ENERGY

What is Energy?
 Energy is the property of something that makes it able to apply a force and do work.

 There are two kinds of energy: stored energy and movement energy.

Forms of Energy
 As we know there are two kinds of energy: stored energy and movement energy.

 Stored energy is also known as potential energy. Because it gives something the

potential to use its stored energy,

 Movement energy is also known as kinetic energy. It came from the greek word means

motion.’

There are several forms of each kind of energy

Gravitational Potential Energy

 The force of gravity between an object and the Earth pulls the object towards the centre

of the planet.

 If the object is in a position above the surface of the Earth, they stored energy called

gravitational potential energy.

 Example: There is a plate on a table, this plate is supported by something (table) but if

the support is removed, they will accelerate to the Earth’s surface and their potential

energy will be released and changed into other form.

Strain Energy

 Known as elastic potential energy

 Some material is elastic, which means that they can be easily squashed, stretched or

bent, but still get back into it shape once the force acting on them is removed.
o When their shape is changed by squashing, stretching or bending, they store energy

which will allow them to return to their original shape.

Chemical Energy

 The chemical energy is stored in the links between the atoms.

o The chemicals are made from atom that are linked together to make molecules.

o The energy is released when the links are broken and the molecule (energy stored) is

broken down into smaller molecules.

 Example:

o Carbohydrate are a store of chemical energy in food. During respiration, carbohydrate is

broken down into carbon dioxide (CO2) and water (H2O). The energy that is released in

this process is used by our body.

o Fuel → Heat homes, heat water

Kinetic Energy

 Everything that move has kinetic energy

 When an object with kinetic energy hit another object, a force acts on them both that will

distort the second object or set it moving.

 Example: If you move your foot and kick a ball, the ball moves away.

Sound Energy

 Produced by the vibration of an object.

 Sound energy can passes through solids, liquid, and gases.

 They move back and forth in order way so that the wave spreads out in all direction

from the point when the vibration is produced.

 Example: Playing guitar.

 Electrical current is the movement of electrical charges through a conductor. Where the

electrical charges are given electrical energy by the battery and carry it to the working

part.

 Example: Lamp, the energy changes into light and heat.

Internal Energy

 Also known as thermal energy

 All substance are made up of particles. When the temperature is increase, the

movement is also increase. This is because the particles receive more energy, so that it

will move faster.

Electromagnetic Energy

 There is a form of energy that can travel through space at the speed of light. This

energy has properties such as electricity and magnetism. This is called energy

electromagnetic waves.

o These waves make up rays of light and heat, this form of energy is called radiation

energy

Light Energy

 Light energy is kinetic energy with the ability to make types of light can be detected with

human eyes.

Energy Changes
 When energy is used, it always changes from one form to another and some always

changes into heat energy.

 Example:
o Light: Electrical energy → light energy and heat energy

o Playing drum: Chemical energy → sound energy and movement energy

Wasted Energy

 When we turn on the light, it will change from electrical energy into light energy and heat

energy. In this case, we only use the light energy, so that the heat energy considered as

wasted energy.

 When we use vacuum cleaner, some machine make noises, it wasted the sound

energy.

Fuels

 Substances that are burned to release their chemical energy to provide heat and light

are called fuels.

 Examples: Wood, coal, gas, charcoal, oil, diesel oil, natural gas, wax, etc.

o Some gases and waxes are used to provide light in homes, tents.

o Expand gases in vehicle engines and turn on hot water into steam to generate

electricity.

o Coal, gas, and oil were formed from plants and animals are called fossil fuels.

Fossil Fuels

 Coal is formed from plants that grew up million years ago. When they died, they fell into

the swamps. Because swamps is lack of oxygen, it prevent the bacteria to grow and

decompose the dead plants. Then it will form peat, later the peat became buried and

was squashed by the rocks. The increase in pressure slowly changed the peat into coal.

 The oil and methane gas also formed in the same way. When animal died, they sink to

the ocean floor and the dead plankton that collected on the ocean floor did not
 decompose because the lack of oxygen. Then, the remain formed a layer which

covered the rock. The weight of the rock squeezed the layer and heated it and it

converted the layer of dead plankton into oil and methane gas.

Renewable Resources

 Because fossil fuels need million years to be form, then the supplies of fossil fuels are

limited. By the time goes, there will be not enough to meet our needs.

 Scientist trying to develop renewable resources by:

o Convert the wind into electric energy by using the power plants.

o Using the natural rise and fall of tides by the gravitational interaction between the Earth,

Sun, and Moon (tidal energy).

o Using the movement of water from river (hydroelectricity)

o Using the light of the sun (solar power)

Energy Transfer and Transform

 Example:

o Reading a book with electric light: The electrical energy is being transformed into light

energy.

o To keep our body warm, some of the stored chemical energy is transformed.

Energy Transfer Diagram

 Energy transformation can be shown by energy diagrams. There are 3 parts to an

energy transfer diagram:

o The first object is showing the energy input

o The second object is showing an energy converter or transducer

 Example:

o Blowing up balloon: kinetic energy → ballon → strain energy

o Taking a photograph: light energy → camera → chemical energy

o Releasing a catapult: strain energy → catapult → kinetic energy

Sankey Diagram

 A sankey diagram is a second kind of diagram that shows energy changes

 It features arroes of different width. The width of the arrow indicates the amount of

energy it represent.

 The unit in which energy and work are measured is called the joule (J).

 Example:

Plants and Energy

 Energy stored inside the seed is used as the root grows and seeks out water. Stored

energy is also used by the growing shoot.

 There is a process of making food inside the plant by the light energy

called photosynthesis.
o Some of the light energy falling on the leaves is trapped inside them. It is converted into

stored chemical energy as the plant makes food using water from the soil and carbon

dioxide from the air.

 Then the chemical energy stored in a plant is transferred to a herbivorous animal then

has a store chemical energy which keeps them alive. For carnivorous animal, they feed

on herbivorous animal and stored the chemical energy.

o Thus chemical energy that stored in animal are all came from the light energy that

trapped in plant.

Human and Energy

 The chemical energy in food is released in a process called respiration.

o When the energy is released, carbon dioxide and water are produced. The carbon

dioxide is released into the air when we breathe out. The water is used in our body or

released in swear and urine.

 Most of the energy that released in our body is used for movement and to keep our

body temperature constant.

The Difference Between Conduction, Convection,

 There are types of heat transfer

Conduction

 The transfer of energy by direct contact.

o This transfer occurs when molecules hit against each other.

 Happened due to the difference in temperature

have simple molecules (example: metals).

 Heat transfer in conduction is pretty slow.

Convection

 Convection is the movement of heat by a fluid such as water or air.

o The fluid (liquid or gas) moves from one location to another, transferring heat along with

it.

 Happened due to the difference in density.

 Heat transfer in convection is faster than conduction.

 Heat transfer occurs through intermediate objects.

o For example, steaming cup of hot tea.

Radiation

 Radiation is the transfer of heat by electromagnetic waves.

 In addition to the sun, light bulbs, irons, and toasters also transfer heat via radiation.

 Heat transfer by radiation does not need any matter to help with the transfer.

 Heat transfer in radiation is the fastest among all.

 The heat transfer occurs in all objects with a temperature greater than 0 K.

Energy Resource
What is Energy Resource?

 An energy resource is anything from which one can obtain energy.

 Most the energy comes from fossil fuels. These are coal, oil, and natural gas.

Fossil Fuels
 Fossil fuels are stores of chemical energy. The energy is released when the fuel is

burnt.

o Ex: In a car engine, petrol and air are mixed together. A spark ignites the mixture and it

burnt. The energy released makes the car move forward.

 Fossil fuels are found underground. Coal is formed from the remains of plants that died

millions of years ago. Oil and gas formed from the remains of sea creatures.

Generating Electricity

 Electricity is a convenient way of sending energy from place to place. Most electricity is

generated in power stations which burn fossil fuels, especially coal and gas.

The Difference Between Evaporation and Boiling

 Evaporation is a bit different from boiling.

o The temperature of the water doesn’t have to reach 100°C. Even when the temperature

is quite low, the water gradually turns into water vapor in the air.

Evaporation Cools You Down

 On a very sunny day, you may get too hot. One way to cool down is to get wet.

o When you get out, the water evaporated off your skin, and this cools you down. If there

is a breeze blowing, the water will evaporate more quickly and you will cool down

rapidly.

Evaporation and Energy

 When water evaporates from your body, it carries energy away. That is why you feel

cooler.
 Evaporation has a cooling effect due to the particles in water moving around. Some

have energy to escape from the surface, they become water vapor in the air.

o The particles with the most energy are the ones that escape. The ones with less energy

is left behind, so the water is colder than before. Its temperature decrease