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Energy and Energy Resources

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Energy and Energy Resources Chapter 9 Preview Section 1 What Is Energy? Section 2 Energy Conversions Section 3 Conservation of Energy Section 4 Energy Resources – PowerPoint PPT presentation

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Title: Energy and Energy Resources


1
Energy and Energy Resources
Chapter 9
Preview
Section 1 What Is Energy? Section 2 Energy
Conversions Section 3 Conservation of
Energy Section 4 Energy Resources
Concept Mapping
2
Section 1 What Is Energy?
Chapter 9
Objectives
  • Explain the relationship between energy and
    work.
  • Compare kinetic energy and potential energy.
  • Describe the different forms of energy.

3
Section 1 What Is Energy?
Chapter 9
Energy and Work Working Together
  • Energy is the ability to do work.
  • Work is done when a force causes an object to
    move in the direction of the force. Work is a
    transfer of energy.
  • Energy and work are expressed in units of joules
    (J).

4
Section 1 What Is Energy?
Chapter 9
5
Section 1 What Is Energy?
Chapter 9
Kinetic Energy
  • Kinetic energy is the energy of motion. All
    moving objects have kinetic energy.
  • Kinetic Energy Depends on Mass and Speed If you
    know an objects mass (m) and its speed (v), you
    can calculate the objects kinetic energy with
    the following equation



6
Section 1 What Is Energy?
Chapter 9
Kinetic Energy
Click below to watch the Visual Concept.
Visual Concept
7
Section 1 What Is Energy?
Chapter 9
Potential Energy
  • Potential energy is the energy an object has
    because of its position.
  • Gravitational Potential Energy The amount of
    gravitational potential energy that an object has
    depends on its weight and its height.

8
Section 1 What Is Energy?
Chapter 9
Potential Energy, continued
  • Calculating Gravitational Potential Energy The
    equation to find gravitational potential energy
    is
  • gravitational potential energy ? weight ? height
  • Gravitational potential energy is equal to the
    amount of work done on an object to lift it a
    certain height.

9
Section 1 What Is Energy?
Chapter 9
Potential Energy, continued
  • Height Above What? When you find out an
    objects gravitational potential energy, the
    ground that you measure the objects height
    from depends on where it is.
  • The height you use in calculating gravitational
    potential energy is a measure of how far an
    object has to fall.

10
Section 1 What Is Energy?
Chapter 9
Mechanical Energy
  • Mechanical energy is the total energy of motion
    and position of an object. Both kinetic energy
    and potential energy are kinds of mechanical
    energy.
  • The equation to find mechanical energy is
  • mechanical energy ? potential energy ? kinetic
    energy

11
Section 1 What Is Energy?
Chapter 9
Mechanical Energy, continued
  • The mechanical energy of an object remains the
    same unless it transfers some energy to another
    object.
  • But even if the mechanical energy of an object
    stays the same, the potential energy or kinetic
    energy can increase or decrease.

12
Section 1 What Is Energy?
Chapter 9
Other Forms of Energy
  • Thermal Energy is all of the kinetic energy due
    to random motion of the particles that make up an
    object.
  • All matter is made up of particles that are
    always in random motion. So, all matter has
    thermal energy.
  • Thermal energy increases as temperature
    increases and increases as the number of
    particles increases.

13
Section 1 What Is Energy?
Chapter 9
14
Section 1 What Is Energy?
Chapter 9
Other Forms of Energy, continued
  • Chemical Energy is the energy of a chemical
    compound that changes as its atoms are
    rearranged.
  • Chemical energy is a form of potential energy
    because it depends on the position and
    arrangement of the atoms in a compound.
  • The energy in food is chemical energy.

15
Section 1 What Is Energy?
Chapter 9
Other Forms of Energy, continued
  • Electrical Energy is the energy of moving
    electrons. Electrical energy can be thought of as
    potential energy that is used when you plug in an
    electrical appliance and use it.
  • Sound Energy is caused by an objects
    vibrations. The objects vibrations transmit some
    kinetic energy to the air particles, which also
    vibrate. These vibrations transmit sound energy.

16
Section 1 What Is Energy?
Chapter 9
Other Forms of Energy, continued
  • Light Energy is produced by the vibrations of
    electrically charged particles.
  • Nuclear Energy is energy that comes from changes
    in the nucleus of an atom. Nuclear energy can be
    produced when nuclei are joined in a fusion
    reaction or when a nucleus is split apart in a
    fission reaction.

17
Section 2 Energy Conversions
Chapter 9
Objectives
  • Describe an energy conversion.
  • Give examples of energy conversions for the
    different forms of energy.
  • Explain how energy conversions make energy
    useful.
  • Explain the role of machines in energy
    conversions.

18
Section 2 Energy Conversions
Chapter 9
Kinetic Energy and Potential Energy
  • An energy conversion is a change from one form
    of energy to another. Any form of energy can
    change into any other form of energy.
  • As the skateboarder on the next slide travels up
    and down the half-pipe, his energy changes back
    and forth between kinetic energy and potential
    energy.

19
Section 2 Energy Conversions
Chapter 9
20
Section 2 Energy Conversions
Chapter 9
Kinetic Energy and Potential Energy, continued
  • Elastic Potential Energy Stretching a rubber
    band stores elastic potential energy in the
    rubber band.
  • When you let the rubber band go, it goes back to
    its original shape. It releases its stored-up
    potential energy as it does so.

21
Section 2 Energy Conversions
Chapter 9
Conversions Involving Chemical Energy
  • Chemical energy is stored in the food you eat.
    Your body uses this chemical energy to function.
  • Energy Conversion in Plants The chemical energy
    in the food you eat comes from the suns energy.
    Plants use photosynthesis to convert light energy
    into chemical energy, as shown on the next slide.

22
Section 2 Energy Conversions
Chapter 9
23
Section 2 Energy Conversions
Chapter 9
Conversions Involving Chemical Energy, continued
  • The Process Continues Plants change light
    energy into chemical energy. The chemical energy
    in the food you eat is changed into another kind
    of chemical energy that your body can use.
  • Your body then uses that energy to give you
    kinetic energy that you use in everything you do.

24
Section 2 Energy Conversions
Chapter 9
Why Energy Conversions Are Important
  • Energy conversions are needed for everything we
    do. Heating our homes, getting energy from a
    meal, and many other things use energy
    conversions.
  • Machines, such as a hair dryer, help harness
    energy and make that energy work for you.

25
Section 2 Energy Conversions
Chapter 9
Why Energy Conversions Are Important, continued
  • Conversions Involving Electrical Energy Some
    common energy conversions that involve electrical
    energy are shown in the table below.

Alarm clock electrical energy ? light and sound energy
Battery chemical energy ? electrical energy
Light bulb electrical energy ? light and thermal energy
Blender electrical energy ? kinetic and sound energy
26
Section 2 Energy Conversions
Chapter 9
Energy and Machines
  • A machine can make work easier by changing the
    size or direction (or both) of the force needed
    to do the work. Some machines allow you to use
    less force over a greater distance to do the same
    amount of work.
  • Machines as Energy Converters Some machines
    help you use energy by converting it into the
    form of energy that you need.

27
Section 2 Energy Conversions
Chapter 9
28
Section 3 Conservation of Energy
Chapter 9
Objectives
  • Explain how energy is conserved within a closed
    system.
  • Explain the law of conservation of energy.
  • Give examples of how thermal energy is always a
    result of energy conversion.
  • Explain why perpetual motion is impossible.

29
Section 3 Conservation of Energy
Chapter 9
Where Does the Energy Go?
  • Friction is a force that oppose motion between
    two surfaces that are touching.
  • For a roller coaster car to move, energy must be
    used to overcome the friction between the cars
    wheels and the track.
  • As a result, not all of the cars potential
    energy changes into kinetic energy and not all of
    the cars kinetic energy changes back into
    potential energy.

30
Section 3 Conservation of Energy
Chapter 9
31
Section 3 Conservation of Energy
Chapter 9
Energy Is Conserved Within a Closed System
  • A closed system is a group of objects that
    transfer energy only to each other.
  • The Law of Conservation of Energy states that
    energy cannot be created or destroyed.
  • Energy can be converted from one form to
    another. But all of the different forms of energy
    in a system always add up to the same total
    amount of energy.

32
Section 3 Conservation of Energy
Chapter 9
Energy Is Conserved Within a Closed System,
continued
  • The image below shows energy conservation in a
    light bulb.

33
Section 3 Conservation of Energy
Chapter 9
No Conversion Without Thermal Energy
  • Any time one form of energy is converted into
    another form, some of the original energy always
    gets converted into thermal energy.
  • The thermal energy due to friction that results
    from energy conversions is not usually useful
    energy.

34
Section 3 Conservation of Energy
Chapter 9
No Conversion Without Thermal Energy, continued
  • Perpetual Motion? No Way! A perpetual motion
    machine is a machine that would run forever
    without any additional energy.
  • But perpetual motion machines are impossible
    because some waste thermal energy always results
    from energy conversions.

35
Section 3 Conservation of Energy
Chapter 9
No Conversion Without Thermal Energy, continued
  • Making Conversions Efficient Some systems
    transform energy with less loss of heat than
    others do. Such systems are more efficient than
    others are.
  • Improving the efficiency of machines is
    important because greater efficiency results in
    less waste. If less energy is wasted, less energy
    is needed to operate a machine.

36
Section 4 Energy Resources
Chapter 9
Objectives
  • Name several energy resources.
  • Explain how the sun is the source of most energy
    on Earth.
  • Evaluate the advantages and disadvantages of
    using various energy resources.

37
Section 4 Energy Resources
Chapter 9
Nonrenewable Resources
  • Nonrenewable resources cannot be replaced or are
    replaced much more slowly than they are used.
  • Fossil fuels are nonrenewable energy resources
    that formed from the remains of organisms that
    lived long ago. Oil, natural gas, and coal are
    the most common fossil fuels.

38
Section 4 Energy Resources
Chapter 9
39
Section 4 Energy Resources
Chapter 9
Nonrenewable Resources, continued
  • Uses of Fossil Fuels All fossil fuels contain
    stored energy from the sun, which can be
    converted into other kinds of energy.
  • Burning coal is a common way to generate
    electrical energy. Petroleum is used to make
    gasoline, wax, and plastics. Natural gas is often
    used in home heating.

40
Section 4 Energy Resources
Chapter 9
Nonrenewable Resources, continued
  • Electrical Energy from Fossil Fuels Electric
    generators convert the chemical energy in fossil
    fuels into electrical energy by the process shown
    below.

41
Section 4 Energy Resources
Chapter 9
Nonrenewable Resources, continued
  • Nuclear Energy Another way to generate
    electrical energy is to use nuclear energy.
  • In a process called nuclear fission, the nucleus
    of a radioactive atom is split into two smaller
    nuclei, which releases nuclear energy.
  • Because the supply of radioactive elements is
    limited, nuclear energy is a nonrenewable
    resource.

42
Section 4 Energy Resources
Chapter 9
Renewable Resources
  • Renewable resources are naturally replaced more
    quickly than they are used.
  • Solar Energy Sunlight can be changed into
    electrical energy through solar cells.
  • Solar cells can be used in devices such as
    calculators. They can also be placed on the roof
    of a house to provide electrical energy.

43
Section 4 Energy Resources
Chapter 9
Renewable Resources, continued
  • Energy from Water The potential energy of water
    in a reservoir can be changed into kinetic energy
    as the water flows through a dam.
  • In a hydroelectric dam, falling water turns
    turbines. The turbines are connected to a
    generator that changes kinetic energy into
    electrical energy.

44
Section 4 Energy Resources
Chapter 9
Renewable Resources, continued
  • Wind Energy The kinetic energy of wind can turn
    the blades of a windmill or a wind turbine.
  • A wind turbine changes the kinetic energy of the
    air into electrical energy by turning a generator.

45
Section 4 Energy Resources
Chapter 9
Renewable Resources, continued
  • Geothermal Energy is thermal energy caused by
    the heating of Earths crust. This energy can be
    converted into electrical energy at geothermal
    power plants.
  • Biomass is organic matter, such as plants, wood,
    and waste, that can be burned to release energy.
    Some countries depend on biomass for energy.

46
Section 4 Energy Resources
Chapter 9
The Two Sides to Energy Resources
  • All energy resources have advantages and
    disadvantages. Many factors determine when one
    energy source is a better choice than another.
  • Choosing the Right Energy Source Energy
    planning in all parts of the world requires
    careful consideration of energy needs and the
    availability and responsible use of resources.
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