Make study notes of everything: 1















Contents
Topic 1 A and B: Potential and Kinetic Energy ....................................................................3
Sources of energy............................................................................................................3
Renewable and Non-renewable sources of energy......................................................3
What is Kinetic Energy?................................................................................................3
Different types of potential energy....................................................................................4
Elastic potential energy.................................................................................................4
Activity 1.......................................................................................................................5
Potential energy in food................................................................................................5
Activity 2.......................................................................................................................6
Write down the energy values of types of food.............................................................6
Energy is needed to make everything work, move or live ................................................6
Sources of energy............................................................................................................6
Topic 2: Non- renewable energy sources ............................................................................7
Fossil fuels.......................................................................................................................7
Coal..................................................................................................................................8
Oil and gas.......................................................................................................................8
Interesting Fact.............................................................................................................9
Energy from nuclear fuels ................................................................................................9
Facts about Uranium......................................................................................................10
Activity 3.....................................................................................................................10
Topic 3: Renewable sources of energy..............................................................................11
Hydro (water) energy......................................................................................................11
Wind energy...................................................................................................................11
Solar energy...................................................................................................................12
Bio-fuel...........................................................................................................................12
Activity 4.....................................................................................................................13
Topic 4: Law of Conservation & Energy Transfers – Conduction, Convection, Radiation..13
LAW OF CONSERVATION OF ENERGY......................................................................13

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Types of energy systems ...............................................................................................15
Mechanical systems ...................................................................................................15
Thermal systems ........................................................................................................15
Electrical systems.......................................................................................................15
Biological systems......................................................................................................15
Heating as a transfer of energy......................................................................................15
Conduction .................................................................................................................15
Convection..................................................................................................................16
Radiation ....................................................................................................................16
Activity 5.....................................................................................................................17
Using Insulation Materials..............................................................................................17
Uses of insulators.......................................................................................................18
Insulating the ceilings of buildings: Ceiling insulation................................................18
Insulating cooler boxes and flasks..............................................................................18
Indigenous building design.............................................................................................19
Useful and wasted energy..............................................................................................19
Clothing ......................................................................................................................19
Conservation of heat in the home...............................................................................20
Activity 6.....................................................................................................................20
List the appliances and the input, output ad wasted energy.......................................20
Energy transfers in the National Grid .............................................................................21
Generating electricity from energy sources....................................................................21
Electricity transmission and distribution..........................................................................21
Dynamos........................................................................................................................21
Careers in electricity power generation..........................................................................22
Activity 7.....................................................................................................................23



















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Topic 1 A and B: Potential and Kinetic Energy



Energy works in a system. Energy can be transferred in the system, but the total amount of energy will remain the same. This is known as the Law of Conservation of energy. Energy can be in the form of potential or kinetic energy. There are different types of energy, such as heat, electrical and light energy. Energy can change from one type to another, such as, when we switch on an oven, electrical energy goes into the oven through the element and changes into heat energy when the oven is warm.


Sources of energy

Renewable and Non-renewable sources of energy

The word ‘work’ is used to describe a number of different activities. When you sit down at

home to do your homework, you can say that you are ‘working’. When a person leaves their house in the morning, they might say that they are ‘going to work’. But, in a scientific context, ‘work’ has a very precise meaning. The mother, in Figure 1, is pushing the trolley. In a scientific sense, she is ‘working’ the trolley. In other words, when you push or pull something and make it move you are doing ‘work’ on that specific thing.






Figure 1








What is Kinetic Energy?

Kinetic energy causes a change or movement. A moving object can cause a stationary

object to move. Some examples of kinetic energy are: a stretched elastic band which is released; a weight that falls off a table; water stored in a dam falls through a chute to drive a turbine; wind blows and turns a wind pump, a motor car turns the wheels; electricity flowing through a light bulb (also called electrical energy); the fast-moving water particles



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in boiling water (also called heat energy). Sometimes you cannot see the movement

caused by kinetic energy, but you will notice a change in the object.











Different types of potential energy

Elastic potential energy

When we use the word “potential” in everyday life, it refers to something that is not

happening now, but it is likely to happen in the future, like stretching an elastic band slightly.







The elastic band now has potential energy. Stretch it a little more. The elastic band now has more potential energy. As you keep stretching it, the potential energy increases. When you release the elastic band, it no longer has potential energy. However, the energy is not lost; it has simply been converted into another type of energy. Anything that can be stretched, squeezed (like a rubber ball) or wound up (like the spring of a jack in a box) has elastic potential energy.










https://www.youtube.com/watch?v=Q1VoK0Ga36w

Use this link to connect to an interesting experiment using potential energy with elastic bands and a watermelon.



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Activity 1

Answer these questions in your book:


1. Define the word “energy”.	(1) 2. Explain what an energy system is.	(1) 3. Explain in a sentence using your own words, what potential energy is and give an
example.	(2) 4. Define the word “kinetic” energy.	(2) 5. What kind of energy is found in a torch battery?	(1) 6. If an athlete drinks an energy drink, what happens in the athlete’s body?	(2) 7. If a child is sliding down a slide, what energy is used?	(1)
Total: 10


Potential energy in food

If you hold a loaf of bread or a bag of oranges, you are holding potential energy. The food you eat has potential energy that is released in your body when you eat it. The energy content in food should be listed on the packaging of the food. Look for the table of typical information and then look for the energy value. The unit of measurement for energy is the joule, which is named after James Prescott Joule, an English physicist who worked in the field of energy and heat. The symbol for joule is J. The joule is quite a small unit of measurement and so energy measurements for food are generally given in kilojoules (kJ). One kilojoule is equal to 1000 J.


By law, a food can only be labelled as “low in energy” if it contains than 170 kJ per 100g

(solid foods) or 80 kJ per 100 ml (liquids). A food can only be labelled as “high in energy” if it contains more than 950 kJ per 100g or 250 kJ per 100 ml.














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Activity 2

Write down the energy values of types of food.

1. Write down the energy values in kJ per 100 g of solid foods or per 100 ml of liquid of at least five different types of food. Examine the labels on foods that you have at home. Look at cereal boxes, milk bottles, fruit juice bottles, tinned foods, sweets, chocolates. Try to find a wide range of foods for this activity (carbohydrates, proteins, fruits and vegetables, fats and oils, and even junk foods like crisps and fizzy drinks).
2. Draw up a list, and categorise the foods in your sample, of the types of food and their energy content, ranked from highest to lowest. Compare it with other learners’ lists in the next lesson. Which food has the highest energy content?


Energy is needed to make everything work, move or live

When a locomotive pulls a train, it is doing work on the train to make it move. When you

kick a ball, you are doing work on the ball to make the ball move. When you switch on a light, work is being done to make electricity flow through the bulb. When you run, your muscles are doing work to make your body move.


Now that you have an understanding of what is meant by ‘work’ let’s examine what is meant by the word ‘energy’? Energy is what is needed to do work – to make things move, to make things change and to make things grow or stay alive.




An	old	fashioned	steam	driven

locomotive train






Sources of energy

We call something a ‘source of energy’ when that object or substance has stored energy that is (dormant/sleeping). Usually, something has to be done to the ‘source of energy’ for it to release the energy (make something happen). For example, coal is a ‘source of energy’ because it has energy that is waiting to be used. Its energy is only released when


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it is heated enough for it to burn. It then releases energy in the form of heat and light.

Stored energy is called potential energy.















Anthracite is a form of coal. It has the highest potential energy of all the types of coal.
Coal is a type of fossil fuel, i.e. it has been formed by nature over a long time.



The Sun contains stored energy as well - energy is stored in the hydrogen gas that makes

up most of the Sun. This energy is constantly being changed into heat and light energy in a reaction that changes hydrogen into helium. We use helium in hot air balloons and party balloons.
















Topic 2: Non- renewable energy sources



Fossil fuels

Fossil fuels are things such as coal, oil and natural gas. Oil and gas supply about one half of the world’s energy needs and coal supplies about a quarter. More than half the coal in


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the world is burnt to produce electricity. A fossil fuel is a non-renewable source of energy.

It has been formed over millions of years and cannot be replenished (replaced).













Coal

Millions of years ago, the plants in swamps absorbed energy from the sun. As these plants died, sand rock and other substances covered the remains of the dead plants. Over millions of years, the weight of the substances lying on the dead matter created pressure that compressed the substances. A substance called peat was formed as a result of this pressure. The peat was then pushed towards the hot centre of the Earth and this heat changed the peat into fossil fuels. The compression process on plant matter resulted in coal being formed. (The compression of other substances resulted in the formation of fossil fuels such as natural gas and oil).



















Oil and gas

Crude oil and natural gas are often found together underground. These fossil fuels can be extracted by drilling into the ground and then storing the crude oil and gas that rises to the top. Crude oil is

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refined to make petroleum (petrol) and diesel for vehicles and jet fuel for aeroplanes. It is

also used to make plastic products. Oil can be burnt to generate electricity.


Natural gas is pumped from underground and is then processed so that it can be used as a fuel. Generally, people use gas bottles to store natural gas for use in the home. These gas bottles are connected to lighting, heating and cooking equipment, which allows the gas to be burnt. A Bunsen burner is connected to a natural gas source. Some countries have a natural gas supply, which supplies natural gas directly to households. Natural gas can also be used to generate electricity.


Interesting Fact

Vaseline is made from petroleum jelly (petrol jelly).


Energy from nuclear fuels

Uranium is a nuclear fuel. Nuclear fuels can

convert their nuclear energy into heat energy without having to be burnt. This energy conversion (change) happens in a special chamber called a nuclear reactor and the heat that is given off is eventually converted into electrical energy.


In South Africa, we generate just over five per cent of our electricity using nuclear energy. Currently, the Koeberg Nuclear power station near Cape Town is South Africa’s only nuclear power station and it has two nuclear reactors.


Nuclear energy does not cause air pollution, but the waste products are dangerous to human, animal and plant life. At present, it is difficult to get rid of these waste products. Nuclear power stations also need uranium, which must be mined. Uranium mining has a similar environmental impact to gold mining. The fact that uranium is needed for nuclear energy means that nuclear energy is non-renewable.





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Facts about Uranium


Uranium is a very heavy metal which can be used as an abundant source of concentrated energy. Uranium occurs as common tin in the Earth's crust. Uranium is found in seawater, and can be recovered from the oceans.	Uranium	was discovered	in 1789 by Martin Klaproth, a German chemist, in the mineral called pitchblende. It was named after the planet Uranus, which had been discovered eight years earlier.



Uranium was apparently formed in supernovas about 6.6 billion years ago. While it is not common in the solar system, today its slow radioactive decay provides the main source of heat inside the Earth. Uranium has a melting point of 1132°C. The chemical symbol for uranium is U. Uranium is a radioactive metal and the radiation that it emits can be very harmful to plants and animals.


Activity 3

Answer these questions in your books. Peer mark.

1. Explain why fossil fuels and nuclear fuels are regarded as non-renewable.	(2) 2. What is a fossil fuel?	(2) 3. Name three uses of fossil fuels.	(3) 4. Explain, in a point-form list, how fossil fuels are formed.	(5) 5. Give a basic explanation of how electricity is generated in a nuclear power station? (4) 6. Give the name of South Africa’s nuclear power station and say where it is located. (2)
7. Say whether you agree or disagree with this statement and explain your opinion:	(2) Nuclear power stations are more environmentally friendly than coal-fired power stations.                                                                                                                    Total: 20

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Topic 3: Renewable sources of energy




Energy sources that are naturally restored or replaced, after we use them, are called renewable sources of energy. These sources cause less or no pollution of the atmosphere or environment than the use of non-renewable sources. Renewable sources of energy are continually replenished. They include hydro power (water power), wind, sunlight and bio-fuel such as wood.


Hydro (water) energy

Water stored in a dam can run through a channel where it turns a turbine which turns a generator to produce electricity.










A water turbine is made so that it turns when water runs through one side of it.









Wind energy

Different parts of the atmosphere have different temperatures. This causes	air currents

(wind). People have used wind as a source of energy for a long time – a windmill is an example of this type of energy generation.




Images of windmill and wind turbines


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A wind turbine is similar to a propeller which turns when wind blows through it. It can be

connected to a generator to produce electricity. Solar energy
Sunlight shining on a solar panel provides energy to push electric charge from one part of the panel to another. Electricity can then flow through a battery to charge it. If there are sufficient panels and batteries, enough energy can be generated to provide power for a small house.


Heat from the Sun can also heat up water running through black tubing on the roof of a house. The hot water is fed into a tank and can then provide hot water for a household.















Bio-fuel

Liquid bio-fuel can be made from crops like maize and soya beans. These crops are fermented so that the sugars in the crops turn into a substance called ethanol. Ethanol can be used as a fuel for cars, on its own, or it can be added to petrol or diesel. Bio-fuel is considered renewable because the supply of crops can be replenished by planting a new crop each year.











Maize	Soya beans


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Wood is also an example of bio-fuel, because, when it is burnt, it releases heat. As a

naturally occurring fuel, wood is relatively cheap and accessible. Like other bio-fuels, it can be replenished by planting more trees.












Activity 4

Answer the questions and choose a peer and mark each other’s work

1. What is a renewable source of energy?                                                              (1) 2. Give a definition of renewable and non-renewable sources of energy.               (2)
3. Make a list of non-renewable energy sources and explain why they are regarded as non-renewable.	(3)
4. We rely on fossil fuels to supply most of our energy needs.

Explain why this is a problem.	(2) 5. Give one disadvantage of relying on wind energy for electricity.	(1) 6. What is hydropower? Explain.	(1)


Total mark: 10


Topic 4: Law of Conservation & Energy Transfers – Conduction, Convection, Radiation.



LAW OF CONSERVATION OF ENERGY

The Law of Conservation of Energy states that: •	Energy cannot be created.
•	Energy cannot be destroyed.

•	Energy can only be changed from one form into another.




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In each system there is an input energy, one or more energy transfers and output energy.

A system is a set of parts that work together. Because a system is a set of parts working together, a change to one part of the system can affect other parts of the system. In the torch, the energy is transferred which turns into light.

















To explain how energy is transferred in a system you need to answer these 3 important

questions:


•	Where does the input energy come from? This refers to the potential energy that start the energy transfer. The boy’s arms, legs and feet.
•	Where does the energy go? From the boy’s legs into the feet and arms moving.

•	 What energy changes are observed in the system? The boy will start running slowly and then run faster.
Examples:

A boy running …	An archer shooting an arrow







A horse pulling a cart










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Types of energy systems

Mechanical systems

Example: A pair of scissors used for cutting a paper, a bent ruler can flick a pellet across

the classroom, a cricket ball hit by a bat.


Thermal systems

Example: a candle heating cold water in a can, a cup of tea losing heat to the

surroundings.


Electrical systems

Example: a cell/ battery in a circuit can activate a motor, buzzer or a small torch bulb.


Biological systems

The energy being passed along a food chain.

Example: a horse eats a plant and can move or pull a cart.


Heating as a transfer of energy

Heating is a process in which energy is transferred from a hotter body to a cooler body.

Heat transfer involves the transfer of heat from a hotter object to a colder object. The energy transfer continues until both bodies are at the same temperature. Heat is transferred in three ways by:
Conduction Convection Radiation Conduction
This is a form of heat transfer that occurs:

•	between two objects when they are in direct physical contact where heat moves from the hotter object to the cooler object or
•	in one object where the heat moves from the hotter part of that object to a cooler part of

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Convection

Convection is the transfer of heat by the movement of liquid or gas particles. When air is

heated, it moves up, and when it is cooled, it moves down. This creates the convection currents. An example of convection is when you boil water in a kettle. The water will slowly, heat up all the liquid and the kettle boils).









Radiation

Radiation carries heat across an empty space (therefore, it has no need for direct contact for the heating of liquid and gas particles). The sun radiates heat across space to heat up the earth. Radiated heat can be absorbed or reflected. Dark colours absorb heat whereas light colours reflect it.













Look at the diagram on the next page. It shows convection currents in a room.

•	The radiator heats the air.

•	The hot air rises and spreads along the ceiling.

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•	As it moves along the ceiling, it starts to get cooler.

•	The air sinks because it is cool, but also because it is pushed by new hot air coming

from the fire place to heat up the earth. Radiated heat can be absorbed or reflected. Dark colours absorb heat whereas light colours reflect it. The original air (now cool) is pushed along the floor by the convection current.
•	When the air reaches the fireplace, it warms it up again, expands, and rises. The convection current continues until the room is heated evenly.















Activity 5

Answer the questions in your workbooks and ask a peer in your class to mark it

according to a given memo

1. Describe how heat is transferred by conduction.	(3)

2. Explain how the heat is transferred from a hot stove to the food in a stainless steel pot.

3. What is convection?	(2)

4. Explain how heat transfer by radiation occurs.	(2)

5. Convection can occur in solids. True or False. Explain your answer.	(2)

Explain why it is best to place heaters near the floor and why an air conditioner is best

placed near the ceiling. Draw and label a diagram to explain this.                           (4) Total: 15


Using Insulation Materials

Heat insulators are good for keeping cold items cold (they slow down heat transfer from the surroundings) and hot items hot (they slow down heat transfer into the cooler surroundings). Good insulators are poor conductors and are therefore non- metals.



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Uses of insulators

Insulators are used in houses to minimise heat loss in winter or heat gain in summer. Poor conductors, such as concrete and bricks, are normally used.


Insulating the ceilings of buildings: Ceiling insulation

Insulation in the roof forces hot air to circulate in the house and not escape via conduction

through the roof.


Insulating the ceiling of homes prevents the warm air from escaping through the roof of the house. Foam can be sprayed above the ceilings in the roof structure or blanket insulation can be rolled out.












Warm air can escape through cracks or gaps and cold air can enter the same way. Repairs should always be done to conserve heat. Houses should also be built in a way to allow the maximum amount of radiated heat from the sun to enter the home. In winter, the corrugated iron will conduct the heat from inside the home, causing it to become colder.


Insulating cooler boxes and flasks


Cooler boxes

A cooler box can be used to keep food cold. Usually, an ice pack is frozen and placed in the cooler box along with the food. The box has a plastic inner wall and outer wall, separated by an insulating material. This is usually foam with air pockets. Styrofoam and plastic are good insulators. Vacuum flasks work in the same way, but they trap heat.

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Indigenous building design

Indigenous people of South Africa build traditional homes to suit the climate. They use

insulation techniques to retain heat in the winter and keep heat out during the summer.


Roofs are made of grass - an excellent natural insulator. Some walls are also made of grass. Other walls are made of mud smeared onto a wooden framework – also well insulated. There are often no windows or openings other than the entrance. Floors are often made of pressed and smoothed cow dung. It dries to form a hard, water-proof floor that is well insulated by the air trapped between the undigested grass pieces in the dung. The cone shaped roof helps to trap the heat.


Useful and wasted energy

Energy cannot be created or destroyed BUT it can be wasted. This happens when energy is converted into energy that is not needed such as heat energy when the object does not require heat energy. This wasted energy escapes into the surroundings.


Clothing

You keep warm by wearing “warm” clothing such as a woollen jersey. There is nothing ‘warm’ about a jersey. It is the same temperature as its surroundings. The jersey keeps you warm by preventing the heat from escaping from your body. To prevent heat loss from your body, during winter, you make use of coats and
jackets. Heat can be lost from our bodies and from appliances such as electric geysers. Remember that energy cannot really be lost, so when you hear the term ‘heat loss’, you should understand that the heat is lost from one object, but that it is transferred somewhere else, often into the air surrounding the object. Heat loss can occur through conduction, convection and radiation.

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Conservation of heat in the home

Conservation of heat energy in homes and buildings can be improved by minimising heat loss in winter and heat gain in summer, by using heaters to warm a house in cold weather and using air conditioning systems in summer to keep the house cool. In addition to ceilings, there are four other areas in a house where insulation can reduce heat transfer: the walls; glass windows; gaps around openings such as doors and windows and metal water pipes.


Electric geysers use electricity to heat water. Solar

geysers use the heat of the Sun to heat water. Heat can be lost from a geyser (through the casing of the geyser), by convection (through the air surrounding the geyser) and by radiation. Many homes in informal settlements are made from corrugated iron. Because iron is a good conductor of heat, the house will become very hot in the summer.



Using electricity wisely
Turn off appliances when not in use.
Turn off lights when not needed or when you are not in that room. Make use of energy saving light bulbs.
Boil only the amount of water required, do not boil a full kettle if you require one cup. Use insulating clothing to keep warm rather than using a heater.
Insulate you house by sealing gaps etc.
Use solar power, or any renewable energy source, whenever possible



• • •
• •
•
•








Activity 6

List the appliances and the input, output and wasted energy

List at least 4 appliances and give ways in which the energy is used correctly for the job and what energy is created that is not needed. List the input, output and wasted energy. For example, when I use a drill to make a hole in the wall I am using mechanical energy BUT the more the drill goes in the wall the hotter the drill becomes. Obviously I do not need heat to make the hole in the wall and therefore the energy wasted is in the form of heat energy.


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Example

Drill…

Input – electrical energy →


Energy transfers in the National Grid

The national electricity grid is a huge national energy circuit. Electricity first gets

generated, then transmitted across power lines and then distributed among consumers of electricity.


Generating electricity from energy sources

Coal, oil, gas, nuclear material, wind water and solar power can be used to generate electricity. In coal-fired power stations coal is ground into a powder and burned to release heat energy to heat up water in a boiler. The water in the boiler turns to steam which then is used to turn a turbine to generate electricity.














Electricity transmission and distribution

Once the energy has been generated it needs to get to the consumers. This is known as

transmission and distribution. The electricity is carried along large conducting cables, supported by pylons, across the country (this is the transmission phase). The distribution phase begins when the electricity reaches a distribution substation where electricity gets distributed to households, plugs, etc.


Dynamos

Dynamos are small generators which convert mechanical energy into electrical energy. This is useful when the

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appliance needs a small current, e.g. when a light on a bicycle gets charged by the

movement of the wheels or a machine for converting mechanical energy into electrical energy, typically by means of rotating coils of copper wire in a magnetic field.
One way to save electricity is to install a solar geyser that can use the Sun’s energy to heat water. These solar geyser heating systems are usually placed on the roof of a house. The system involves the transfer of heat from the Sun to the water in the geyser by radiation, conduction and convection.


Look at the following websites to see how a solar geyser system works and look at pictures and diagrams of solar systems:
www.science.howstuffworks.com/environmental/green.../solar-water-heater.html www.geogroup.co.za/.../fact_sheet_-_how_does_solar_water_heating_work.





















Black tubes absorb the radiant heat from the Sun and conduct the heat to the water in the tubes. Water, close to the upper surface of the tubes, is heated most. It expands and rises up to the tube as shown in the figure 2. Cooler water from the tank sinks into a tube. Convection current is set up with water circulating and getting warmer all the time.


Careers in electricity power generation

An artisan specialises in a trade and has the practical skills required for that trade. A technician operates and maintains technical equipment. Both artisans and technicians


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have promising careers in the power generation industry. Jobs include electricians,

boilermakers, fitters and maintenance personnel.













Activity 7

Answer the following questions in your workbook. Ask a peer, in your class, to mark it for you, using a given memo
1. Explain why brick and concrete are good building materials to use when building a house.	(2)
2. Explain why spongy or foamy materials are good insulators of heat.                   (2) 3. How can a thick coat keep you warm on a cold day?                                           (1)
4. Imagine you were building your own house. Name three things you could do to make sure that the house gets plenty of solar heat.	(3)
5. Explain why thatch is a good choice of building material.	(1)

6. What could the people living in a corrugated iron house do to make the house warmer in winter?	(3)
7. What is a dynamo?	(2) 8. Identify and describe at least 3 ways to conserve energy in your home, school or
community.	(6) 9. Describe the structure of a turbine.	(2)
10.What is the gas that rises from the cooling towers of a power station?

11.Explain how this gas is formed.
(1)

(2)

Total: 25











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