Energy

Chapter 3

Energy Exists in Different Forms

• Energy has many different forms • Almost everything around you requires energy • Think of one process that requires energy. _______________________________________

Energy

• Energy is the ability to cause change. • All forms of energy have one point in

common: They cause changes to occur – The flow of electrical energy through a

wire causes a cool, dark light bulb to get hot and glow.

Forms of Energy

• Mechanical • Sound • Chemical • Thermal • Electromagnetic • Nuclear

Mechanical Energy

• The energy that moves objects is mechanical energy – Example: The energy you use to brush your teeth

Sound Energy • Sound results from the

vibration of particles in a solid, liquid or gas

• People and other animals can detect these tiny vibrations with structures in their ear.

• http://www.noiseaddicts.com/2009/03/can-you-hear-this-hearing-test/

Chemical Energy• Energy that is stored in the chemical

composition of matter is chemical energy. • When wood or gasoline burns, chemical

energy produces heat.

Thermal Energy• The total amount of energy from the

movement of particles in matter is thermal energy.

• The atoms and molecules in matter are always moving.

• The energy of this motion in an object is thermal energy.

Electromagnetic Energy

• Electromagnetic energy is transmitted through space in the form of electromagnetic waves.

• Unlike sound, electromagnetic waves can travel through empty space.

• These waves include: visible light, x-rays, and microwaves.

Electromagnetic Energy

• X-rays are high energy waves used by doctors and dentists to look at your bones and teeth.

Electromagnetic Energy

• Microwaves can be used to cook food or or transmit cell phone calls.

Electromagnetic Energy

• The sun releases a large amount of electromagnetic energy, some of which is absorbed by Earth.

Nuclear Energy• The center of an atom – its nucleus – is a

source for nuclear energy.

Nuclear Energy

• A large amount of energy in the nucleus holds the nuclear particles together.

• When a heavy atom’s nucleus breaks apart, or when the nuclei of two small atoms join together, energy is released.

• Nuclear energy released from fusing of small nuclei to form larger nuclei keeps the sun burning.

Kinetic Energy and Potential Energy

• All forms of energy can be described in terms of two general types of energy: Kinetic and potential.

Kinetic Energy

• The energy of motion is called kinetic energy.– It depends on both the object’s mass and the speed of the

object’s movement. • Kinetic Energy increases as mass increases – If a bowling ball and soccer ball were moving at the same

speed, the bowling ball would have more kinetic energy because of its larger mass.

• Kinetic energy increases as speed increases. – If two identical bowling balls were rolling along at different

speeds, the faster one would have more kinetic energy because of its greater speed.

Potential Energy

• Potential Energy is the stored energy that an object has due to its position or chemical composition.

Potential Energy• The most obvious form of potential energy

is potential energy that results from gravity. Gravity is the force that pulls objects towards Earth’s surface.

• Another form of potential energy comes from stretching or compression an object.

Think-Pair-Share

• How can you tell kinetic energy and potential energy apart?

Energy Changes Forms But is Never Lost

• Potential Energy can be changed into kinetic energy and back into potential energy

Think-Pair-Share

• Come up with a scenario where kinetic energy changes to potential energy and back to the kinetic energy.

Energy is Always Conserved

• The law of conservation states that energy can neither be created nor destroyed.

• When you observe energy in your daily life, it may seen that the energy constantly disappears, but it is just changing forms.

Law of Conservation

• Conservation of energy is a balance of energy in the universe.

• When a soccer ball is kicked, a certain amount of energy is transferred by the kick.

• The ball gains an equal amount of energy, mostly in the form of kinetic energy.

• The ball’s kinetic energy decreases as some of that energy is converted into sound energy and heat from the friction between the ball and the ground.

Energy Conversions May Produce Unwanted Forms of Energy

• When energy changes forms, the total amount of energy is conserved; however, the amount of useful energy is usually less than the total amount of energy.

• Example of the fan.

Energy Conversions May Produce Unwanted Forms of Energy

• Energy efficiency is a measurement of usable energy after an energy conversion.

• You may be familiar with energy-efficient house-hold appliances.

• Less energy is need to operate appliances that are energy efficient.

Technology Improves Energy conversion

• In many common energy conversions, most of the wasted energy is released as heat.

• One example is the common incandescent light bulb. Only about 5% of the electrical energy is converted to light. That means 95% of energy is turned into unwanted forms of energy.

Technology Improves Efficiency• To decrease this amount of wasted energy, scientists

have investigated several more efficient types of lights.

• Example: LED Light Bulb: Convert almost all energy into light. They were dull originally but scientists have made major improvements. They are used in TVs, remotes, computers, outdoor signs, traffic lights and many other objects.

Efficient Cars

Technology Improves the Use of Energy Resources

• Much of the energy used on Earth comes from fossil fuels such as coal, petroleum, and natural gas; however, the supply of fossil fuels are limited.

• Scientists are exploring alternative methods of energy: solar, wind, and water power.

Solar Energy• Solar cells are important in today’s solar

energy technology.• Solar cells are made of several layers of light-

sensitive material, which convert sunlight directly into electrical energy.

Wind Energy• For many centuries, people have used kinetic

energy of wind to sail ships. • Recently, windmills have been used to

generate electrical energy.

Water Energy• The kinetic energy of water can be converted to

electrical energy. • On the Canadian side, the power plants at Niagara

Falls have the capacity to produce ~ 4.9 million kilowatts. That's enough to power 3.8 millions homes.