Chapter 16: Energy Forms and Conversions
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Chapter 16:
Energy Forms and Conversions
state what is meant by energy
describe different forms of energy and how energy changes from one form to another
infer that energy is conserved and can be transformed from one form to another
appreciate the need for Singapore – which has no natural resources of her own – to conserve energy
Lesson Outline
Different forms of energy
Energy types
electrical
light
heat
kineticpotential
nuclear
sound
There are different forms of energy:
16.1 Energy and Its Various Forms
Energy is the ability to do work.
You make use of different types of energy to help you do work in your daily life.
chemical
state what is meant by energy
describe different forms of energy and how energy changes from one form to another
infer that energy is conserved and can be transformed from one form to another
appreciate the need for Singapore – which has no natural resources of her own – to conserve energy
Lesson Outline
Potential energy is a form of stored energy.
Potential energy
1 Gravitational potential energy
2 Chemical potential energy
3 Elastic potential energy
(a) Potential Energy
Elastic potential energy
Gravitationalpotential energy
Chemical potential energy
Gravitational Potential energy
Gravitational force• The earth is kept in it’s orbit by the sun’s
gravitational pull
SunEarth
(1) Gravitational potential energy•The airplane's stored energy is due to its elevated position in a region where there is gravity. This type of potential energy is called gravitational potential energy.
Gravitational Potential Energy
• If two objects have the same mass but are at different heights, the one with the greater height will have more gravitational potential energy.
Gravitational Potential Energy
• If two objects are at the same height from the ground, the one with the greater mass will have more gravitational potential energy.
The formula for Gravitational Potential
Energy•G.P.E = Mass x Gravity x Height
•G.P.E = mgh
•This is found in stretched or compressed elastic objects (e.g., compressed spring)
Which equipment make use of a spring to work?
(2) Elastic potential energy
Elastic Potential Energy• Elastic potential
energy is the energy stored in an elastic object when it is pushed or pulled.
• When an elastic object is pushed or pulled, it stores energy which can be released to do work.
•The stored energy in the food is called chemical potential energy.•Chemical energy is the energy which holds the atoms and molecules of substances together.
This stored energy is released during chemical reactions. What is the name of
chemical reaction/s that release energy in
1. the body?
2. the fuels?
(3) Chemical potential energy
Chemical Potential Energy
It is found in fuels, food, batteries and in living things. It is only released
when a chemical reaction takes place.
Summary of Potential Energy
• Potential energy is stored energy in a body as a result of its position or condition
• 3 types of potential energy– Gravitational– Elastic– Chemical
Kinetic Energy
Kinetic Energy is the energy of a body due to its motion.
(b) Kinetic energy
•The amount of the energy is directly proportional to the mass of an object.
Why cars and bullets can cause damage at high speeds?
Kinetic energy
• Kinetic energy is the energy that a body possesses due to its motion.
Moving objects possess kinetic energyMoving objects possess kinetic energy
Kinetic Energy
• If two objects have the same mass but are moving at different speeds, the one with the greater speed will have more kinetic energy.
Kinetic Energy
• The greater the mass of a moving object, the greater its kinetic energy.
Formula for Kinetic Energy
•K.E = (1/2)(mass)(velocity)2
•K.E = (1/2)mv2
Light Energy
(c) Light energy
•Light is a form of energy that allows us to see things and for plants to make food.
•Optical fibres also make use of light to transmit huge amounts of information over long distances at high speeds.
An optical fibre is a glass or plastic fibre designed to guide light along its length. Did You Know??
What is this chemical process?
Light Energy
• Light is a form of energy which enables us to see.
• A light source produces its own light.
• The Sun is our main source of light.
Sound Energy
• Sound is a form of energy produced by vibrations which can be detected by our ears.
• A loud sound carries more energy than a soft sound.
Your voice is produced when the vocal cords in your voice box vibrates. Unlike the vibrations of a string, the vibrations of some objects are not so easily observed.
Sound Energy
• Sound can travel through
solid liquid gas
• But cannot travel through vacuum.
Sound energy
• Loud sounds and noise cause sound pollution.
• Sounds produced by musical instruments are pleasant to our ears.
Electrical Energy
• Electrical energy is a form of energy made available by the flow of electric charges such as electrons and ions.
• Electric cells and power points are the main sources of electrical energy.
• The electrical energy from power points comes from power stations.
Electrical Energy
•It is widely used as it can be easily generated and transmitted over long distances and be converted into other forms of energy to do work.
•Can you name examples in the classroom?
Heat Energy
Heat Energy• It is a form of energy comes from the internal
motion of the particles in a body;• Heat is a form of energy which flows from a region
of higher temperature to a region of lower temperature.
• The Sun is our main source of heat.– This shows that heat can travel through
VACUUM.
• It can travel through solids, liquids, gases and vacuum.
• We can obtain a large amount of heat from burning fuels.
Nuclear Energy
(g) Nuclear energy
• It is a form of energy that comes from a nuclear reaction. Two types of nuclear reaction:
- Nuclear fusion: Large amount of energy is released when nuclei of small atoms combine to form heavier ones.
(e.g., energy of the Sun)
- Nuclear fission: Energy is produced when the nucleus of a heavy atom is split into smaller ones. (e.g., nuclear power stations)
• It can be disastrous if it is abused.
(e.g., nuclear bombs used in World War II)
• Sun energy is produced when small atoms combine to form heavier ones.
• Nuclear energy from power stations is produced when a heavy atom is split into smaller ones.
• Nuclear energy can be disastrous is abused or released without proper control.
Chernobyl Disaster
A nuclear accident at a nuclear power plant in
Chernobyl, Ukraine, in 1986 killed thousands of people. Many of them suffered from cancers caused by exposure
to the harmful radiation released.
Clarification• Work is the transfer of energy.
• Calculation of Energy
SI unit of Energy : Joule (J)
K.E. = ½ mv2
where m is the mass and v is the velocity of the object
Gravitational P.E. = mgh
where m is the mass, g is gravitational force and h is the height of the object
A man of mass 80 kg is moving at a speed of 2.0 m/s. Calculate the kinetic energy of the man.
Clarification• KE = ½ mv2
= ½ x 80 x 2.02
= 160 J
Gravitational P.E. = mgh
where m is the mass, g is gravitational force and h is the height of the object
An apple of mass 0.10 kg at the height of 2.0 m on a tree. Calculate the P.E. of the apple.
Definition of energy: ________________________________________________________________________________________________
The seven forms of energy are __________________________________________________________________________
• Objects which have a greater____________ or are at a greater___________ possess more kinetic energy.
• Objects which have a greater ____________ or are at a greater ____________ possess more gravitational potential energy.
• The two sources of electrical energy are the _____________ and _____________.
Definition of energy:
The ability to do work.
The seven forms of energy are:
Potential, Kinetic, Light, Sound, Heat, Electrical, Nuclear
• Objects which have a greater___mass___ or are at a greater__speed__ possess more kinetic energy.
• Objects which have a greater ___mass___ or are at a greater __height___ possess more gravitational potential energy.
• The two sources of electrical energy are the __battery/electric cells___ and ___powerpoint___.
electrical energy
car being pulled up by electrical winch
mechanical energy (potential energy + kinetic energy)
gravitational potential energy
Electrical energy Gravitational potential energy Mechanical energy + Heat energy
state what is meant by energy
describe different forms of energy and how energy changes from one form to another
infer that energy is conserved and can be transformed from one form to another
appreciate the need for Singapore – which has no natural resources of her own – to conserve energy
Lesson Outline
• The energy is converted from one form to another when work is done.
For e.g.,
Solar panels capture light energy from the Sun, and convert it to electricity.
Green plants undergo photosynthesis to convert light energy into chemical energy in the form of food.
16.2 Conversion of Energy
Conversion of Energy
• Potential energy of the book at a greater height change to kinetic energy as the book falls.
• PE decreases while KE increases.
Conversion of Energy
• Chemical Energy stored in the body is converted to kinetic energy as the body is moving.
• Kinetic Energy is then converted to Potential Energy as the body gains height.
Conversion of Energy
• The car engine allows the stored chemical energy of gasoline to be transformed into mechanical energy that drives the wheels of the car.
Conversion of Energy
• Electrical Energy convert to light and thermal energy as the electrical light bulb lights up.
Conversion of Energy
• Light Energy from the sun converted to Electrical Energy in a solar panel.
Conversion of Energy
• Wind mills make use of the kinetic energy of the air molecules, transforming it to mechanical or electrical energy.
Conversion of Energy
• Hydroelectric plants transform the kinetic energy of falling water into electrical energy.
Rubbing your hands together
Kinetic Energy Sound Energy + Heat Energy
Shaking a bottle of beansKinetic Energy Sound Energy
Burning Wood
Chemical Potential Energy
Heat Energy + Light Energy
Singing into a microphone
Sound Energy
Electrical Energy
Plants Photosynthesizing
Light Energy Chemical Potential Energy
Kinetic Energy Elastic Potential Energy Gravitational Potential Energy Kinetic Energy
Pole Vaulting
Pendulum Bob
X
Y
Z
Highest potential energy
Highest potential energy
Highest kinetic energy
Lowest kinetic energy
Lowest kinetic energy
Lowest potential energy
Energy is conservedThe conservation of energy states that
(i)energy cannot be created or destroyed but
(ii)energy can change from one form into another.
Potential energy Kinetic energy TOTAL TOTAL=
WASTED ENERGY
USEFUL ENERGY(USED TO DO WORK)
+ Heat energy + Sound energy
Energy cannot be created nor destroyed. It can be converted from one form into another, and each time, work is always done.
• In any closed system, the total amount of energy remains constant before and after work is done, regardless of any process taking place.
• When more work is done, more energy is converted.
Laws of Conservation of Energy
By the Law of conservation of energy• Total energy at A =Total energy at B=Total
energy at C
• ( PEA ) = ( PEB + KEB ) = ( KEC )
• mg(x+n) = mgn + 1/2 mvB2 = 1/2 mvmax
2
x
n
A
B
C
PEA (at rest)KE=0
PEB
KEB
KECPE=0
The law of conservation of energy states that
(i)___________________________________
(ii)___________________________________
Energy conversion for a toaster:
________________
________________
________________
Light energy is converted to chemical potential energy in a ________________.
Chemical potential energy is converted to electrical energy in a ________________.
We cannot hear sound in a _______________.
The law of conservation of energy states that
(i)energy cannot be created or destroyed but
(ii)energy can change from one form into another.
Energy conversion for a toaster:
Electrical energy Heat and Light energy
Light energy is converted to chemical potential energy in a plant.
Chemical potential energy is converted to electrical energy in a power station.
We cannot hear sound in a vacuum.
How is electrical energy produced?• A power station uses fossil
fuels such as coal, natural gas and oil.
• When these fossil fuels are burnt, the chemical energy stored in these fuels is released to boil water to form steam.
• The moving steam turns the turbines which turns the generator.
• When the generator turns, electrical energy is produced.
The energy conversions in the power station :
chemical energy heat energy kinetic energy electrical energy
The energy conversions in the power station :
chemical energy heat energy kinetic energy electrical energy
Oil drilling rig
Non Renewable Sources of Energy
Coal mine
These fossil fuels pollute the environment when they are burnt.
They are limited, i.e. they will run out.
These alternative sources of energy are clean (pollution free) and do not run out.
However, they are expensive or unsuitable to harness in some places.
Wind energyA wind turbine uses energy from
wind to turn the turbines.A wind turbine uses energy from
wind to turn the turbines.Need a large area of landNeed a large area of land
Solar panelsA solar panel uses heat from the sun.A solar panel uses heat from the sun.Expensive and need hot climateExpensive and need hot climate
Solar cells
Geothermal Power
A geothermal power plant uses heat from the earth.
A geothermal power plant uses heat from the earth.
Expensive to installExpensive to install
Biomass Energy
• Fuels such as biogas and alcohol are derived from biomass (plant materials or wastes from living things)Take up valuable fertile land.
Need the correct climateTake up valuable fertile land.
Need the correct climate
Hydroelectricity Power
A hydroelectric power station uses energy from falling water.A hydroelectric power station uses energy from falling water.
Requires mountainous areasRequires mountainous areas
Wave energyInterfere with shipping
ExpensiveInterfere with shipping
Expensive
Tidal energyFew places are suitableExpensive
Few places are suitableExpensive
The Future
• Science tells us we must turn towards energy sources that are:
- renewable;
- sustainable;
- less polluting.
We need to learn how to use energy more
efficiently and responsibly.
Conserving Energy
We’ve only run 1 km of the
marathon. I’m conserving energy for the rest of the
race!
Hey! Why are you running so slowly?
Conserving Energy
• Singapore has no natural resources, it has to depend on IMPORTED fossil fuels to meet its energy needs.
• Hence, it is very important for us to conserve energy by:– Developing and using energy efficient devices. (use
fluorescent lamps instead of filament lamps)– Recycling and reusing materials– Use public transport system– Switch off electrical appliances when not using them
Saving Energy
• Developing and using energy-efficient devices and processes
• Reducing wastage of energy
• Recycling and reusing materials
• Using more efficient public transportation systems
• Saving and optimising the use of electricityInverter air-con
• Fossil fuels is a form of _________________ source of energy.
• The two disadvantages of using fossil fuels as a form of energy are that ________________
_____________________________________.
Examples of fossil fuels are _________________________.The form of energy stored in fossil fuels is ________________ energy.
The seven types of renewable sources of energy are ______________________________________________________________________________
The energy conversion in power stations (fossil fuels): ___________________________
• Fossil fuels is a form of non-renewable source of energy.
• The two disadvantages of using fossil fuels as a form of energy are that they pollute the environment and they are limited/will run out.
Examples of fossil fuels are coal, oil and natural gas. The form of energy stored in fossil fuels is chemical potential energy.
The seven types of renewable sources of energy are wind, tidal, waves, hydroelectricity, biomass, geothermal and solar.
The energy conversion in power stations (fossil fuels): chemical energy heat energy kinetic energy electrical energy.
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