Notes Oxford Science 5th Revised Edition Old Version
Notes Oxford Science 5th Revised Edition Old Version
Part 1: Ourselves
Unit 1: All about the body (pages 1-3 of Pupil’s Book)
Questions (page 3)
A1 Which system is the stomach a part of?
The digestive system.
2 Which system are the biceps and triceps a part of?
The muscular system.
3 What are your tissues and organs made up of?
Cells of different kinds.
5 Give some examples of involuntary muscles in the body.
The cardiac muscle and visceral muscles. (The children need not learn this word now.) Cardiac simply means of the heart, and visceral muscles are those which are found in the internal organs of the body (the brain, heart, liver, the intestines). They are involuntary muscles, and are stimulated by nerves.
4 What kind of muscle is the heart made from?
Cardiac muscle.
6 Which part of the heart sends blood to the lungs?
The right ventricle.
7 How big is an adult’s heart?
B1 Why are the walls of the ventricles thicker than those of the
atria?
The blood from the ventricles has to be forced out of the heart to all parts of the body. The pressure here is quite great, so the walls have to be thick.
2 In which part of the heart is there oxygenated blood?
(Oxygenated means mixed with oxygen)
Blood that comes from the lungs has been oxygenated. Oxygenated blood comes into the left atrium. (Be sure to point out which is left and which is right in any diagram of the heart. Also note: the singular of atria is atrium).
Unit 2: The brain (pages 4-5)
Questions (page 5)
1 What can the brain do that a computer cannot do?
A brain can feel emotions such as anger, jealousy, fear, happiness, excitement, etc.
2 Where is the cerebrum? What happens in the cerebrum?
The cerebrum is the top part of the brain. The cerebrum controls movement (the senses, and association). The cerebrum is the centre for mental activities such as speech, learning, memory and imagination. It also controls all physical activities.
3 What work is done by the cerebellum?
The cerebellum controls movement, balance and coordination.
4 What is important about the medulla?
The medulla deals with involuntary muscles of the body. It is the part of the brain which keeps working even when you are asleep.
5 Which part of your brain helps you to:
a control your breathing medulla
b balance when you are cycling cerebellum
5
c think cerebrum
Unit 3: All about breathing (pages 6-8)
Questions (page 8)
A Copy these sentences into your notebook. Fill in the blank spaces.
1 There are cells in the trachea which produce a sticky liquid called mucus.
2 The diaphragm is a sheet of muscle which separates the 7
lungs from the abdomen.
3 Breathing in and out is called respiration.
4 Trachea is another name for the windpipe.
5 At the ends of the small air tubes in the lungs there are tiny
air sacs which are surrounded by narrow capillaries.
B1 Why are there hairs in your nostrils? Do they behave in the same way as the hairs in the trachea?
The hairs in the nostrils prevent fine particles of dust from entering the windpipe. They act like a filter. The hairs in the windpipe also prevent particles from going to the lungs, but these ripple like waves. They carry the dust back up the throat.
2 Where and how are sounds produced when you talk?
Sounds are produced in the larynx. When air is forced over the stretched vocal cords, sounds are produced.
3 What will happen if you do not take air into your lungs?
You will die. No air in the lungs means that the air sacs cannot absorb the oxygen in the air. The body cannot live without oxygen.
4 Why is smoking harmful?
Smoke from cigarettes contains tar and nicotine. Tar clogs the usual passages, and nicotine is addictive. Smoking causes main diseases such as cancer.
Unit 4: Teeth (pages 09-10)
Question (page 10)
A1 Which teeth are used for chewing and grinding food?
The premolars and molars.
2 What is contained in the pulp of a tooth?
Nerves and blood vessels.
3 What is plaque?
A layer of germs.
4 How is plaque formed?
Plaque (a sticky layer of germs) forms on the teeth if they are not brushed well or cleaned after meals.
B Match the following:
incisor a tooth used for cutting pulp the soft inner part of a tooth dentine the part of a tooth which is like bone dentist a person who repairs damaged teeth
decay rotting of the tooth plaque a thin sticky layer of germs canine tooth used for ripping.
Unit 5: Digestion (pages 11-12)
Questions (page 12)
A1 What is the oesophagus?
The tube which leads down from the mouth to the stomach.
2 What does the liver do?
The liver helps to clean the blood and store food energy.
3 What happens to the food in the small intestine?
The food in the small intestine is made softer by digestive juices. The small intestine absorbs food that the body needs.
4 How does food get to the cells of the body?
The food passes through the thin walls of the small intestine and enters the blood vessels.
5 Where is saliva produced?
Saliva is produced by the salivary glands in the mouth.
6 What do the kidneys help to remove from the body?
The kidneys help to remove waste materials and excess water.
B1 How does drinking liquids help digestion?
Liquids help to make hard food soft. Hard food dissolve more easily in liquids.
2 Why do we sometimes get a pain in the stomach?
By gulping down food too fast, by not chewing food properly and by taking in air as we eat. Some food are not broken down easily, so we have to help our digestive system by chewing food well, eating at regular intervals, not eating too much food of one kind, and by drinking plenty of liquids. We also get a pain in the stomach from food poisoning, i.e. if we eat food which has gone
bad.
3 How long does food take to pass through the body?
Food remains in the stomach for up to four hours, and can remain in the intestines for 36 hours before being passed on the rectum, where it is stored briefly. The time food takes to pass through the system depends on the kind of food being eaten, and the health of the person eating the food.
Unit 6: Food (pages 13-16)
Questions (page 16)
A1 What do proteins do for your body?
Proteins give you energy. They also help to build you up, and make you grow. They enable your body to replace dead cells.
2 How do dietary fibres help the digestive system?
Dietary fibres help to keep the waste moving through the digestive system.
3 How much water do you drink every day? How much water does a person need?
The children should try to work out how many glasses of water they drink. Water is also present in many foods. A person needs between 2 and 3 litres of water a day. Also ask the children whether they think that water consumption changes with the season, and if so, how and why.
4 What percentage of water is there in a cucumber?
98% water.
5 Why does the body need carbohydrates?
The body needs carbohydrates to provide energy.
6 Do you need energy at night when you are asleep? Explain why.
Yes, in order to breathe. All the systems of the body keep
working when you are sleeping. Energy is also needed while one is
asleep to maintain the body temperature.
7 What happens if you eat too little?
You become weak, and have little energy to do anything. This can also lead to illness, because the body cannot fight off attacks from germs.
8 What happens if you eat too much?
You become fat. People who work hard use up a lot of energy,
they can replace this by eating good food. Too much fat is bad for you.
B Tick the correct answer. Try to explain your choice:
1 Dietary fibre can be found in:
a milk b grapes c eggs d salt
The skins of grapes form the dietary fibre.
2 The system which uses the most water is:
a skeletal b digestive c nervous
The digestive system uses the most water.
3 This vitamin builds up teeth and bones:
a vitamin A b vitamin B c vitamin C d vitamin D
Vitamin C keeps teeth and bones healthy, but vitamin D is
needed to build healthy bones. Lack of vitamin D causes rickets.
4 This food is one of the best for a young person:
a salt b beans c mangoes d milk
Milk contains proteins, fats, vitamins and minerals.
Unit 7: Looking after yourself (pages 17-20)
Questions (page 20)
A1 What are some of the ways in which we can preserve food?
Food can be preserved by cooking or boiling, adding chemical preservatives, freezing and sealing it away from the air.
2 What does sterilization mean?
Sterilization means to make sterile. When we sterilize something we are making it free from germs.
3 How can flies cause you harm?
Flies pick up diseases from animals. These can be passed on to man. Flies eat off rubbish and open food. They pick up germs and transfer these to food that we may be eating. When germs enter the body we become ill.
4 What are the main kinds of germs which cause infections?
Viruses, bacteria, protozoa and fungi.
5 What is a parasite?
An organism that lives off healthy cells and multiplies.
6 What are some of the ways in which you can keep healthy?
See the list on page 18.
B Find these words in a dictionary. Write down what they mean.
a sterilize b germ c preserve d infection e disease
Part 2: Living things
Unit 8: Living things (pages 21-24)
Questions (page 24)
A1 What is one important thing that plants can do but animals cannot?
Make their own food.
2 Why do animals move from place to place?
They move in search of food and water. They also move in search of mates, and to escape from predators.
3 What is the lateral line on a fish? What does it do?
The lateral line is a line along the side of a fish. This line enables the fish to sense movements in water. The fish can tell by these movements whether there is food or danger nearby.
4 What is locomotion?
Locomotion is movement or motion from place to place.
5 What senses does a zebra use to tell if there is danger nearby?
The zebra uses its sight, hearing and smell.
B1 What are some of the different ways in which living things breathe?
A human breathes (or respires) through the nose; mammals breathe through the nose; fishes breathe through gills; an earthworm breathes through the skin; insects breathe through their trachea; plants take in air through the leaves.
2 Do you remember what the word migration means? What
happens when animals migrate?
Migration is the periodic movement of animals from one place to another. This movement is usually associated with seasonal climatic changes or breeding cycles. Migration is best known among birds.
Unit 9: Life cycles (pages 25-27)
Questions (page 27)
A1 What are the five main groups that vertebrates can be divided into?
Fish, amphibia, reptiles, birds, mammals.
2 Why is animal reproduction important?
If animals did not reproduce their species would come to an end.
3 What do these words mean? (Look in a dictionary if you are not sure).
Get the children to look up the meanings in a dictionary.
a extinct: (of family, class, species) that has died out
b reproduce: multiply by generation
c vertebrate: (of animals) having a spinal column
d fertilization: making fertile or productive. This occurs when a sperm, or male sex cell enters an egg, or female sex cell.
4 How are the young of birds and mammals able to survive?
They are looked after by the parent(s).
5 Why do you think an insect lays so many eggs?
Insects lay many eggs because the eggs and baby insects are usually defenseless. Many of them will not survive, but at least some will. In this way the species is sure of surviving.
6 How do micro-organisms usually reproduce?
By cell division.
B Look carefully at the life cycles shown on page 26. For each animal shown, describe what happens at each stage. Choose one of the animals and write and draw pictures to show what happens.
Animals which reproduce sexually begin life when an ovum from the female is fertilized by a sperm from the male. When the young of a species develops outside the mother’s body, they often have to pass through various stages of development. Young which hatch from an egg are called larvae. Insect larvae often take the form of grubs, maggots or caterpillars. Butterflies and moths pass through a pupal stage (forming a cocoon around themselves). Butterfly =
egg, caterpillar, pupa, adult.
Unit 10: Plant distribution (page 28-31)
Questions (page 31)
A Which of these statements are true? Rewrite those that are untrue.
1 Most simple plants produce seeds.
F…produce spores
2 Animals help to spread seeds
F
3 Plankton is found in water.
T
4 Liverworts grow from seeds
F…bits of the parent plant.
5 A puffball is a kind of algae.
F…of fungus
B1 What are some of the main ways in which spores are spread?
By water or wind action.
2 What are some of the main ways in which seeds are spread?
Wind, explosion, water, birds, animals (on fur and through deposits).
3 How are some plants adapted for survival? Can you think
of other ways in which plants adapt themselves?
They produce thousands of seeds. They grow thick leaves to retain moisture, some produce gums and resins to keep away insects, some have tough barks, some grow thorns and spikes, some produce poisons.
4 What experiments have you done to show that plants can only grow in certain conditions?
If the children have not done any experiments, you may do some now. Look in Books 2, 3 and 4. The experiments should show that plants need sunlight, water, good soil and air, in order to grow well.
Unit 11: Plant reproduction (pages 32-35)
Questions (page 35)
1 What is a bulb?
A bulb is a bud which is surrounded by thick swollen leaves, e.g. a tulip.
2 What are the two different ways in which plants can reproduce?
Sexually and asexually.
3 What is the female part of a flower called?
The carpel. The carpel contains a stigma, a style, the ovary and ovules.
4 What is the male part of a flower called?
The male part of a flower is called a stamen. (It consists of the anther and pollen grains, which contain the male sex cells).
5 How is the pollen from a flower transferred to the stigma of
another flower?
Mostly by insects or by wind.
6 What is a fruit?
Fruits are the ripened ovaries of flowers. They contain one or more seeds.
7 Why do you think flowers have bright colours, special
shapes and strong scents? (Think about this carefully).
These are used to attract bees, and other insects. By attracting insects the plant species is sure of survival.
8 In your own words try to describe how a flower is pollinated and fertilized.
Let the children write about it in their own way. When they have finished, check to see whether they have written it in a systematic way, illustrated what they have said with suitable diagrams, and have understood what they have written.
Unit 12: Crops (pages 36-39)
Questions (page 39)
A1 Which insects and other small creatures are pests? How do we protect crops from pests?
Weevil, sawfly, mite, aphid, beetles (of various kinds), slugs, chafer grubs, caterpillars, millipedes and woodlice are some pests. Rats, fieldmice and other larger insects such as locusts are also pests. We protect crops from such pests by spraying crops with insecticides. We also put down poisons to kill some pests.
2 What are some of the ways, that you can think of to protect crops? (First think of some of the ways in which they can be harmed, apart from harm by insects. Then think of how they can be protected).
By building ditches and putting up strong fences we can protect crops in the fields from animals. Some farmers put up scarecrows to scare away the birds. Some build little shelters above the ground and keep watch over their crops. Crops can also be covered (with polythene or sacking) to prevent birds from feeding off the crop, or to shield them against too much sunshine. Some farmers cover whole trees with nets to keep birds off. In some countries farmers grow crops in greenhouses; these protect the plants from frost, keep the warmth in, and also offer protection from birds and animals.
3 Young plants are looked after in a nursery. They are also provided with the best conditions. Can you say what these conditions might be?
Plenty of water, good soil with nutrients (manure and compost), sunshine.
4 Where was maize first grown? Does maize grow in Pakistan?
Maize was first grown in Central and South America. It grows in Pakistan.
5 What grains and cereals do you eat every day?
Get the children to find out for themselves.
B For each of the words below give the best explanation or
definition. Look in the text, as well as in a dictionary.
Brief explanations are given here. Let the children find out for themselves what these terms mean.
1 nomad: (member of a tribe) roaming from place to place for pasture.
2 pesticide: insect or pest killer.
3 fertilizer: a medicine or chemical that helps plants to grow better.
4 Manure: any substance spread over soil to fertilize it.
5 Settlement: a colony or group of houses where people live.
Part 3: Materials and matter
Unit 13: Useful measurements (pages 40-43)
Unit 14: What makes up matter (pages 44-49)
Questions (page 47)
A Look at these words.
atom theory molecule nucleus electron Which word goes with each of these descriptions?
a It consists of a single atom or several atoms grouped together. molecule
b It is the central part of an atom. nucleus
c It is tiny particle of matter which orbits the nucleus. electron
d It is a scientist’s idea for explaining something that has been discovered. theory
e It is a tiny particle of matter which rarely exists on its own.
atom
B1 What is a theory? What was the theory of the ancient Greek
philosophers about matter?
A theory is a scientist’s idea for explaining what has been discovered. The ancient Greek philosophers had a theory that all substances were made from earth, fire, air and water.
2 Give two properties for each of these: a solid, a liquid and a gas.
Solids have a fixed shape. They have a fixed volume. Liquids can change their shape. They cannot change their volume.
Gases have no fixed volume. They have no fixed shape.
(The answers may consists of other properties).
3 In which states can water exist?
Solid (ice), liquid (water), or gas (steam)
4 Explain why a) it is easy to pour a liquid, b) a gas will
completely fill any container, c) a solid expands when it is
heated.
a) It is easy to pour a liquid because in a liquid the molecules are not fixed in a particular pattern. The molecules move and slide about.
b) In a gas the molecules are far apart and the attraction between them is weak. The molecules are moving about all the time, and bouncing off in all directions. This is why a gas will completely fill any container.
c) When a solid is heated the atoms and molecules vibrate more strongly and therefore take up more space.
5 Why is it that a gas can be compressed into a smaller volume, but a solid cannot?
In a solid there is no space between the molecules. They cannot be pushed any closer together. In a gas there is lots of space between the molecules. They can be compressed.
Unit 15: Elements (pages 50-53)
Questions (page 52)
A1 Can you match these elements with the correct symbols?
Chlorine Copper (Cuprum)
Calcium Cobalt
Carbon Chromium
C1 Co
Ca Cu
C Cr
What do you notice about the symbols?
All the symbols begin with C. A second letter is used to differentiate one from the other. The second letter is usually (but not always) the second letter of the word. The symbol can be derived from the original Latin word (Cu).
2 Which of the following are not elements?
stone nitrogen gold plastic wood tin brass lead steel
(Those underlined are not elements).
B1 What is an element? Give three examples of elements.
An element is a simple substance which cannot be split into simpler substances. It contains one type of atom only. (There are many examples in the text).
2 Is brass an element? What is brass made of?
No. It is made of copper and zinc.
3 Your hair is made up of a combination of four elements.What are they?
Oxygen, hydrogen, carbon and nitrogen.
4 What does the symbol Fe stand for?
Iron.
5 What is a compound?
A compound is a substance which consists of different elements, chemically combined together.
Unit 16: Water (pages 54-57)
Questions (page 56)
1 Make a list of the properties of water. (You will have to
remember what you learnt last year!)
Water can exist in three states: when cooled (frozen) water changes from liquid to ice and its volume increases; ice is less dense than water (it floats); it is a solvent; it evaporates when heated; cooling condenses the water vapour in air to form water droplets; water contains air; water exerts pressure; etc.!
2 What action causes water to rise in some materials?
Capillary action (Check this by using absorbent paper or cloth dipped inwater.)
3 How does a siphon work?
See Introduction.
4 Why does water find its own level?
Like everything else water is pulled down by the force of gravity. Water always finds the lowest level it can possibly reach. (Get the children to test this. Look at the level of water in a glass. Tilt the glass. What happens to the surface? It remains parallel to the earth. Also do an experiment to show that two separate bodies of water can have different surface levels. When the two bodies are connected the water finds one level. This is how canals are built. Locks enable boats to travel along a canal which may drop many metres.)
5 Why is a raindrop a sphere?
Because the surface is held together by surface tension.
6 What is the ‘stretchy skin’ of water due to?
Surface tension.
7 Why do some objects float while others do not?
Objects which have a density which is lower than that of water can float. Objects that weigh less than the water they displace can float.
Part 4: Sky and space
Unit 17: The Sun and the Moon (page 58)
Questions (page 62)
A Some of these statements are not true. Find and correct
them.
1 The surface of the Sun is smooth.
(F)…not smooth.
2 The Sun produces Gamma rays and X-rays.
(T)
3 The two main gases in the Sun are helium and oxygen.
(F)…helium and hydrogen.
4 The Sun is about half way through its life.
(T)
5 The Sun is about thirty times as heavy as the Earth.
(F)…330,000 times as heavy.
6 Tides happen because of the Earth’s gravitational pull.
(F)…the Moon’s gravitational pull.
B1 What is the name of our galaxy?
The Milky Way.
2 What is the surface temperature of the Sun?
Approximately 6000 degree C.
3 What is a solar flare?
Sudden bursts or explosions on the surface of the Sun.
4 Which body has the weakest gravity, the Sun, Earth or Moon?
The Moon. (It is the smallest body of the three.)
5 How are tides caused? How often do they occur?
Tides are caused by the gravitational pull of the Moon. They occur approximately twice a day, (121/2 hours between one high tide and the next, with a low tide in between.)
6 Why is there no life on the Moon?
There is no air or water on the Moon. Living things need air and water to survive.
Unit 18: Space travel (pages 64-67)
Questions (page 66)
A1 What theories did people have about the Earth hundreds of years ago?
People thought the Earth was flat. They also thought that the Sun and other stars and planets revolved around the Earth.
2 Why are observatories usually built on high mountains?
The atmosphere is clearer and there is less pollution in the air. There may be less cloud cover.
3 How are balloons useful?
Balloons are used to find out about the middle layers of the atmosphere. They do not cost as much as aeroplanes or rockets.
4 Which was the first manned spaceflight?
The first manned space flight was the Russian spaceflight (Vostok I) in 1961. This took Yuri Gagarin into space.
5 Who was the first man to walk on the Moon?
Neil Armstrong.
6 What are satellites used for today?
They are used to tell us about the weather, to relay signals, to deal with communications, to help ships navigate at sea, and also to spy!
7 How are astronauts able to live on board a spacecraft?
Astronauts live and work in the command module. Inside the
spacecraft they have lifesupport systems. (This means that they have all the necessary things to keep them alive; oxygen, water, food, etc.)
B1 Try to write a brief description of each of the following:
a space module b astronaut
c weightlessness d life support systems
The children should use these headings to find out what they can from books and other sources. What they find out will depend on the books available and their interest and aptitude.
2 Why is a parachute no help to a spaceman landing on the moon?
Because there is no air on the moon to slow down the descent of the parachute.
Part 5: Earth and atmosphere
Unit 19: Changes in the atmosphere (pages 68-76)
Questions (page 74)
1 What is the study of the weather called? Meteorology.
2 What is the troposphere?
The layer of atmosphere closest to the Earth.
3 What is meant by precipitation?
Precipitation is when water vapour turns into droplets of rain, snow or ice, which then fall to the ground (precipitate).
4 How are clouds formed?
Clouds are formed when hot air rises, and the water vapour in the air condenses to form tiny droplets of water. These collect together to form clouds.
5 What is hail? How is it formed?
Hail is round particles of ice, which is formed in tall clouds called cumulonimbus clouds. The bottom of such clouds is warm, but the top can be freezing. Air currents in such clouds are strong, and these currents toss the drops of rain about. They freeze at the top and thaw when they come to the bottom of the clouds. When the droplets get bigger they fall out of the cloud as hail.
6 Which instruments are used to measure weather?
Wind vane, anemometer, thermometer, rain gauge, barometer, hygrometer.
Unit 20: Changes on Earth (pages 77-82)
Questions (page 81)
1 In your own words describe what kinds of rocks there are and how they are formed.
Igneous rocks: from hot, molten magma out of volcanoes. Sedimentary rocks: from layers of sediment. Metamorphic rocks: (metamorphosis means change) formed from existing rocks which have changed due to heat, pressure or chemical action.
2 How have fossils helped scientists?
They tell scientists about the shape of living creatures, now extinct, and help to date rocks. They also helped scientists to form theories about the continents.
3 How have the continents changes?
The continents at one time formed one land mass. Over millions of years they have drifted apart, and together, in various ways. This drift has caused changes in the coast lines and has given rise to mountains. The movement has also caused faults in the Earth’s crust.
4 What is a glacier?
A glacier is a large mass of moving ice, found high up in the mountains.
5 What is mechanical weathering?
When rocks crack, split or crumble due to changes in
temperature or pressure, mechanical weathering takes place.
6 What is a stalactite? How is it formed?
A stalactite is a deposit of lime (carbonate of lime) usually in the form of a large hanging from the roof of a cave, and formed by trickling water.
7 How has man changed the earth?
Man-made changes are occurring more frequently, especially as populations increase, and the building of dams, canals, the plantation of crops, deforestation, animal rearing, and collection of building materials (granite, sand, clay) are some of the reasons why the surface of the earth has changed.
Unit 21: Pollution (pages 83-87)
Questions (page 87)
A1 What is the environment?
Everything around you; the roads, the houses, the people, the air, nature.
2 Name at least five items which you waste or throw away at home.
The children can make up their own lists. These will probably
include, food (of various kinds), sweet wrappers, boxes (shoes,
toothpaste, biscuits, etc), old clothes, empty plastic and glass
containers (bottles, jars, tubes), tins and cans, half-used pencils, and many other things!
3 In your own words try to describe what acid rain is.
Coal is burned and smoke is produced. Fuel contains sulphur. When the sulphur combines with oxygen and water in the air, acids are formed, which fall to the earth as acid rain. Acid rain causes more pollution, destroys nature and causes diseases in humans and animals.
4 What wastes are produced in industry?
Most forms of energy also produce waste. Gases, chemicals, and other substances are wasted when these things are produced.
5 Why should we not use too many aerosols?
The spray propellant from aerosols mixes with the atmosphere and reaches the ozone layer. This gradually eats away the ozone layer, and enables harmful rays from the Sun to reach the Earth. These rays cause diseases in humans and animals, and abnormal growth conditions in plants.
B1 Which of the things shown below are biodegradable.
The biodegradable things are: rat, leaf, (some kinds of) paper, banana skin, dead tree trunk.
Part 6: Electricity and magnetism
Unit 22: Electricity (pages 88-93)
Questions (page 91)
1 What is a conductor? Can you give some examples good conductors?
Materials such as metals which allow electric current to pass through quite freely are called conductors. (Good conductors of electricity are also good conductors of hat.) Copper, iron, and aluminium are good conductors of electricity.
2 In your own words try to describe how current passes through a wire.
Allow the children to use their own words to describe this. The correct explanation is given on page 88/89 of the text. They might simply state that electric current is a flow of electrons through a cable or wire.
3 In what ways do we see electricity in nature?
In thunderstorms (lightning), in the body, in the electric eel. Static electricity can be experienced in many situations, for example, from doorknobs in air-conditioned hotel rooms!
4 What is a fuse? Why is it a useful component of a circuit?
A fuse is a short piece of thin wire which is connected to a circuit. It fuses (or melts) if there is too much current passing through the circuit, thus preventing damage to components or expensive equipment.
5 What is a resistor? Why are resistors needed?
A resistor ‘resists’ the flow of current. They are used to allow
different components to receive different voltages.
Unit 23: Electromagnets (pages 94-97)
Questions (page 97)
1 How does the buzzer make a buzzing sound?
When the current is switched on the electromagnet will work. It will attract the piece of tin. The rubber band will pull the piece of tin will make a buzzing noise as it virbates backwards and forwards.
2 If (A) is touching (G), and not touching (B), what happens when you switch on the current?
For your benefit, the question has been rewritten: If the piece of tin is touching the screw, and not touching the electromagnet, what happens when you switch on the current?
Answer: The electromagnet will pull the piece of tin towards it, and the rubber band will pull back.
3 If (B) is touching (A), and (G) is not touching (A), what happens when you switch on the current?
The question rewritten: If the electromagnet is touching the piece of tin, and the screw is not touching the tin, what happens when you switch on the current?
Answer: Nothing. The electromagnet will hold the piece of tin. The tension in the rubber band will have to be increased.
4 What use can you make of the buzzer? Could you use it as a burglar alarm?
If the switch is replaced by a pad of some kind it can be used as a burglar alarm. The burglar will have to complete the circuit in some way. This can either be done by connecting the two wires to two points close to each other on a sliding window, or placed under a doormat. This will have to be discussed with the children. Allow them to come up with solutions of their own. Will it work? Try out some of their idea.
5 Draw diagrams to show how you would use the buzzer to make:
a a burglar alarm
b a device to tell you when a tank is full
Again, ask for plans in writing and with illustrations.
Part 7: Machines, force and energy
Unit 24: Forces (pages 98-103)
Questions (page 102)
A1 What are some of the things that a force can do?
A force can change the way things move. A force can speed up motion, slow it down, change the direction of an object in motion, change the shape of an object. Equal and opposing forces can balance an object.
2 What forces are most likely to slow down an object travelling through the air?
The friction between the air and the object.
3 What force is exerted on you, when you push against a
brick wall?
An equal force in the opposite direction.
4 In what way can metal and wood be made to exert an elastic force?
Metal coiled into a spring can produce an elastic force. Press on the metal spring and it exerts an elastic force. A length of wood can also act like a spring in the same way, e.g. a diving board.
B1 Will these levers balance?
The coins in a are exerting equal turning forces about the pivot, but in opposite directions. The coins are at the same distance from the pivot. The single coin in b is exerting the
same turning force as the two other coins about the pivot,
but look at where they are placed!
In c, the single coin is exerting the same turning force as
four coins. They are even closer to the pivot. (Tape the ruler to the pencil, so that it balances. Place coins on the ruler, and do the experiment yourself.)
What does this experiment tell you about force?
What does the experiment tell you about levers (and pivots)?
Get the children to do these and similar exercises. If there is a seesaw in the playground get the children to see how that can be balanced in the same way, using themselves as weights. In order to balance a lever, an equal (or balancing) force must be exerted on each side of the pivot. It is important to know where this force has to be applied. The children should see that the force needed is least when it is further away from the pivot. In the following Unit they will be able to see how some machines with levers actually work.
Unit 25: Machines (pages 104-110)
Questions (page 108)
A1 What use are machines?
Machines help us to do work, machines can exert greater forces than we can.
2 How many classes of levers are there? Give an example of each.
Three.
1st class lever : pliers (fulcrum in middle).
2nd class lever : wheelbarrow (load/weight in middle).
3rd class lever : tweezers (effort/power in middle).
Note that a lever is a straight bar or other rigid structure of which one point (fulcrum) is fixed, another is connected with the force (weight or load) to be resisted or acted upon, and a third is connected with the force (power or effort) applied.
3 What use are inclined planes? Have you seen any in use?
Inclined planes are used as ramps to unload goods from the backs of lorries, for easy access of wheelchairs into buildings, for pleasure (slides), and for many other jobs.
4 How are pulleys useful?
Pulleys are used to lift heavy objects. (Cranes on building sites use levers and pulleys, heavy containers are loaded onto ships with pulleys; felled trees and buckets of water from wells are also lifted by pulleys.) Pulleys are also particularly useful for changing the direction of a force.
5 What is a screw used for?
A screw is used to hold things down. A screw can also be used to move a weight from one place to another (see a monkey-wrench or car jack).
6 What is a wedge? Give some examples.
A wedge is a piece of wood or metal with an angled (acute angled) edge. It is used to cut, split or widen an opening. It exerts force in various ways. Knives and axes are wedges.
7 In what ways are wheels useful?
Wheels are used in many machines with rotary movement, such as clocks, vehicles, engines and toys. Wheels are used to make things move forward; they can also be used to change direction.
B1 Make a list of all the things you can see which have screws in them.
Have the children noticed that screws have a slit in the head (to take the wedged end of a screwdriver) and that nails have flat heads? If they look at all the wooden furniture, windows, cupboards, watches or clocks, pencil boxes and other objects in the class room they will be able to find a number of screws.
2 Why is an oar a Class 2 lever?
Because the blade, not the rowlock, is really the fulcrum.
Note:
Watts Planetary Gear: This is a gear-wheel which goes round another gearwheel (roughly as the planet goes round the Sun). The gearwheel is moved backwards and forwards by a piston; it moves round the middle gearwheel (which is fixed o a big wheel) and so turns this gearwheel and the big wheel. A band joins the two wheels together.
3 What kind of levers do you think these are?
Get the children to make their own drawings and mark each lever with the letters F (fulcrum), E (effort), and L (load).
1st class: (fulcrum in middle) bat, scissors, forceps
2nd class: (load in middle) bottle opener, nutcracker.
3rd class: (effort in middle) arm, fishing rod, tongs.
Part 8: Sound, light and colour
Unit 26: Sounds (pages 111-114)
Questions (page 113)
1 In your own words try to describe how sounds are made and how they travel through the air.
Let the children use their own words, but make sure the ideas are correct. The information they can use is contained in the first two paragraphs of the Unit.
2 How do we measure the amplitude of sound? What does amplitude mean?
Amplitude means loudness. The amplitude of a sound wave refers to the height of each wave. This is measured in decibels (dB).
3 How do we measure wavelength?
Wavelength is measured in millimetres and metres. It is the distance between each wave of sound.
4 Do low sounds have a high frequency or a low frequency?
A low frequency.
5 In what conditions do echoes occur?
Echoes occur where there are no objects to absorb sound, but there are hard surfaces to reflect sound. In large empty rooms or in the mountains, sounds echo or bounce back.
6 How do bats find their way?
Bats make a high pitched squeaking noise. This sound bounces off objects and returns to the bat’s ears. Bats have sharp ears to hear these sounds.
7 In what ways do we control sounds in a city?
Cars have silencers to stop too much noise from coming out of engines. Buildings have thick walls and special sound-proofed windows. Near hospitals there are signs for motorists telling them not to blow their horns!
8 Why are pressure horns harmful?
They are so loud and sprill that they can burst one’s eardrums.
Unit 27: Light (pages 115-116)