Forms and Uses of

Energy

16.1 What is Energy?

• Energy is the ability to do work.

• Living things need energy for the processes that keep them alive.

• Non-living systems also need energy to function. o For example, cars and aeroplanes need fuel

to provide them with energy to move.

16.2 Forms of Energy

• Potential Energyo Potential energy is stored energy due to a

body’s position or condition.

16.2 Forms of Energy

• Examples of potential energy:o Chemical potential energy

• Energy stored in fuels such as petrol and food that can be released through chemical reactions.

16.2 Forms of Energy

• Examples of potential energy:o Gravitational potential energy

• Energy that an object has because of its position or location.

• When the object is in a higher position with respect to the ground, it has more gravitational potential energy than in a lower position.

16.2 Forms of Energy

• Examples of potential energy:o Elastic potential energy

• Energy that an object has when it is stretched or compressed.

16.2 Forms of Energy

• Kinetic Energyo Kinetic energy is the energy that a body has

due to its motion.• All moving objects have kinetic energy. • Examples: a bird flying in the sky, a girl walking

down the street and a car speeding down the road.

16.2 Forms of Energy

• Heato Heat is the energy that flows from a

region of higher temperature to one of lower temperature.

• Heat flows from things that are hot. • The Sun is an important source of heat

energy during the day. • Heat is used in homes for cooking, heating

water, ironing clothes.• In factories, heat is needed for processes

like melting metals, creating steam to turn turbines and making chemicals react.

• Lighto Light is the energy that enables us to see.

• Things that are luminous can give out light energy.• The Sun is an important source of light energy during

the day.• Without light, the world would be completely dark, and

we would not be able to see things around us.

16.2 Forms of Energy

16.2 Forms of Energy

• Sound o Sound is the energy produced when objects

vibrate.• Sound allows us to communicate and enjoy music.• Sound is also used as a warning.

– For example, when a fire breaks out, the fire alarm goes off and alerts everyone to get to safety.

16.2 Forms of Energy

• Electricityo Electricity or electrical energy is the energy

that results from the flow of charged particles.• Electricity is a useful form of energy that can be

transformed into many other forms of energy.• Almost all electrical appliances or equipment in

homes and offices need electricity to work.

16.3 Energy Transformations

• Photosynthesis in plants o Light energy Chemical potential energy

16.3 Energy Transformations

• An archer releasing his bow o Elastic potential energy Kinetic energy

16.3 Energy Transformations

• A moving caro Chemical potential energy Kinetic energy +

Sound energy + Light energy + Heat energy

16.3 Energy Transformations

• Generation of electricityo Electricity is a useful form of energy. o Electrical generators are used to convert

kinetic energy to electricity.o Power stations produce large amounts of

electricity needed in homes, schools and offices.

o In a power station, a series of energy changes occur before electricity is produced.

16.3 Energy Transformations

• In a power station

coal supply

cooling water

boiler

steam line turbine

switchyard

generator

condenser

1. A fuel such as coal, oil or natural gas is burnt and heat is produced to boil the water in the boiler.

Chemical potential energy of fuel Heat energy of water

2. The heat energy turns water into steam at high pressure, which goes through the boiler and turns the turbines.

Potential and kinetic energy of steam Kinetic energy of turbines

3. The turbines are connected to a generator, which converts the kinetic energy of the turbine blades into electricity.

Kinetic energy of turbines Electricity

16.3 Energy Transformations

• Generation of electricityo In a nuclear power station, nuclear reactions occur by

bombarding radioactive elements with neutrons. o This creates large amounts of heat to boil the water into

steam to turn turbines.o Nuclear energy in radioactive elements Heat

Kinetic energy of steam Kinetic energy of turbines Electricity

16.4 Law of Conservation of Energy

• Energy transformations in a swing

A

B

C

When the swing is at its highest point, A, it only has gravitational potential energy. When the swing is midway between A and B, some of the gravitational potential energy is converted to kinetic energy.

When the swing is at its lowest point, B, all the gravitational potential energy has been converted to kinetic energy.

16.4 Law of Conservation of Energy

• Energy transformations in a swingo In theory, the child would be able to swing to

and fro for an unlimited period of time.o However, the swing will eventually stop moving if no one gives

it a push every now and then. What happened to the energy?o The law of conservation of energy states that energy can

change from one form to another, but it cannot be created or destroyed.

o When energy is not lost, we say it is conserved. The swing stops moving as the energy was converted to other forms of energy such as heat and sound energy due to friction between the swing and surrounding air.

16.4 Law of Conservation of Energy

• Energy transformations in a ball falling on the floor o Let the total energy

possessed by the ball be E.

o According to the conservation of energy, the total amount of energy, E, does not change.

A

D

C

B

At position A, the ball has potential energy PEA. This is equal to E.

PEA = E

At position B, the ball is falling. It gains kinetic energy, KEB, while losing some potential energy. The potential energy left at position B is PEB .

KEB + PEB = PEA = EAt position C, just before the ball hits the floor, only kinetic energy KEC is left.

KEC = PEC + KEC = PEA

= E

At D, the ball hits the floor and becomes compressed. A sound is heard and heat is produced due to friction.

Elastic potential energy of ball + heat + sound = E

16.4 Law of Conservation of Energy

• Energy transformations in a ball falling on the floor o Then ball is unable to reach

its original height of position A when it bounces back up.

o This is because some of the energy, E, is lost as sound and heat when it hits the floor.

o With less energy, the ball cannot regain its original height.

A

D

C

B

16.5 Conserving Energy

• It is important to conserve energy because most of the energy we use comes from non-renewable resources.

• Non-renewable resources include crude oil and coal. These sources of energy are limited and will run out one day.

Extracting, processing and burning crude oil cause large amounts of pollution, which destroy the environment.

Coal power plants produce more pollution than oil power plants. But coal is more commonly used in developing countries as it is cheaper than oil.

Renewable sources of energy

• Renewable sources of energy are sources of energy that can be sustained or renewed indefinitely, due to unlimited supplies or because of new growth.

Renewable sources of energy

• Solar energy o Solar energy is used in solar furnaces for

smelting iron.o Solar energy is also used to generate steam

in power station. This steam is used to turn turbines of a generator to produce electricity.

• Wind energy o A wind farm is a

collection of wind turbines used to generate electricity.

o The wind turbines use the kinetic energy of the wind to generate electrical energy.

Renewable sources of energy

Renewable sources of energy

• Wave energyo Wave farms use the

kinetic energy of waves to generate electricity.

o The up-and-down movement of the wave will shift gears to turn turbines to generate electricity.

Renewable sources of energy

• Biomasso Biomass refers to plant and animal material

from which we can:• extract oil (oil palm, jatropha, jojoba)• ferment into gas (water hyacinth, manure)• burn (dried plant material, wood, charcoal)

Renewable sources of energy

• Conserving energy in Singaporeo Singapore uses natural gas for its power

stations but has started using solar energy, wind energy and biomass.

o Since Singapore does not have many natural resources, we are dependent on other countries for our fuel needs.

o Hence, it is important for us to be aware of conserving energy.

Renewable sources of energy

• Conserving energy in Singaporeo We should use energy more efficiently and

avoid wasting electricity.o For example, you should turn off electrical

appliances that are not in use.

Miscellaneous

• http://www.eia.doe.gov/kids/energyfacts/science/formsofenergy.html

• http://en.wikipedia.org/wiki/Energy_transformation

• http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/energy/ce.html

• http://fi.edu/guide/hughes/energyconservation.html

• http://www.reupower.com/energysvc/53ways.html• http://www.eia.doe.gov/kids/energyfacts/sources/r

enewable/renewable.html