CONCEPT OF ENERGY

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Science: Grade 5 Energy and Change: Concept of Energy

CONCEPT OF ENERGY

What is Energy?

Energy is defined by scientists as “

the ability to do work

.” Energy cannot be seen as it is invisible. It is stored inside things. For example, paper is a fuel, because when you light it, it releases (gives off) heat energy. Anything that burns is a fuel.

Paper is a Fuel Wood is a Fuel

The Sun is the most important source of energy. The energy of the Sun reaches Earth in the form of radiation, light and heat. Version 1: December 2013 © Copyright My Cyberwall 1

Science: Grade 5 Energy and Change: Concept of Energy We use energy to provide light and heat in our homes, to run our appliances, to run machines in industry and for transport.

Energy for Lighting Energy for Heating Energy for Running Appliances

A fire is the result of energy being released when oxygen combines with the fuel which is being burned.

A Fire

Depriving a fire of oxygen will eventually stop it from burning. An example of this is a candle placed under a glass, the candle will go out once it has used up all the oxygen. Since the Stone Age, fire has been used to provide food and light.

Fire Provides Heat and Light

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Science: Grade 5 Energy and Change: Concept of Energy Wind has also been used to sail ships, for windmills to grind grain, saw wood and pump water.

Sailing Ship Windmill

The Industrial Revolution in the second half of the 18 th Century saw the wide scale use of fossil fuels in steam engines.

Vintage Steam Engine

Energy is used in the following ways:

For Growth

All living things need energy to grow and survive. Plants use sunlight for energy. Animals and humans eat plants and use the energy stored in them. Version 1: December 2013

Plants Use the Suns Energy

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Science: Grade 5 Energy and Change: Concept of Energy The Sun’s energy is taken up by the plant and stored in food. Energy is therefore in food in a stored form. Animals and people eat the plant for nourishment and use the energy.

For Growth - Food Contains Stored Energy

Plants from millions of years ago that were not eaten by animals changed into coal. Stored energy therefore also occurs in coal and oil.

Coal Contains Stored Energy Oil Contains Stored Energy

For Light

Light is a type of energy that we use all the time. During the day, we use light from the Sun, called natural light. When it’s dark, we use electrical energy for light. Batteries are a source of energy that can be used to power torches and flashlights. Version 1: December 2013

For Light – Batteries are a Source of Energy

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Science: Grade 5 Energy and Change: Concept of Energy

For Heat

Energy is used to make heat. We burn wood and gas to cook and heat our homes. Electricity is also used to make heat.

For Heat - Electric Heater

For Movement

Energy is used to make things move, for example, cars that use petrol, toys that use the energy in batteries and sailboats that use the energy from the wind.

For Movement - Cars Use Petrol

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For Movement - Toys Use Batteries

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Science: Grade 5 Energy and Change: Concept of Energy

Machines

We need energy in the form of electrical energy to make appliances and machines work, for example, TVs and computers.

Electrical Energy – Computer Electrical Energy –TV

When we use energy, we change it from one form into another. For example, when we burn wood or fuel, we convert its energy to heat and light. When we drive a car, we change the energy from the petrol to heat and movement. So energy can be changed from one form to another, but cannot be destroyed.

Renewable and Non-Renewable Energy Sources

Energy comes from several different sources, for example, gas, oil and coal (known as fossil fuels), nuclear power, wind power, solar power, and hydroelectric power.

Oil Nuclear Power Station

Some of these energy sources are

renewable

and some are

non-renewable

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Science: Grade 5 Energy and Change: Concept of Energy

Renewable Sources of Energy

Renewable

means that they can be replaced (not re-used) and will not run out. These sources can be replenished or made again in a short period of time. Examples of renewable energy sources:

Biomass

This type of energy comes from living things. The energy that is stored in living organisms comes originally from the Sun.

Biomass - Elephant Dung

Biomass

is a form of energy using the material of living things such as animal droppings and other decayed plant matter which produce methane gas (known as biogas) which can be burnt to provide heat and electricity. It is burned in the same way as natural gas. Dried elephant dung is an ideal fuel for burning at a low, constant temperature and can be used as cooking fuel. Chicken droppings are another source of biomass.

Wind Power

This is energy from moving air. Wind power can be harnessed through wind turbines, in the same way that windmills have been used for thousands of years. The turbine harnesses the energy in wind converting it into electrical energy. Version 1: December 2013

Wind Turbines

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Science: Grade 5 Energy and Change: Concept of Energy However, wind turbines are unsightly and can be expensive. They only work in areas which are very windy.

Water Power

Water that moves can also be made into electricity in the following ways: 

Hydroelectric

power uses fast flowing rivers to create energy. It is a renewable source of energy which does not pollute or use up any resources. Norway is one country that produces 99% of its electricity through hydroelectric power. Tidal barrages are also a form of hydroelectric power and are built in the mouths of rivers, so that when the tide turns, the energy is harnessed.

Hydroelectric Power

Wave energy

can be harnessed to produce electricity through tidal flows. This type of energy can only be made for 6 to 12 hours a day when the tide is flowing the fastest.

Tidal Power Station

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Science: Grade 5 Energy and Change: Concept of Energy

Geothermal Power

Geothermal energy is made from heat inside the Earth. At the Earth’s core, the temperature is more than 5 000 °C. At the surface, the average temperature is 15 °C and for every 100 metres we drill down, the temperature increases by 1 - 2 °C, depending on location.

Drilling For Geothermal Power

Solar Power

Solar power is energy from the sun and works through solar panels made of silicone, which soak up the Sun’s ray and turn them into electricity. This energy converts the light from the Sun into electrical energy.

Solar Power Station

As the world’s energy consumption is increasing by over 2% per year, most countries are looking at using more renewable energy sources. Version 1: December 2013 © Copyright My Cyberwall 9

Science: Grade 5 Energy and Change: Concept of Energy

Non-Renewable Sources of Energy

Over 85% of the world’s energy is made from

non-renewable

sources. These are known as

fossil fuels

because, like fossils, they have been formed over millions of years from the remains of living things. These include oil, coal and gas. Oil is in liquid form, coal is a solid and natural gas is a gas.

Oil Coal Gas

Non-renewable energy sources cannot be replaced when they are used up. Coal is made from the remains of plants and oil and gas are made from dead sea creatures. The energy stored in fossil fuels came originally from sunlight. When the living things that made them died, they were buried over long periods of time by layers of rock. They were heated by chemical processes taking place, as well as pressure and so changed to fossil fuels. Fossil fuels contain high percentages of carbon and when they are burned, they release carbon dioxide into the atmosphere. Carbon dioxide is a

greenhouse gas

that contributes to global warming.

Pollution

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Science: Grade 5 Energy and Change: Concept of Energy

Nuclear energy

is the fourth type of non-renewable energy source. Nuclear power is a type of energy made from splitting atoms to produce energy, which is turned into electricity. Making nuclear power creates toxic waste which can be accidently released into the atmosphere.

Nuclear Power Station

Forms of Energy

There are two main forms of energy, i.e:

1. Potential Energy

This is energy that is stored and waiting to be released and includes:

Chemical energy

– for example coal, gas, oil, biomass and the energy in food. Energy is also stored in electrical cells (batteries) as chemical energy. When the cell is connected to a light bulb, energy is released.

Chemical Energy – Battery

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Science: Grade 5 Energy and Change: Concept of Energy

Gravitational energy

– this is energy stored at the height of an object. The higher and heavier the object, the more gravitational energy it will have. For example, a rollercoaster picks up speed from gravitational energy as it goes downwards and converts it to motion energy to get up the next hill. Hydropower is a form of gravitational energy when water from a river flows into a reservoir and builds up behind the dam wall.

Gravitational Energy - Roller Coaster

Mechanical energy

– this is energy stored in objects by tension, for example, a compressed spring or a stretched rubber band. Winding up a clockwork toy releases the mechanical energy. A bow and arrow works in the same way. Energy is stored by bending and then releasing the bow.

Mechanical Energy - Bow and Arrow

Nuclear energy

– this is energy stored in the nucleus of an atom, for example in uranium atoms. The nucleus can store a huge amount of energy. This is used in power stations to make energy. Version 1: December 2013

Nuclear Energy - Nuclear Missile

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Science: Grade 5 Energy and Change: Concept of Energy

Electrical energy

– this is energy found in nature, for example, lightning. The electricity in our homes is also a form of electrical energy.

Electrical Energy

Magnetic energy

– the north pole of one magnet is strongly attracted to the south pole of another magnet. Magnetic energy can be converted to electrical energy through electromagnetism.

Magnetic Energy – Compass

Elastic energy

– this is the energy that is stored in elastic bands and springs, by compressing or stretching an object.

Elastic Energy – Catapult

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Science: Grade 5 Energy and Change: Concept of Energy

2. Kinetic Energy

Anything that moves has

kinetic energy

. The faster it moves and the heavier it is, the more kinetic energy it has. Examples of kinetic energy include:

Radiant energy

- for example, light and sunshine.

Solar Panels

Thermal energy

- for example geothermal energy. Version 1: December 2013

Geothermal Power Station – Iceland, Wikipedia Creative Commons Attribution Share-Alike: Gretar Ivarsson

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Science: Grade 5 Energy and Change: Concept of Energy

Motion energy

- this is energy stored in the movement of objects, such as wind.

Kite-Surfing using Wind Energy

Sound energy

- this is energy carried by sound waves.

Energy in Sound Waves

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