the circuit. The flow of
electricity will continue and complete the
circuit.
Lightbulb Efficiency
Are lightbulbs better at producing light or heat?
Which is the best lightbulb? Use evidence from the chart.