Idea Transcript
Bo ok Th re e
Junior
Life processes
• Adaptation
• Separating mixtures
• Healthy living
•
Science Answer Book
Forces
• Sound
• Chemical changes
w w w.galorepark.co.uk
Sue Hunter and Jenny Macdonald
Junior Science Book 3 Answer Book
Sue Hunter and Jenny Macdonald Series Editor: Louise Martine
www.galorepark.co.uk
Published by Galore Park Publishing Ltd 19/21 Sayers Lane, Tenterden, Kent TN30 6BW www.galorepark.co.uk Text copyright © Sue Hunter and Jenny Macdonald 2011 Illustrations by Ian Moores and Rowan Barnes-Murphy D0125033 This document may be reproduced free of charge by the individual or for classroom use within the school or institution which purchases the accompanying textbook. Copies remain the copyright of the authors and such copies may not be distributed or used in any way outside the purchasing individual or institution. The textbook to accompany this answer book is available from Galore Park. Junior Science Book 3 ISBN 978 1 905735 32 7
Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi Chapter 1: Life processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Life processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Life story of a meerkat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Life story of an acacia tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 1 1 2
Chapter 2: Adaptation and evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Why are there so many different organisms? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 3 3 4
Chapter 3: Life cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Animal and plant life cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . All change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Our own life cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Making a baby . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7 7 7 8 8
Chapter 4: Healthy living . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A healthy, balanced diet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The heart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Breathing difficulties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Taking good care of the amazing human body machine . . . . . . . . . . . . . . . . . . . . . . . . . . .
10 10 10 11 11
Chapter 5: Microbes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Microbes and disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What can be done to help? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Edward Jenner and smallpox . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Not all bad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13 13 13 14 15
Chapter 6: Separating mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mixtures are all around us . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Separating mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . How we can use separation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Drawing science diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chromatography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16 16 16 17 18 19
Chapter 7: Chemical changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What is a chemical change? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . An important chemical change – combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . More about candles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Another chemical change – rusting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21 21 21 21 22
iv
Chapter 8: Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What is soil? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Something else is needed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Finding out more about soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Life in the soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23 23 23 24 25
Chapter 9: Hear the sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sounds are made when something vibrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sounds travel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Music to my ears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26 26 27 27
Chapter 10: More about forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 What is a force? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Spotting forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
v
Introduction Science is a subject that invites enquiry. The text in Junior Science Book 3 contains many interesting facts and opens the way for further research should a child feel inclined to find out more. Each chapter includes a number of exercises that are designed to focus the readers’ attention on what they have read, assess their understanding of the material and to encourage them to think more analytically about the topic. There are three types of exercise: cloze (‘fill in the gaps’) exercises, comprehension type questions and extension exercises requiring thought and application. All can be used in a number of ways depending on the ability of the pupils and the requirements of a lesson. The extension exercises, for example, could be used by teachers as stimuli for discussion, homework activities, opportunities for further development for quick workers etc. The answers given here should be seen as a guide. We do not expect every child to reproduce our answers exactly and each child should be encouraged to respond to the best of their ability. For some, success will be achieved if they can correctly extract basic information from the text. Others can be encouraged to look for more than the most basic answer by reading the text more critically. Those with the ability and interest can be encouraged to find out more and expand their knowledge through further reading or to think more deeply about the implications and applications of the material offered. Sue Hunter and Jenny Macdonald March 2011
vi
Chapter 1: Life processes Life processes Exercise 1.1 1. 2. 3. 4. 5. 6.
seven alive energy oxygen nutrition reproduce
Exercise 1.2 1.
The seven life processes are movement, reproduction, sensitivity, nutrition, excretion, respiration and growth.
2.
Plants make their own food but animals have to take their food from their surroundings.
3.
We sense our surroundings using eyes for seeing, ears for hearing, nose for smelling, mouth (tongue) for tasting and skin for feeling.
4.
Reproduction is the process of making more individuals of a particular species to prevent the species becoming extinct.
5.
Most living things need to take oxygen from the air to release energy from their food in the process called respiration.
Life story of a meerkat Exercise 1.3 1. 2. 3. 4. 5. 6.
milk grows, beetles, larvae, geckos three older, younger (in that order) one alarm, run
Exercise 1.4 Extension questions 1.
A meerkat that is on duty will need to use its senses to spot dangers and alert the group. It needs to be able to see clearly over long distances and hear or smell an approaching predator. Other meerkats need good hearing to hear and respond quickly to the alarm call. Pupils may also find out that there are different alarm calls for different types of danger, e.g. birds of prey or snakes. The troop will react differently depending on the nature of the danger. 1
2.
Meerkats help each other by grooming and working together to find food. Older meerkats help mothers bring up the younger ones by helping to teach them about how to find food. Pupils may also find out that when the group goes hunting, adults take turns in staying by the burrow to look after youngsters that are too young to travel with the group.
Life story of an acacia tree Exercise 1.5 1. 2. 3. 4. 5. 6.
leaves, light taste, ants thorns beetles elephants grow
Exercise 1.6 1.
The ants protect the tree from browsing animals by stinging their noses.
2.
(a) The elephants eat the pods but do not chew up all the seeds. The seeds survive the journey though the elephant’s gut but the beetle grubs in the seeds are killed. The seeds are then deposited at some distance from the parent tree in the elephant’s dung. They can then grow into new trees without competition from the parent plant. (b) The elephants help the tree carry out the process of reproduction. (c) The tree helps the elephant carry out the process of nutrition.
3.
Insects help the tree carry out reproduction by pollinating the flowers. Some insects also help by protecting the tree from animals that might eat the seed pods.
Exercise 1.7: Extension question The answer should include details of how the chosen organism carries out the life processes in its habitat, especially nutrition, movement, reproduction and growth.
2
Chapter 2:Adaptation and evolution Keys Exercise 2.1 1.
(a) earwig (b) ground beetle (c) harvestman (d) mite
2.
Any suitable question based on observable characteristics, e.g. Does the animal have legs that stick out from its body?
3.
(a) fallow deer (b) fox (c) badger (d) pony (e) sheep (f) pet cat
Exercise 2.2: Extension question The key should contain questions based on observable characteristics such as hair colour, eye colour, etc. rather than non-observable traits such as ‘smiley’ or ‘good at music’. Questions should not be based on things that can change, such as items of clothing.
Why are there so many different organisms? Exercise 2.3 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
adaptations predators dustbins any three of: rabbits, pheasants, chickens, fruit two lemmings ears leaves, light spines, eaten water store
3
Exercise 2.4 1.
(a) All the foxes have fur, forward-facing eyes, pointed ears and long tails. They have similar shaped heads. They are all predators and all have a varied diet. They have good eyesight and hearing. (b) The red fox has reddish brown fur that stays the same colour all year but the fur of the arctic fox is white in winter and greyish brown in summer. Arctic foxes have special two-layered fur to keep them warm but the red fox has thinner fur. The Arctic fox has other adaptations not needed by the red fox, e.g. fur on the underside of its feet and extra blood vessels in its feet. The ears of the Arctic fox are smaller than those of the red fox and its tail is bushier and its legs are shorter. (c) The fur of the fennec fox is too thin to keep it warm in the cold Arctic weather. It would lose too much heat through its huge ears and it is too small to hunt lemmings and other Arctic prey.
2.
(a) Bluebells flower early so that they can absorb enough light from the Sun to complete their reproduction before the leaves on the trees above open fully and create shade on the woodland floor. (b) Late frosts might damage the flowers, and the cool weather means there may not be very many insects around for pollination. (c) The bluebell’s leaves and stem die back and the plant survives underground in the form of a bulb. The bulb is full of stored food made by the plant before the leaves died down.
3.
Cactus leaves have changed to become spines. These prevent animals from eating the plant. The stem is big and green and carries out photosynthesis to make food for the plant. Water is stored in the big, thick stem, which has a thick, waxy, waterproof layer to prevent water from evaporating.
Evolution Exercise 2.5 1.
At first people thought fossils were patterns in the rocks that just happened to look like animals. Others thought they were the remains of animals and plants that had been killed in the great flood.
2.
Evolution is a slow change in animals and plants over long periods of time. (This sometimes leads to the creation of new species.)
3.
(a) Darwin sailed in HMS Beagle. (b) The captain of the ship was Captain Fitzroy. (c) Darwin was Fitzroy’s assistant and provided him with company on the long journey. He spent the journey studying the geology, plants, animals and people in the places they visited.
4
4.
The islands where Darwin observed giant tortoises and finches are the Galapagos Islands.
5.
Darwin noticed that, although the animals on all the islands were similar, each island had slightly different versions.
6.
(a) Darwin suggested that some animals are born with natural differences from their parents. Some of these differences make the offspring better able to survive and reproduce and so their characteristics would become more common in the next generation. He suggested that over many generations this could lead to the development of new species. (b) He called the process ‘natural selection’.
7.
People were not happy about Darwin’s theories because they made people question the creation story in the Bible. They were also unhappy to be told that they might be descended from monkeys.
8.
Scientists are finding more information about how evolution occurs from new fossils that have been found and also from the study of genes.
Exercise 2.6: Extension question Darwin visited the Canary Islands, Cape Verde Islands, Rio de Janeiro, Falkland Islands, Galapagos Islands, New Zealand, Sydney, Tasmania, Mauritius, Cape Town, St Helena and Ascension Island. A map of the route is included on the next page.
5
Galapagos Islands
6
Falkland Islands
Rio de Janeiro
Cape Verde Islands
St Helena
Ascension Island
Canary Islands
Cape Town
Portsmouth
Mauritius
New Zealand Tasmania
Sydney
The route taken by HMS Beagle when Charles Darwin was on board.
Chapter 3: Life cycles Animal and plant life cycles Exercise 3.1 1. 2. 3. 4. 5. 6. 7.
reproduce, extinct cell, splitting two sperm egg, ovum gametes gametes, fertilisation, zygote
All change Exercise 3.2 1. 2. 3. 4. 5.
metamorphosis nettle tents pupa pupa, imago (in that order)
Exercise 3.3 1.
Metamorphosis is a change of body shape that occurs during the life cycle of some animals such as butterflies and amphibians.
2.
Frogs and (Red Admiral) butterflies undergo metamorphosis as do many other insects, e.g. flies and beetles, and amphibians, e.g. toads and newts.
3.
Red Admiral caterpillars feed on nettles.
4.
A Red Admiral pupa is found inside a tent of nettle leaves and is greyish brown with a hard skin.
5.
In the pupa the caterpillar-shaped body becomes a three-part insect body (head, thorax and abdomen) with three pairs of legs and two pairs of wings.
6.
The skin of the pupa splits open and the insect pulls itself out onto the plant. It pumps blood into its wings to stretch them out and it will sit in the sun for a while to dry them before flying off.
7.
Frogs are amphibians.
8.
Frogs lay their eggs in the water in a pond, usually the pond where they were born.
9.
Frogs’ eggs are called frog spawn.
7
10. Tadpoles live only in water. They have tails and no legs. At first they breathe through external gills and eat plant material. Later they develop internal gills and they eat small animals. Frogs have no tails and they have two pairs of legs. They have webbed feet for swimming. They have lungs to breathe air but can also absorb oxygen from the water through their skin. They eat insects, which they catch with a long, sticky tongue.
Exercise 3.4 1.
(a) If there are thousands of eggs in the same pond, each one has a better chance of surviving because there are so many others that might be eaten by predators. (b) If there are many tadpoles in the same pond, they will all be competing for the same food and living space.
2.
Many rainforest frogs lay their eggs in pools of water that collect in the centre of epiphytic plants growing on the branches of trees and in shallow depressions in the branches.
Our own life cycle Exercise 3.5 1.
A human baby needs to learn to feed, recognise its parents, communicate with its parents to tell them if it is hungry, tired or uncomfortable. It needs to learn how to make sense of the images of the world which it sees when looking around and the sounds it hears.
2.
The time when a human changes from a child to an adult is called puberty.
3.
During puberty, a boy’s voice ‘breaks’ and the penis becomes larger.
4.
A woman’s breasts produce milk for her babies.
5.
When a girl has a period, the thick lining of the womb breaks away and leaves the body through the vagina. This lasts for a few days each month. The womb will then develop a fresh lining.
6.
Both boys and girls may find that their skin becomes greasier, that their bodies smell differently and that they grow thicker hair in certain places on their bodies. They may also find that they become moody and that they care a lot more about what other people think of them.
Making a baby Exercise 3.6 1.
(a) Eggs are produced in the woman’s ovaries. (b) One egg is normally released from one ovary each month. (c) The tubes linking the ovaries to the womb (uterus) are called fallopian tubes or oviducts.
2.
Each month a fresh lining is made in the womb. This contains lots of tiny blood vessels.
8
3.
(a) If no fertilised egg reaches the womb, the thick lining is lost, causing a period, and a fresh lining is made. (b) This process is called the menstrual cycle.
4.
Sperm are produced in the man’s testes.
5.
The man and woman get very close together. The man pushes his penis into the woman’s vagina and the sperm are released into the vagina through the man’s urethra.
6.
Fertilisation takes place in the fallopian tube (oviduct).
7.
The developing baby in the womb is called a fetus.
8.
The baby is connected to the mother by the umbilical cord and the placenta. The baby’s blood flows through the umbilical cord to the placenta and back again. The placenta is joined to the lining of the womb where there are lots of little blood vessels containing the mother’s blood. Oxygen and nutrients from the mother’s blood can pass into the baby’s blood and be carried to the baby.
9.
The fetus is protected from injury inside a bag of fluid called the amniotic sac.
10. A human baby takes nine months to develop in the womb.
9
Chapter 4: Healthy living A healthy, balanced diet Exercise 4.1 1. 2. 3. 4. 5. 6.
nutrients carbohydrates, fats proteins vitamins, minerals balanced pyramid
Exercise 4.2 1.
Food labels are important because they tell us what is in the food. This allows us to choose a healthy diet and also allows people with special diets or food allergies to know which foods to avoid.
2.
The traffic light colours on food labels are a quick way of seeing whether or not the food is a healthy choice.
3.
The information for a portion tells us how much of each nutrient we would eat in one portion of the food. The values for 100 g allow us to compare different foods accurately.
Exercise 4.3: Extension question 1.
Oven chips have been prepared in a factory and have other ingredients added to them so they are not just potatoes. Loose potatoes are a single food without any added ingredients.
2.
Loose carrots might be chosen because they are healthy, fresh vegetables. Frozen and tinned carrots can be stored and are quick and easy to prepare. Tinned carrots would be a better choice when there is no electricity for storage, for example when camping.
The heart Exercise 4.4 1. 2. 3. 4. 5. 6.
heart, blood arteries, veins, capillaries arteries veins carbon dioxide, oxygen (in that order) oxygen
10
7. 8. 9.
waste valves exercise
Breathing difficulties Exercise 4.5 1.
When you exercise, your muscles are using up energy faster than when you are sitting. Muscles need glucose and oxygen to obtain energy. To take glucose and oxygen to the muscles more quickly, the blood needs to flow faster so the heart rate increases.
2.
The blood enters the heart from the body. It moves through the heart and is pumped out from the heart to the lungs. From the lungs it returns to the heart and is then pumped out again to travel round the body before returning to the heart again.
3.
Smoke contains substances that irritate the surface of the lungs and this makes the lungs produce more mucus and may also cause swelling in the tubes in the lungs. This makes it harder to breathe. Tar may also coat the surface of the lungs, making it harder for oxygen to pass into the blood. Smokers therefore find it harder to get oxygen into the blood so the muscle cells cannot release enough energy from the glucose for exercise.
Taking good care of the amazing human body machine Exercise 4.6 1.
Smoking may cause lung cancer and other lung diseases, such as emphysema. It can also cause heart disease and increase the risk of a heart attack.
2.
If a substance is addictive, people who take it into their bodies find it hard to stop and always want more.
3.
The addictive chemical in tobacco smoke is called nicotine.
4.
Alcohol slows down people’s reaction times and may also affect their judgement and make them take unnecessary risks. This means that they are not safe to drive a car.
5.
The liver removes alcohol from the body.
6.
People who drink a lot of alcohol may become violent and become involved in fights. They may lose their sense of balance and fall over easily and they may be sick.
7.
A medicine is a drug that is usually prescribed by a doctor to prevent illness or help someone to recover from illness.
8.
The dose of a medicine is carefully calculated for the person for whom it is prescribed. If it is taken in the wrong dose it may not be safe.
9.
Syringes that have been used may have harmful chemicals in them or disease-causing microbes on them so they should only be handled by someone who knows how to do so safely.
11
Exercise 4.7 Extension question The story should demonstrate that the writer understands that peer pressure can influence young people and suggest at least one way in which someone can stand up to the pressure or get help.
12
Chapter 5: Microbes Microbes and disease Exercise 5.1 1. 2. 3. 4. 5. 6.
small, microscope harmful, helpful bacteria, fungi, viruses bacteria colds, flu drinking water, air, touch
Exercise 5.2 1.
A microbe is a living thing that cannot be seen with the naked eye.
2.
Microbes are also known as micro-organisms.
3.
The three main groups of microbe are bacteria, viruses and fungi.
4.
Bacteria cause diseases such as sore throats, whooping cough, bronchitis, food poisoning, typhoid and cholera. (Three examples required.)
5.
Diseases caused by viruses include colds, flu, measles, chicken pox, smallpox and HIV/AIDS. (Three examples required.)
6.
Sneezing and coughing blows microbial particles into the air and they can then be breathed in by other people. Microbes can be passed from one person to another by touch, for instance if someone does not wash their hands after using the toilet or sneezes or coughs into their hands and then touches something or someone else. Diseases such as cholera can be spread in drinking water and some diseases are spread by animals such as flies.
7.
(a) John Snow was the doctor who proved that cholera is spread in drinking water. (b) He persuaded the authorities to take the handle off a pump that seemed to be at the centre of the outbreak of cholera. This stopped people from drinking water from that well and the number of cases dropped rapidly.
8.
Robert Koch was the German scientist who showed that cholera is caused by a bacterium.
What can be done to help? Exercise 5.3 1.
It is important to wash your hands before a meal in order to remove the microbes and stop them from entering your body through your mouth.
2.
You should also wash your hands after using the toilet, handling animals or playing outside. 13
3.
You should put your hand across your mouth when coughing to reduce the number of viral particles being blown into the air. You should use a tissue when sneezing or blowing your nose and throw the tissue in the bin. You should also wash your hands more often than usual.
4.
(a) The medicines that can be used to cure diseases caused by bacteria are called antibiotics. (b) Alexander Fleming was studying bacteria and was a little careless about cleaning his apparatus. One day he found that a mould was growing in one of his dishes and seemed to be killing the bacteria. Howard Florey, Ernst Chain and Norman Heatley then developed a medicine from this mould. (c) Antibiotics are not given to people with colds or flu because they do not kill viruses.
5.
Another name for vaccination is inoculation.
6.
Vaccination involves injecting a small number of the virus particles that cause the disease, or dead virus particles, into the body. These encourage the body to produce antibodies, which are special cells that fight the disease. If you are then infected with the disease later, the antibodies are already there to fight the virus and stop you from becoming ill.
Edward Jenner and smallpox Exercise 5.4 1. 2. 3. 4. 5. 6. 7. 8.
Gloucestershire smallpox milkmaids, cowpox James smallpox children vaccination extinct
Exercise 5.5 Pupils should consider how the main characters in the story would feel and what they would be thinking. A class discussion is useful as a starter to this activity. This can also be approached as a group drama activity with groups writing and performing short plays.
14
Not all bad Exercise 5.6 1.
Foods that are made using microbes include bread, cheese, yoghurt and chocolate.
2.
Decomposers break down dead plant and animal material, clearing it away from the environment and returning valuable nutrients to the soil.
3.
Microbes in the gut help with the digestion of food, produce useful vitamins and help to keep the immune system healthy. They also help to fight harmful bacteria that might cause disease.
4.
(a) Yeast is added to dough to make bread rise. (b) The yeast respires, feeding on sugars in the dough. The carbon dioxide produced becomes trapped in the stretchy dough, forming bubbles which make the dough rise.
5.
Bread made without yeast is called unleavened bread.
6.
Fermentation is the action of yeast on the juices from fruit or grains during the production of wine and beer. The yeast feeds on the sugars and turns them into alcohol.
7.
Wine is made by adding yeast to water and fruit juice, usually from grapes.
8.
People in medieval time drank wine or beer rather than water because the water was not treated as it is today and contained disease-causing microbes. Fermentation kills off the microbes, meaning that the wine and beer was safer to drink than water.
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Chapter 6: Separating mixtures Mixtures are all around us Exercise 6.1 1. 2. 3. 4. 5.
mixture gases nitrogen, oxygen (in that order) sodium pure
Exercise 6.2 1.
Sea water contains dissolved salts, sodium chloride and other plankton and possibly plant material (sea weed), silt, sand, shell particles, chemicals from factories or from farmland or sewage. (Allow other valid suggestions.)
2.
You could evaporate the water from a sample of sea water and a sample of tap water. The sea water would leave a larger deposit than the tap water.
3.
The Dead Sea is between Israel and Jordan.
4.
It is easy to float in the Dead Sea because it is about eight times more salty than ordinary sea water. (This increases its density so that the difference between the density of the water and of the human body is increased, making the body more buoyant.)
5.
The Dead Sea is the lowest place on earth. It is over 400 metres below sea level.
Separating mixtures Exercise 6.3 1.
The solvent is the liquid part of a solution.
2.
In a solution of salt in water, the salt is the solute.
3.
A suspension is formed by tiny pieces of an insoluble solid floating in a liquid, giving it an opaque or milky appearance.
4.
(a) Water and gravel could be separated by decanting or sieving. (b) A solution of salt in water can be separated by evaporation. (c) A suspension of powdered chalk in water can be separated by filtering.
5.
The particles of the salts dissolved in sea water are small enough to pass through the holes in the filter paper.
6.
If you heat a solution until it is completely dry, hot pieces of the solid may spit out or you might overheat the solid which might cause a change in the substance.
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7.
The soil particles or silt are insoluble so they would remain in the filter paper to become the residue.
How we can use separation Exercise 6.4 1. 2. 3. 4. 5.
preserve, meat timber, glass sea, mines sea, millions plastics, petrol
Exercise 6.5 1.
Salt was valuable because it is essential in people’s diet; it was used for preserving food; and not every country has salt deposits so it could be used to trade for other products.
2.
(a) In hot countries, water can be evaporated from sea water in shallow lagoons using the heat from the Sun. (b) In Britain, sea salt is obtained by filtering the sea water and then heating it until the water boils away.
3.
The layers of salt were formed millions of years ago. The land was covered by a tropical sea which dried up, leaving a thick layer of salt behind. This then became covered by layers of sediment, and compressed into rock.
4.
Oil was formed from the bodies of tiny sea creatures which died and then sank to the bottom of the sea. They were then covered by layers of sediment and the pressure and heat caused the chemicals that made up the sea creatures to change into the chemicals that make up oil.
5.
Some products obtained from oil are: tar, petrol, diesel, aviation fuel, candle wax, lubricating oil, plastics, paint and fibres for clothing.
6.
The process used to separate the chemicals in oil is called fractional distillation.
7.
Alternatives to oil are needed because we are using up the oil reserves quickly and they will soon begin to run out.
8.
Bio-fuel is an alternative to petrol and diesel, and is made from plant material.
9.
Sustainable means that the product is made from a resource that is replaceable and does not harm the environment or threaten our well-being.
10. We must be able to grow plants needed to make bio-fuel without cutting down forests or using land that is needed to grow food.
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Exercise 6.6 Extension questions 1.
2.
Material
Is it soluble?
Are the pieces Is it magnetic? larger than 2mm?
Does it float on water?
wax pellets
no
yes
no
yes
powdered charcoal
no
no
no
no
salt
yes
no
no
no
iron filings
no
no
yes
no
G
Use the magnet to remove the iron filings.
G
Pour the remaining mixture into a sieve and shake to remove the wax pellets.
G
Add water to the remaining mixture and stir to dissolve the salt.
G
Filter to separate the charcoal powder from the salt solution.
G
Heat the solution to obtain the salt.
Allow workable alternatives. There are disadvantages to all possible methods and it is useful to discuss what these might be and how they could be overcome.
Drawing science diagrams Exercise 6.7 All diagrams drawn for this exercise should be drawn using a sharp pencil and a ruler. The labels should not clutter the diagram and the labelling lines should be ruled neatly in pencil. 1.
(a)
(b)
(c)
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2.
As above but should be drawn from memory.
3. residue
residue
or
filtrate
filtrate
Chromatography Exercise 6.8 1.
Chromatography is the process used to separate a mixture of soluble chemicals, e.g. the pigments in ink.
2.
Chromatography might be used by an art historian to compare the pigments in the paints from two or more pictures. It could also be used by the police to compare inks or other samples when investigating a crime.
3.
A chromatogram is the result of chromatography, usually a piece of paper on which the pigments have been separated.
4.
The most soluble dyes move the furthest so they will be at the top of the chromatogram.
5.
If a dye does not move at all, it is insoluble in water (or other solvent being used).
6.
The diagram should be drawn using a sharp pencil and ruler. chromatography paper
beaker inks being compared start line water
7.
(a) The children used five pens. (b) There are three different yellows. Those in pens A and D are the same pigment because they have travelled the same distance up the paper. Those in pens C and E are different because they have travelled different distances. 19
(c) There is only one blue dye. It has travelled the same distance in all five pens. (d) Pen B was made using only one dye. (e) Pens A and D might have been made by the same manufacturer because they have both split into pigments that are at the same heights on the chromatogram.
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Chapter 7: Chemical changes What is a chemical change? Exercise 7.1 1. 2. 3. 4. 5.
reversible non-reversible non-reversible reversible reversible
An important chemical change – combustion Exercise 7.2 1. 2. 3. 4. 5. 6.
combustion heat, fuel, air supply coal, oil, gas fire extinguisher, air supply electrical, fat (or oil) carbon dioxide, heavier
More about candles Exercise 7.3 1.
A candle goes out if it is covered with a jar because it uses up oxygen and eventually there is no longer enough oxygen to keep it burning. (Note: The candle does not use up all the oxygen. Combustion will only occur if there is at least 8–10% oxygen in the air. The candle goes out when this level is reached.)
2.
The main gases in air are nitrogen (roughly 78%) and oxygen (roughly 21%). The next most abundant gas in air is argon. Very small amounts of carbon dioxide (about 0.03%) are present. Other gases, such as neon and helium are present in tiny proportions.
3.
Nitrogen makes up over three-quarters of the air.
4.
Oxygen is needed for combustion.
5.
The products of burning a fuel in air are water vapour and carbon dioxide. (Also soot and carbon monoxide if there is a limited air supply.)
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Exercise 7.4: Extension question Weigh the candle and then burn it for a while, making sure that all the melted wax is collected. Then weigh the remaining candle, including the melted wax that has dripped down the sides. The mass of the remaining candle will be lower than the original, showing that not all the wax is still present.
Another chemical change – rusting Exercise 7.5 1.
Oxygen (air) and water are needed for iron to rust. (Other factors, such as the presence of salt or acid and temperature may affect the rate of rusting.)
2.
Dissolved air can be removed from water by boiling the water.
3.
A layer of oil floated on the surface of the water stops more air from entering the water.
4.
Silica gel (or anhydrous calcium chloride) can be used to absorb water vapour from the air.
5.
Steel objects rust because the main component of steel is iron, and iron is the only metal that rusts.
6.
When iron or steel rusts, the new product formed is crumbly and is not as strong as the original metal. This could make the car unsafe.
7.
(a) The chain of a bicycle moves round and rubs against the cogs on the wheel and pedals. This would cause paint to chip or wear away. Paint could also clog up the chain and make it less flexible, preventing it from moving smoothly. (b) The chain is usually kept rust free by covering it in oil to stop water and air reaching the metal.
8.
(a) Galvanisation means covering the surface of the iron or steel in a thin layer of another metal that does not rust, usually zinc. (b) The metal is first cleaned by dipping it into a tank of acid to remove the dirt and any rust on the surface. It is then dipped into a tank of molten zinc and removed. The zinc sticks to the surface of the metal in a very thin layer.
Exercise 7.6 Extension question Suggestions for keeping the sculpture shiny might include: varnish, oil, galvanising, wax polish, regular drying/polishing. Several methods should be suggested. These could be tested by treating pieces of the metal in each of the suggested ways and then leaving them outside for a time before comparing the results. The suggestion should include a reference to a control (a piece of untreated metal) to compare with the other results. The tests could be speeded up by placing the pieces in a container with water and air, e.g. placing them on damp paper towel or cotton wool in a box or bag.
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Chapter 8: Soils What is soil? Exercise 8.1 1. 2. 3. 4. 5.
minerals colour, texture rain, wind, temperature weathering gritty
Exercise 8.2 1.
Water gets into tiny cracks in the rock. When water freezes, it expands, pushing the cracks apart and making them bigger. Eventually the rock may break apart.
2.
Pictures should show the boulder rolling down the mountainside, maybe breaking up as it goes, falling into a river and being tumbled around and breaking up as it bumps into other rocks, eventually being deposited as small grains in the sea. The pictures should be clearly labelled or captioned.
Something else is needed Exercise 8.3 1.
Once-living things that may become part of the soil include leaves, branches or twigs, flowers, fruits, dead invertebrates and the remains of animals’ meals, e.g. worm pellets.
2.
The part of the soil made from dead plant and animal remains is called humus.
3.
Humus provides nutrients for growing plants and holds moisture in the soil.
4.
All the living things in the soil need air to survive. This includes the small animals, microbes and roots of plants.
5.
Clay particles are much smaller than sand particles.
6.
A sandy soil will allow water to drain more quickly than a clay soil because the spaces between the grains are larger.
7.
Fertile means containing lots of nutrients to support plant growth.
8.
Loam is a soil that contains a range of different particle sizes and plenty of humus.
9.
Gardeners and farmers like loamy soil because it is fertile and has a good structure allowing plants to grow well.
10. The materials in a compost heap are broken down by decomposers to create a crumbly mixture that can be added to the soil to increase the amount of humus and improve fertility. 23
Finding out more about soils Exercise 8.4 1.
(a) Sample 2 contains more gravel. (b) Sample 1 contains less clay. (c) Sample 1 might be described as loam because it contains sand, clay and plenty of humus.
2.
(a) 150 g (b) 40 g (c) Soil B could be described as a clay soil because it has lots of particles in the smallest bottom two trays, i.e. the smallest particles. (d) Soil A would allow water to pass through more quickly because it contains more of the larger particles and therefore would have larger spaces between particles. (e) Bar chart to show the particle size distribution in two soils 90 80
Soil A Soil B
Mass in the layer, in grams
70 60 50 40 30 20 10 0
3.
Top
Middle Lower Sieve layer
Bottom
(a) The farmer should look carefully at the particles in the soil. A well-drained soil will have large, gritty, sandy particles rather than sticky clay particles. (b) He could put equal depths of the soil samples into funnels, pour water steadily into the funnels and measure how much water passes through the soil samples in one minute. The soil with the best drainage will allow the most water to pass through. Alternatively, he could dig a hole in each field, making sure that they were the same size and depth, and pour the same volume of water into each hole and see how quickly 24
the water soaks into the soil. The best-drained soil will be the one where the water soaks in the most quickly.
Life in the soil Exercise 8.5 1. 2. 3. 4. 5.
micro-organisms invertebrates earthworms, moles air, water, roots leaves, humus
Exercise 8.6: Extension questions 1.
Earthworms move upwards in wet weather so they can come to the surface easily if their burrows are filled with water. If this happens, there will be no air for the worms to breathe and they will drown. They move downwards in hot, dry weather because they have to keep their skin moist so they can absorb oxygen.
2.
Since worms make wormcasts at the top of their burrows, it is possible to obtain a rough estimate of the number of worms in the lawn by counting the wormcasts. Note: If the lawn is big, the best method is to count the number in a square metre (or, better still, find the average number per square metre by counting in several square metre samples). The area of the whole lawn then needs to be calculated and the number per square metre is then multiplied by the area.
3.
The story should be based on the information given in the chapter rather than being completely fictitious. A believable story, based on scientific knowledge, with the minimum of anthropomorphism is the aim!
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Chapter 9: Hear the sound Sounds are made when something vibrates Exercise 9.1 1. 2. 3. 4. 5. 6. 7. 8.
vibrations backwards, forwards ears see cannot eardrum three two, sound
Exercise 9.2 1.
The bell vibrates. This causes the air to vibrate and the sound passes through the air to our ears where it makes the eardrum vibrate. This makes the three little bones in the middle ear vibrate and they pass the vibrations on to the cochlea. The cochlea turns the vibrations into electrical signals that are sent to the brain.
2.
The outer part of the ear channels sounds into the ear canal.
3.
If we had only one ear it would be harder to detect where a sound was coming from. This could be a problem when crossing roads (because it would be hard to hear where approaching traffic was coming from) and at play or in sport (when it would be hard to tell where someone was calling from). (Other suitable suggestions should be allowed.)
4.
Foxes prick up their ears and move their heads slightly from side to side to pinpoint the exact location of a sound coming from an animal moving through thick grass or undergrowth.
Exercise 9.3: Extension G
Communication through speech – sign language or lip reading can help.
G
Telephone conversations – use internet chat facilities or video phones.
G
Alarm clocks – have a flashing light and/or vibrating mechanism.
G
Films, theatre and television – use subtitles or surtitles to provide the dialogue in readable form.
G
Other suitable suggestions should be allowed.
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Sounds travel Exercise 9.4 1. 2. 3. 4. 5. 6.
solids, liquids, gases, vacuum (vacuum must be last) hard fifteen four silent see, hear, light, sound (in that order)
Music to my ears Exercise 9.5 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
vibrates pitch pitched longer, thicker air lower tighter, higher volume harder softer
Exercise 9.6 1.
Vibrating air
Vibrating strings
Vibrating reed
Vibrating skin
Vibrating wood or metal block
Vibrating lips
flute
violin
oboe
snare drum
xylophone
trumpet
piccolo
cello
clarinet
tympani
glockenspiel
horn
organ
double bass
bassoon
side drum
castanets
tuba
recorder
guitar
saxophone
bass drum
cymbal
euphonium
harp
bagpipes
tambourine
piano
cornet
tomtom
steel drum
bugle
gong
trombone
Other instruments can be added to these lists, including native instruments from other parts of the world.
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2.
Lower notes are made on the recorder when more of the holes are covered. This creates a longer column of air inside the instrument. Long columns of air make lower notes than short ones.
3.
A high note on the violin is made by fast vibrations. These are made because the string is short, thin and tight and is on a relatively small instrument. The low note on the double bass is made by slow vibrations. This is because the strings are longer and thicker that those on the violin and the instrument is much larger.
4.
When a drummer hits the drum hard, large vibrations are made in the skin so the sound is loud. To make a softer sound, the skin is hit more gently, making smaller vibrations.
Exercise 9.7: Extension question The strings are attached to the pegs at the end of the fingerboard. By turning the pegs, the strings can be tightened or loosened to change the pitch of the note created when the string is plucked. Standard tuning for guitar strings is E, A, D, G, B, E.
To help to get the pitch right, you could use a piano to play the right notes and then tune the string to make the same note. Tuning forks or pitch pipes can also help.
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Chapter 10: More about forces What is a force? Exercise 10.1 1. 2. 3. 4. 5.
push, pull, twist speed, direction friction pull gravitational
Spotting forces Exercise 10.2 1.
Scientists use the word ‘elastic’ to describe materials that return to their original size and shape if stretched or squeezed.
2.
If the spring in a force meter is pulled too hard, it might pass its elastic limit and will not return to its original length any more. The force meter will therefore become inaccurate.
3.
(a) A book does not fall through a table when placed on it because the downwards force (weight/gravitational force) is balanced by the reaction (support) force created by the table. (b) The ice on a pond may not be thick/strong enough to create a reaction (support) force that is strong enough to balance your weight. You could therefore fall through the ice into the cold water below.
Exercise 10.3 1.
The support force made by water is called upthrust.
2.
The canoe floats because the water creates enough upthrust to balance the weight of the canoe and the person inside it.
3.
The heavy boots worn by divers increased their weight. The human body only just floats so the extra weight is enough to make the diver’s weight greater than the upthrust from the water.
Exercise 10.4 Extension question A steel nail has a small surface area and therefore there is not much space for upthrust to work on to support it. A large ship, although heavier, has a much larger surface area and so the water can support it.
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Note: A ship is also largely filled with air. This makes the density of the whole vessel considerably lower than that of the solid nail. Although the ship’s total mass is huge, its density will actually be lower than that of water (1 g/cm3 or 1 tonne/m3) whereas that of the nail will be about 7– 8 g/cm3.
Exercise 10.5 1. 2. 3. 4. 5. 6. 7.
arrows direction length balanced longer tail centre of gravity
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