Chapter 12: Energy and Energy Chapter 12: Energy and Energy ResourcesResources

Carin MirandaCarin Miranda

6-16-1

20072007

What is Energy?What is Energy?

• Energy is the ability to Energy is the ability to do work.do work.• Work and energy are Work and energy are both expressed in joules both expressed in joules (J).(J).

Kinetic EnergyKinetic Energy

• Kinetic energyKinetic energy is the energy of motion. is the energy of motion.• All moving objects have kinetic energy.All moving objects have kinetic energy.• Kinetic energy= mass times speed Kinetic energy= mass times speed

squared divided by 2.squared divided by 2.• The faster something is moving, the The faster something is moving, the

more kinetic energy it has.more kinetic energy it has.• The more massive the object the more The more massive the object the more

kinetic energy it has.kinetic energy it has.

Potential EnergyPotential Energy

• Potential energyPotential energy is energy based on is energy based on shape or position.shape or position.

• Gravitational potential energy is based Gravitational potential energy is based on height and weight.on height and weight.

• The higher an object the more potential The higher an object the more potential energy.energy.

• The more massive an object the greater The more massive an object the greater the potential energy.the potential energy.

Mechanical EnergyMechanical Energy

• Mechanical energy is the total Mechanical energy is the total energy of motion and position. energy of motion and position.

• In other words it is kinetic plus In other words it is kinetic plus potential.potential.

• As potential goes up kinetic As potential goes up kinetic goes down and vice versa.goes down and vice versa.

Forms of energyForms of energy

• Thermal (Heat)Thermal (Heat)• ChemicalChemical• ElectricalElectrical• SoundSound• LightLight• NuclearNuclear

ThermalThermal• Higher temperature objects have more Higher temperature objects have more

thermal energy and more kinetic energy.thermal energy and more kinetic energy.• The particles in steam move faster than The particles in steam move faster than

the particles in ice.the particles in ice.• The more particles the more thermal The more particles the more thermal

energy.energy.• A bathtub full of 75 degree water would A bathtub full of 75 degree water would

have more thermal energy than a cup have more thermal energy than a cup full of 75 degree water.full of 75 degree water.

Chemical EnergyChemical Energy

• When particles are broken When particles are broken down and cannot return to down and cannot return to their original form they have their original form they have chemical energy.chemical energy.

• Examples: Food, Charcoal, Examples: Food, Charcoal, gasoline, firewood.gasoline, firewood.

Electrical EnergyElectrical Energy

• Moving electrons.Moving electrons.• Any electrical appliances or Any electrical appliances or

anything using electricity.anything using electricity.• Huge magnets are rotated to Huge magnets are rotated to

produce the electricity you produce the electricity you use at home.use at home.

Sound EnergySound Energy

• Caused by an objects Caused by an objects vibrations.vibrations.• It is a form of potential It is a form of potential and kinetic energy.and kinetic energy.

Light EnergyLight Energy

• Vibrations of electrically Vibrations of electrically charged particles.charged particles.

• Not all light energy is seen.Not all light energy is seen.• Microwaves use light Microwaves use light

energy.energy.

Nuclear EnergyNuclear Energy

• Two or more nuclei join together Two or more nuclei join together (nuclear fusion). Example: Sun(nuclear fusion). Example: Sun

• Nucleus of an atom splits apart Nucleus of an atom splits apart (nuclear fission). Example: (nuclear fission). Example: Uranium atoms split apart to Uranium atoms split apart to produce electricity.produce electricity.

Energy ConversionsEnergy Conversions

• Any change from one Any change from one form of energy to form of energy to another.another.

Kinetic to PotentialKinetic to Potential

• Remember we said as potential Remember we said as potential energy goes up kinetic goes energy goes up kinetic goes down and vice versa.down and vice versa.

• Examples: Person on a Examples: Person on a trampoline, pendulum, and trampoline, pendulum, and wind up toys.wind up toys.

Chemical Energy ConversionsChemical Energy Conversions

• Chemical energy in food is converted into Chemical energy in food is converted into kinetic energy when you move. kinetic energy when you move.

• It is stored as potential energy when you It is stored as potential energy when you aren’t moving. aren’t moving.

• Where did that chemical energy come from in Where did that chemical energy come from in food? food?

• The sun gives plants light energy and they The sun gives plants light energy and they convert it into chemical energy.convert it into chemical energy.

• Batteries are another example of chemical Batteries are another example of chemical energy.energy.

Electrical Energy ConversionsElectrical Energy Conversions

• Lots of examples:Lots of examples:• Alarm clock: electrical to light and Alarm clock: electrical to light and

sound.sound.• Battery: chemical to electricalBattery: chemical to electrical• Light bulb: electrical to light, thermal, Light bulb: electrical to light, thermal,

and sometimes sound.and sometimes sound.• Blender: electrical to kinetic and Blender: electrical to kinetic and

soundsound

Energy and MachinesEnergy and Machines

• Machines make work Machines make work easier by changing the easier by changing the size and/or direction of size and/or direction of the force required to do the force required to do the work.the work.

Why Conversions are ImportantWhy Conversions are Important

•Make energy Make energy useful.useful.•Make conversions Make conversions more efficient.more efficient.

Conservation of EnergyConservation of Energy

• Friction is a force that opposes motion Friction is a force that opposes motion between two surfaces that are touching.between two surfaces that are touching.

• When energy is used to overcome When energy is used to overcome friction some energy is converted into friction some energy is converted into thermal energy.thermal energy.

• On a roller coaster potential energy is On a roller coaster potential energy is greatest at the top of the biggest hill and greatest at the top of the biggest hill and kinetic energy is greatest at the bottom kinetic energy is greatest at the bottom of the biggest hill.of the biggest hill.

Law of Conservation of EnergyLaw of Conservation of Energy

• Energy can be neither created nor Energy can be neither created nor destroyed.destroyed.

• It can change from one form to It can change from one form to another.another.

• Every time an energy conversion Every time an energy conversion takes place some energy is always takes place some energy is always converted into thermal energy.converted into thermal energy.

Energy ResourcesEnergy Resources

• A natural resource that can A natural resource that can be converted by humans into be converted by humans into another form of energy to do another form of energy to do useful work.useful work.

• Can be nonrenewable or Can be nonrenewable or renewable.renewable.

NonrenewableNonrenewable

• Cannot be replaced easily.Cannot be replaced easily.• Fossil Fuels: Formed from the Fossil Fuels: Formed from the

buried remains of plants and buried remains of plants and animals that lived millions of years animals that lived millions of years ago.ago.

• Coal, petroleum, and natural gas.Coal, petroleum, and natural gas.• Electrical energy from fossil fuels.Electrical energy from fossil fuels.• Nuclear Energy (Uranium pellets).Nuclear Energy (Uranium pellets).

RenewableRenewable

• Can be replaced over a relatively short Can be replaced over a relatively short period of time.period of time.

• Solar Energy (SUN).Solar Energy (SUN).• Energy from water (Hydroelectric).Energy from water (Hydroelectric).• Wind Energy.Wind Energy.• Geothermal (Hot water in the ground).Geothermal (Hot water in the ground).• Biomass (garbage).Biomass (garbage).

Advantages and Disadvantages of Advantages and Disadvantages of Nuclear EnergyNuclear Energy

• Advantages: very concentrated Advantages: very concentrated form of energy and nuclear power form of energy and nuclear power plants don’t produce smog (CO2).plants don’t produce smog (CO2).

• Disadvantages: Produces Disadvantages: Produces radioactive waste and it is radioactive waste and it is nonrenewable.nonrenewable.