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
Concept Mapping
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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.

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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).

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Section 1 What Is Energy?
Chapter 9
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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

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Section 1 What Is Energy?
Chapter 9
Kinetic Energy
Click below to watch the Visual Concept.
Visual Concept
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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.

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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.

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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.

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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

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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.

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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.

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Section 1 What Is Energy?
Chapter 9
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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.

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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.

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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.

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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.

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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.

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Section 2 Energy Conversions
Chapter 9
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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.

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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.

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Section 2 Energy Conversions
Chapter 9
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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.

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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.

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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
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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.

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Section 2 Energy Conversions
Chapter 9
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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.

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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.

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Section 3 Conservation of Energy
Chapter 9
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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.

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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.

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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.

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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.

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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.

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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.

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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.

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Section 4 Energy Resources
Chapter 9
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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.