An Early Start to the Earth and Space
Roy Richards
SIMON & SCHUSTER ----~ ·--IN I 11i1'111 N20739 The atmosphere 38 Air is real 39 The Earth as a planet 4 Air pressure 40-41 Rocks and soils 5 Air pressure - a history 42-43 Crystals 6-7 Air pressure and flight 44-45 Soil constituents 8 Composition of air 46-47 ~IAT\ONAl W~ter and humus content of soil 9 Air pollution 48-49 ,&oil size and porosity 10 ,'" Soil acidity 11 ", Spil erosion 12 Shadows 50-51 Soil fertility 13 Sundials 52-55 Soils and decay 14-15 The seasons 56-57 Disposal of waste - sewerage 16-17 The Sun 58-59 Solar heating 60-61 The day 62 The water cycle 18 The hour 63 Water as a solvent 19 The month 64 Water pressure 20-21 The year 65 Water and surface tension 22-23 The Moon 66-67 Floating and sinking 24-27 Timers 68-69
Text © Roy Richards The planets 70-73 Artwork © Tony Morris/ Linda Rogers Associates The stars 74-75 Plants 28-29 The Shuttle 76 First published in Great Britain in 1993 by 30 Simon & Schuster Education Classification of plants Rockets 77 Campus 400, Maylands Avenue Sorting and separating plants 31 Hemel Hempstead, Herts HP2 7EZ . Animals without backbones 32-33 All rights reserved Animals with backbones 34-35 Classification of animals 36 Printed in Great Britain by BPCC Hazell Books Sorting, separating and studying Paulton and Aylesbury animals 37
A catalogue record of this book is available from the British Library
ISBN ° 7501 02357 Introduction 3
This book considers those parts of the National Safety in schools Curriculum Science Programme that are not covered in the other books in the 'Early Start' All the activities in this book are safe provided series. It is particularly concerned with water, the they are properly organised and supervised in atmosphere and the structure of the Earth. The accordance with the recommendations of the variety of life to befound on Earth is outlined. DES, the Health and Safety Executive, the Both the Earth's place in space and other bodies Associationfor Science Education, and local in space are considered. authority regulations. Any teachers who are uncertain about safety in scientific and technical Like the other books in the series, it introduces work should consult their LEA advisers. They children to the processes of: should also read 'Be safe: some aspects of safety in science and technology in primary schools', • exploration of their environment in order to published by the Association for Science gather experiences at first hand Education. • manipulation of objects and materials • observation of things around them Always pack away potentially dangerous • questioning and arguing about things apparatus and chemicals immediately the activity • testing things out, performing simple problem is over. solving activities • looking for pattern and relationship. Red triangles
Together with the other books in the series: Some activities in this book do require extra care and attention. They are marked with a red An Early Start to Science triangle. Under no circumstances should children An Early Start to Nature be allowed to pursue them unsupervised, An Early Start to Technology from Science particularly during breaks. An Early Start to the Environment An Early Start to Ourselves and Evolution An Early Start to Energy . it provides comprehensive coveragefor teachers of the whole Science National Curriculum up to Key Stage 2. The activities are presented in a highly visual, easily accessibleform. They stress the importance of scientific method as embodied in Attainment Target 1, Scientijlc Investigation, and at the same time give thorough coverage of the scientific knowledge outlined in the other attainment targets. The aim of the series has been to create a succinct, informative, accessible and manageable schemefor National Curriculum Primary Science.
I hope you enjoy the activities in this book.
Roy Richards For many thousands oj years people believed the Scientists speak oJ the Earth as having three Earth was flat. main layers: • The central core is about 6,000 km wide and made mostly oj iron. The outer core is liquid and the inner solid. • It is surrounded by the mantle, which is about 2,900 km thick and is made up of dense, very hot rocks, mostly solid but with some molten material. outer core / -t-.+ r' J {II •. • The outer layer on which we live is called the I / I .Iii ,'C1/0 crust. Under the oceans it is about 6 km thick I I / / i ; r inner core , I I I{ but under continents it is between 30 and 60 km thick, the thickest parts being under the mountain chains. The crust holds the oceans, known as the hydrosphere. The crust is surrounded by the The Earth is slightly wider across the Equator atmosphere, which extends upwardJor thanJrom pole to pole. Its average diameter is thousands oj kilometres, though most oj the air about 12,740 km. The Earth's mass is about is in the lower layers - at 60 km air pressure is 6,000 million, million, million tonnes. Three-fiftiis only a thousandth oj that at sea level. oJ the Earth's surface is water, two-fifths is land.
The Earth is one oj nine planets in our solar system. Its size relative to the Sun and the other planets in the system is shown below. OJcourse, this diagram does not show their relative positions.
Sun There are a number oj ways to begin a study oj the rocks and soils in the vicinity oj the school. A good start is to SECONDARY (Mesozoic) collect rocks from the immediate area. Such a survey is described in 'An Early Start to the Environment', pages 64-7, Jurassic-Oolitic limestones liassic (Jur.), Triassic and Permian -Sandstones and Clays where tests to carry out on rocks and pebbles are also described. PRIMARY (Palzozolc) Carboniferous-Coal Measures. Limestone and Millstone Grit With older children a study oj the solid Old Red Sandstone and Devonian geology map oj the area is helpJul in Ordovician, Silurian and Cambrian relating rocks Jound to the underlying ANCIENT (Pre-Cambrian) Torridonian. Longmyndianetc. strata. Outcrops oj rock and quarries in an area can also be useful for providing specimens. Scientific suppliers are a source oj named specimens oj rock. Soil • Soil isJormed by the breakdown oj rock through weathering and the addition oj organic material (decaying plant and animal material).
Sometimes soils bear no relationship to the underlying rock. Such soil has been transported by water, by wind or often by ice sheets in the Ice Age.
•......
See 'An Early Start to Nature', pages 58-9, Jor further work on soils. West from Greenwich a East from Greenwich
Geological map oj the British Isles When children examine rocks they will notice that a Growing larger crystals number are made up of, or contain, crystals of different shapes, sizes and colours. Crystals are not uncommon Potash alum (aluminium potassium in a child's world, for salt and sugar sulphate) will give good sized and bath salts are found in the crystals. home. A start can be made by examining these. 1 Dissolve as much as possible in a health salts (usually mug of warm water. sodium bicarbonate and citric acid; they 2 Hang a length oj cotton from a pencil so react in water to give that it dangles into the mixture. Epsom salts sodium citrate) bath salts (magnesium 3 LeaveJor afew days. Tiny sugar (mostly sodium sulphate) crystals will start to appear on the (sucrose) carbonate) thread and in the mug.
Salt 4 Remove the thread very gently Jrom the mug and suspend it in a Put some hot water into a Pyrex bowl and stir in clean jam jar. salt until no more will dissolve.
Pour some of the mixture on to a saucer, taking care not to pour out any undissolved salt. Leave it in a warm place for the water to evaporate. 5 Gently fill thejar with potash The slower the evaporation, the bigger the alum solution. Cover it with a crystals. clean piece of cotton cloth to keep the dust out. Leave. You will be left with a crust of cube-shaped crystals. Examine them with a hand lens. Try crushing the crystals - they will break into smaller, cube-shaped crystals.
Although it is important to show The crystals grow as the solution children that crystals can be becomes more concentrated through obtained in this manner, the results evaporation oj the water. are not impressive. Examining dry salt crystals with a hand lens or Chrome alum and copper sulphate binocular microscope will give better are two other crystals commonly definition of crystal shapes. grown.
Try growing other crystals in this way. Make a crystal garden Crystal shapes
Crystals can also be set into sodium silicate Crystals come in geometric shapes. These solution, where they "grow', giving a pretty effect. are some: Sodium silicate solution is somewhat gelatinous and was formerly used, under the name of 'waterglass', for preserving eggs. This is best done as a teacher demonstration as 4~---~7) some of the chemicals are poisonous. \ f .~_ / Begin by diluting the sodium silicate cube rhombohedron hexahedron octahedron with an equal amount of water. Put it in a largejamjar. Nets for a cube, rhombohedron and hexahedron Drop in two or three of each kind of are easy to construct. Here is onefor an crystal that you want to use. octahedron.
Use nets to make each of these crystals shapes from card.
Samples offluorite, quartz, rock salt and calcite are available from scientific suppliers. They are all excellent examples of crystals. Match your card models of crystal shapes with the crystals.
Fluorite and rock salt are cubic. Quartz and calcite are hexahedra. Calcite cleaves (splits) into rhombohedra. Fluorite cleaves into octahedra.
Crystals that give good effects are: potash alum (aluminium potassium sulphate) ferric alum (ferric ammonium sulphate) copper sulphate nickel sulphate manganese sulphate cobalt chloride rock salt Some crystals grow very rapidly. (sodium chloride) calcite Leave the garden overnight. Don't move it. The set thejar where you quartz (calcium carbonate) crystals will 'grow' upward in wavy strands. want the garden to grow (silicon dioxide) ------
Soils are composed mostly of fragments of rock. Back in school, take some of the soilfrom one bag and break it up quite finely. Use a trowel to dig up soil from the soil surface to a depth of 15 cm. Put it in a plastic bag. Dig soil Put this into a clear plastic bottle, almostfill with from a depth of 15 cm to a depth of 30 cm. Put water, put on the stopper and shake for afew this in a second plastic bag. minutes.
Secure each bag with an elastic band, and Repeat the procedure with label it. the soil from the second sample.
The largest soil particles (gravel) settle first. The finest (clay) settle last.
It is possible to estimate the amount of each in the sample. For example, if the gravel measures one-fifth of the height of the solids in the bottle then it is 20% of the sample.
):~f\
(·-~~-----l -I - ~ >li>
-i/----cl ay -=--~+---clay -..,,+--- si It ----_.----:;.-.;,,\---silt ---~,.,.,....-."..,.. ~+---sand
first sample second sample Water content e r-- rn3 2 1 f How mu.ch hu.m.us is thesai.l1_tr,<:3~L ' I•. ~[--Moss;of:tint~-U.d +d.ried:.~~~soiL..: 28 --.------~:~~~:~~J jHarce.nta. e
t. .J ~-.----~! ~~.~=n..~~~. t~:s~~~~~~h..t~~~;;~~,~~~~ ~- ...•...... -.i.no.. .ss d.fllii Wj.•... . =·2Q9~-~=- ~~-t~M=oJsoiJ.. . .•. Humus content .~=.1?~9~~~~=!
Again do this with both soil samples. t~--M(ASS (Jj -tin lid: + sotA(a.Jte.r heatLn9) --= 2~3~--~~
The relatively gentle heating in the previous L=F1~iOJ~Ci4-::=·~:·· __::_~~:::~-::[Q3:=l experiment should have driven off the water but not destroyed the humus (decaying plant and _-~l:1~~~~._9.f.s·Cs\($~.(.'--n~l.09)._., . :"._~~::.~::~___~~~~='! ~~,9 Again you need to use the two separate samples animal material. oj soil that have already been collected. The soil in each sample from the previous _~_A~~t.--Qf water' lost == 'IOg~89 ==7~'g:~-~-~~--" Weigh a tin lid and make a record oJits mass. experiment now needs to be cooked in a very hot I oven until the humus is bumt off. Put some soil in the tin lid and reweigh. Make a record. Make sure the tin lids are cold beJore reweighing.
Heat the soil at 1DDoCover two school days until Compare the amount oj water and the amount oj it is dried. Let the tin lid and soil cool. Reweigh. humus in the top layer oj the soil (to 15 cm deep) I 10
with that in the next layer (from 3D - - 15 cm to cm ------~ . .-:"""""'" .•.•.....- Repeat with the second soil sample. deep). Size Porosity
You need a sample oj soil that has been Take two identical yoghurt pots. Make a mark thoroughly dried in a slow oven. halfway down the side oj each one in exactly the same place. Make a hole in the base oj one. Cover Pick out any small stones ,then grind the soil with the hole with a piece oj blotting paper. a pestle and mortar to break up any lumps. . /) . Fill the tub with the hole half Jull oj soil to the · mark. Put it in the neck oj ajam jar. Weigh the sample. ~ , · ., Half fill the other tub with water to the CD mark. ~4 Pour this water on to the soil in the tub. Take a set oj soil sieves with meshes oj 2 mm, 0.2 mm and 0.02 mm (availableJrom scientific How long does it take for the suppliers). water to start dripping through? Put the soil in the top sieve and shake the tower oj sieves thoroughly. Children can take it in tums How long does it take for all for about 15 minutes. the water to drip through?
What colour is this water?
Pour the water Jrom thejar back into the original tub.
Does it come back to the original mark?
0.2 mm sieve 0.02 mm sieve receiving bowl
Particles Jrom the 2 mm sieve represent gravel Particles frotri the 0.2 mm sieve represent coarse sand SOIL DIAMETER ParticlesJrom the 0.02 mm sieve represent fine sand Caar.se. sarcd; 2-0 to o-z ov» Particles in the receiving bowl represent silt plus clay FiruL. SOJt.d.. 0-2 to O'02mm Try dUferent soils. SiA.;C If you weigh the particles Jrom each sieve you can 0·02. Which hold most water? Which allow water through work out what percentage they make oj the initial less tha..n. 0·002 rnm mass of soil. Cl~ easily? Some soils are acid ('sour'). Some soils are Put about 1 cm depth of the cabbage water into Lime also flocculates soil - that is to say, it alkaline i'suieet'). two identicaljars with lids. causes soil particles to stick together, forming lumps which give the soil a better crumb structure Universal indicator is used to test them. Add white spirit vinegar to onejar drop by drop and leave spaces for good aeration. Alternatively, you can also use a soil testing kit until the liquid in it goes red. boughtfrom a garden centre. A colour chart is used to match the colour in the test and tell how Add a spoonfuLof your soil sample to eachjar. acid or alkaline the soil is. Put on the lids and shake.
Fill two liddedjars with water. Put a tablespoon offine clay into each. Shake thejars.
What happens?
If your bluish liquid. turns red the soil is acid. If your red liquid tums bluish the soil is alkaline.
Make a soil acidity map of the soil around the acidic neutral alkaline school grounds.
Fill about a third of a test tube with distilled Adding lime water. Add a little soilfrom your sample. Shake. Add 2 or 3 drops of indicator. Match the colour. Lime makes a soil less acid, 'sweeter' as the gardener might say. Use slaked lime not Make your own indicator quicklime for these tests. Be careful not to get lime on your hands or clothes in these tests. You can make your own indicator by chopping and boiling red cabbage. It gives a bluish liquid. Make a solution of distilled water and white vinegar. This is an acid solution.
Add two or three drops of universal indicator, or red cabbage water. Both will give a red solution. Put a spoonful of lime in onejar. Shake bothjars again and leave them to stand. Add a little lime. Shake. Keep adding lime and shaking. You should get a colour change towards The water in thejar with lime will be clearer after the alkaline colours on the colour chart. a while than the water in thejar without lime. Soil is often blown away by the wind or washed Does compactness of the soil prevent erosion? away by water. Pour a full watering can of water on to each soil Wind erosion sample.
This can be demonstrated Examine what collects in with a hairdryer and the bucket each time. various soils. plastic What happens if you keep lined box on watering?
with a piece of turf
.. J. dry topsoil Does the method of ploughing affect erosion?
Water erosion Fill each box with soil but make differentfurrow patterns in the soils. For all these experiments you will need thick Predict which will give greatest runoff. cardboard boxes lined with plastic sheet, with a hole cut at one end. Pour equal amounts of water on each.Where is there most runoif? Water washes soil away Try other pattems.
sand
many many longitudinal transverse furrows furrows rdboard box lined with plastic sheet
Hose the sand with water. Start gently. What happens?
Continue more vigorously. What happens?
What happens if you increase the slope of the box? 1 Cut the tops and bottoms off 5 Keep a record. Stick a different coloured strip oj paper on the some plastic bottles (2 litre graphs jor each period oj time that you take a lemonade bottles are ideal). 40 reading. The readings need not be at regular 2 days intervals - when you remember will do! 2 Invert the tops into the bottoms. Cut strips oj cotton 6 Try different amounts oj liquid houseplant jabric to act as wicks. U) lO~s fertilizer. 30 ..~LJ QJ 4 d.aJjs .~ -~-~ .v 3 dAys potting compost § 20 wick .S 3 d.aJjs 3 Put the growing medium - soil, sand, or potting ~ compost - into the inverted top half oj each. Make sure the wick is well placed to soak up /0 4- d..0Jj5 water, or water plus liquid fertilizer, jrom the l' lower half. 10 d.OJjS
I 5 drops I per 500 ml
sana garden soil potting compost What kind oj growth do 30 you get with fertilizer? Soil shrinkage Clay soils dry up quickly in summer, and shrink and crack.
Rollout some moist clay about 1 cm thick on a ·20 ruler. Trim the edges with a knife, so that itfits exactly and is easy to measure as it shrinks. sand + garden soil + potting compost + liquid fertilizer liquid fertilizer liquid fertilizer Leave it on a windowsill in the sun.
4 Plant half a dozen wheat. JO Measure it daily. barley or oat seeds in each pot.
Mark one shoot with afibre pen when it appears. Measure it as it grows. Dead plant and animal material is broken down Make a list of things which are suitable for the .•Thln9S not sw.to..b\.Q. jor in the soil by bacterial action - it decays. The compost heap - list those which are not suitable efficiency of the action depends on whether the too. 0.. compost he.ap bacteria have enough air and moisture.
One of the most familiar experiences ------~-~-~-.~-.-'"--- r ThLt\gS suitable. jar o: compcst he.o.p of this process is composting garden waste. Ij tne schoolkeeper has a ~~ •• ~~'~ f,• .wrt'!f"f compost heap it would be useful teo..le.cwes to ask him or her to show it to the children and talk to them about it. dise0.5ed pla.nts
From discussion and examination of a compost heap it should be possible for children to draw up a table of the things neededfor good decay.
In the natural world the bacteria would not be This is aformula for a typical compost heap. It helped in their growth by sprinklings of should not be too high or too compact or it will nitrogenous dressing or lime. They have to start lack air. About 1 m is high enough. to break down plant and animal material, and get their nitrogen and calcium from that.
3 em soil with sprinkling of Neede.d jor deco..y sulphate of ammonia to provide nitrogen Boc.teri..a. - in tne. soil. ftrr - ..for the b~c.teri.o. to te.spLre. 20 em plant refuse Wo.±e,r - joy- the bo..c.te.rLo.. to use. 3 em soil with -'*f---sprinkling of Moist nUlYlu.s - pLa.nt a.nd. a.n.lrY'\o.l mate.rlol.. 10 em mashed tough sulphate of ammonia vegetable material e.g. cabbage stalks Nit'f'o9<2.ncru.!) d.re55Lng-ne.edecJ. b~ ba.cte.rL~ for drainage Lime. - n~e.cA bj ba..c..terLo... wire netting Great care has to be taken in dealing with a topic damp soil Observing decay cotton wool such as decay because oJthe danger oJ microbes. Observing the decay oj plant material on In order to examine the effect oj soil in this the compost heap is a useful. experience .1 "\ process it is useful. to bury a range oj Jor children. but it is possible to observe objects. You can do this in a decay oj soft things at doser quarters. herbaceous border or garden However. this has to be done very " plot. but it is sometimes carefuiiu. Usejars with tight screw top difficult tofind things lids. afterwards! / Make a hole in the top oj eachjar and ~~. \ hh plug it with cotton uiool. This lets the air ~~~~\ circulate but keeps microbes in thejar. ~: -. Put various things in thejars. half a tomato Put thejars in a warm place in the classroom, perhaps on a windowsill in the sun. Keep one or two jars with soft Jruit in a cold place to investigate the Select oj range oj hard things and bury them in effect oJ temperature. damp soil inside a large biscuit tin. Keep recordsJor 2 to 3 weeks. Bury this just below the soil surface outdoors. Moulds will certainly show on something , '~'~sliceof Examine the contents once a weekJor 3 weeks. like damp bread. These are Jungi and ~~ banana wearing gloves. they too act as agents oj decay. They are saprophytes. that is to say plants that Effect Jeed on decaying material. Object Wee.k I Week 2. Wee.k Disposal of material ~ 5p~ At the end oJ the experiment take thejar outdoors without the children present. Remove the lid and gently fiU thejar with a dear disinfectant, e.g. 'Clearsol', 'Stericoi', Co~c.. . 'Sudol'. Include the cotton wool plug and leaveJor 24 hours. Then dispose oj the large plastic sheet contents. or newspaper covering the table o.: \",
\ ,,5'
I' ~ A visit to a sewage works is useful for older juniors because all the processes are open to view and. with a good preliminary briefing. children can understand what is happening.
Wastefrom lavatory pans. baths and sinks When the sewage first passes to the sewers. as do rain and street arrives it is passed through washings and waste JromJactories. All this is mesh screens to remove taken to the sewage works. where bacteria play wood. plastic, rags and so a significant part in its breakdown. on. This material is either cut up and returned to the flow or removed and disposed of
The sewage now passes to primary sedimentation tanks where it remains Jor Jour to The sludge from the primary settlement tanks is six hours. Here the solids. called 'crude sludge'. pumped to digestion tanks. Here it is broken settle on the bottom. down over a two to three week period by microbes. The methane produced by this process can be used to generate the pouier required to run other parts oJ the plant. The remaining sludge. called 'digested sludge'. can either be used on the The liquid from the primary sedimentation tanks land. after some oj its water has been removed, or passes to aeration tanks. Here it is broken down dumped at sea. by mixing it with compressed air and microbes. This process take about eight hours.
(At smaller works. percolating filters do the samejob as the aeration tanks. Here the liquid is sprayed onto a bed oj gravel in a tank. then it breaks down as it passes through the gravel.) The liquid from the aeration tanks now passes to the final sedimentation tanks. The microbes are separated Jrom the liquid. which is usually dean enough to be released into a river. A sewage works can be modelled with cardboard boxes and plastic cartons. Pieces of plastic tubing can be used to simulate pipes, orjumbo art straws could be used.
Label the various parts according to the diagram on the previous page.
small open cardboard box
Plasticine join Bacterial action on waste J ~- Around the home material causes smells. In ! I the home we have an Ask the children to look around at home and S-bend to the lavatory pan, and under the sink, basins "" I 1 Make a sketch of how rainwater from the 2 Make a rubbing of a drain cover. and bath, to prevent gases roof reaches the drains. from risingjrom the drains. Make a model to show this.
I I--=-=--- thin wire looped around the I tubing to hold it in place Steam is a gas. When it cools it tums to liquid water vapour water, or to water vapour which can be thought of as tiny drops of liquid water hanging in the air. -. All air contains some water vapour. When there is a lot we see cloud or mist.
Warm air can hold a lot of water vapour. As air cools it can hold less, and the vapour condenses toform drops of liquid. This is what happens on the cold plate.
True steam is invisible. Look at the clear zone next to the spout of a boiling kettle. After a few centimetres it begins to condense to isible water vapour.
Holding a lit candle here extends the invisible zone,for it heats the air at this point.
Evaporation
Evaporation is a common phenomenon, but it needs discussion. It too can be demonstrated. The amount of water in the world remains constant and goes through a cycle. Water evaporates from the oceans, lakes and rivers to form water laden clouds. These are moved by winds. When they reach a region of cold air the water vapour condenses and is precipitated as rain or snow. This soaks into the land and runs via streams and, rivers to the sea. The water evaporates again and so the cycle is repeated over and over again.
puddles drying out after rain Condensation
This can be demonstrated by causing cold plate steam from an electric kettle to hit a cold wet coat drying surface such as that provided by a plate or saucepan lid.
All experiments with boiling kettles washing on a line should be performed. only by the teacher, wearing thick rubber How quick? gloves. One gram of steam at 100°C delivers as much heat I, A good open-ended investigation is to give groups to your skin as 5 g of iron at saucer of water of children 20 ml of water each. Which group can 1000°C. on a radiator devise the quickest way to get it to evaporate? Adding things to water Hard water Salt, sugar and washing soda A hard water is one which does not lather readily with soap. Hardness is caused by dissolve in water, sand and grit do the presence of calcium and/or magnesium salts. These can be removed by adding not. See 'An Early Start to Science', soap, which makes them come off as a scum. page 58, for activities.
Ca(HC03)2 + 2C17H35COONa ~ Ca(C17H35COO)2 + 2NaHC03 Does stirring help dissolve things? calcium sodium stearate calcium stearate sodium bicarbonate (soap) (insoluble scum) bicarbonate
Temporary hard water
This is water that can be softened by boiling.
Ca(HC03)2 ~ CaC03 + CO2 calcium calcium carbon bicarbonate carbonate dioxide Does heat help dissolve things? The dissolved bicarbonate changes to the insoluble carbonate which forms the 'fur' in kettles.
In the home temporary hard water can be softened by adding of washing soda (sodium carbonate). Insoluble things can be recovered by filtration; soluble things by evaporation.
'warm water Ca(HC03)2 + Na2C03 ~ CaC03 + 2NaHC03 calcium sodium calcium sodium bicarbonate carbonate carbonate bicarbonate (insoluble) Permanent hard water -I----funnel lined with blotting paper This is water that cannot be softened by boiling. The hardness is caused by chlorides and sulphates of calcium and magnesium.
Permanent hard water can be softened with washing soda. CaS04 Na2~03 ~ CaC.03 + Na2~04 calcium sodium calcium sodium sulphate carbonate carbonate sulphate Experiments on hard and soft water and on (insoluble) washing things are in 'An Early Start to Technology', page 86. Pressure and depth Take as tall a tin as you can find and make three holes in the side using a hammer and a nail. A Pour water through afunnei into a hose leading commercial size coffee tin is ideal. Put one hole to a balloon: A little water creates a lot oj about a third oJthe wayJrom the top oJthe tin pressure simply by its depth, and the balloon will and another hole near the bottom. Put the third swell. It will, oj course, get quite large as more hole in between these two. Cover the holes with a water is added. strip oj masking tape.
masking tape
.block of wood to help keep the shape of the tin
Fill the can with water.' Set the can alongside the sink and strip the masking tape off quicku]. pull ,Q."'t---:1+--- sta rt by making this loop
pull
The pressure varies with the depth of the water.
balloon deep high pressure
Do this outside Jrom afirst-jloor window - not indoors, in case the I whole thing comes undone or the balloon tied on tightly with string balloon bursts! Changing pressure Repeat the exercise but this time tilt the tin. Water level What happens? Another way to show the water pressure varying What happens as you raise and lower the plastic with the depth is to make a ring of holes around bottles? the bottom of a tin to start.
clear plastic bottles with bottoms removed
block of wood The push of water to help keep the tin in shape By making a slight variation to the tin you can use the water running out to make the tin spin.
Put the nail in each hole in the tin in tum and pull it sharply to one side. Try to keep the pull equal. Cover the holes with masking tape. as you gofrom hole to hole. Fill the tin with water. clear plastic tubing Hold it above the centre of the sink. pull nail this way Strip the masking tape away. What do you have to do to make the water jet bigger? What do you have to do to make the water jet smaller?
Hang the tin on a string. Cover the holes with masking tape. Fill the can with water. Strip the tape away and the tin will spin.
l~water jet
I~--tube from a medicine What happens to thejets of water the water as dropper level in the tin falls? Testing surface tension Water molecules attract each other slightly. The attractive force acts in all Fill a tumbler with water. directions. ???? Add more very gently! How far above the lip of the glass ~?~0? can you get the water before the At the surface there is nothing for the surface tension breaks? upward part of the force to act on, so instead it acts sideways. ~~~i0 Start with a glass that is full to the brim with water.
~~~~ Slide 1Op coins in gently from The result is that the surface of the water is pulled together, as if it were covered the side. with an invisible elastic film-but in fact there is no film, only ordinary water. The surface force, surface tension, is strong enough to support insects and small objects. It also gives drops of water their round shape.
The following activities give How many can you add before you break the children experience of surface surface tension and the water overflows? tension. Dry a small steel needle thoroughly. Balance Pond animals Gnat larvae hang it on a dinner fork. from the surface Look for pond animals that use of the water Very gently lower it on to the surface of the water this surface tension. in a dish. Remove the fork. in section whirligig beetle needle Gyrinus With luck, the needle will float on the water. -==-I!I-~-~ If you look sideways at the needle you will see the surface bending under the weight of the water needle. .. ~" If you have difficulty floating the needle in this way, try floating it on a raft of tissue paper (5x2 cm). After several minutes the tissue will sink, leaving the needle floating. water cricket Velia Dip a paintbrush into water. pond skater water measurer Gems Hydrometra Note how the surface tension holds the hairs together when it is See 'An Early Start to Nature', pages 52-5, for work on pond animals. withdrawn from the water. Surface tension on the move Drops of water Which can you pile highest in ajar? Water? Makefour or five holes close Put drops of water on to a ceramic tile. Note how Soapy water? together in the base of a tin they stand up. Cooking oil? can.
Fill the can with water from a bucket.
Hold it up.
medicine __ ------oliX' dropper
The water jets will flow out. Try soapy water, clear honey, clear honey and Now twist thejets together soap, cooking oil, oil and soap, turpentine or with your fingers. white spirit etc.
Take your fingers away. Make careful drawings of what you see.
The surface tension will hold thejets together.
Surface tension allows the liquid in a jar to build up above the rim without overflowing. Other forces saop~ clear c~a.r honey are: the wetting power of that liquid on a particular water hOYle.~ SOME REASONS WHY OBJECTS FLOAT Substances with a density less than that of water will But some things with air in them float in water. Those with a density greater than that will sink, e.g. a breezeblock. These are separated here for explanation purposes, of water will sink. but a number of them may be operating at anyone time. Because of surface tension Because of low density One way of comparing substances is by how 'heavy' they are. To compare substances properly requires taking the I same volume of each substance; or, put another way, / density:::: mass ,/ volume --~ coin See pages 22-23. Here is a table of density values. Because they are helped by having air in them Because of differences in pressure Substance Densi!y Substance Densi!y This block of heavy hardwood is floating just below (g/cm3) (g/cm3) tin can with the water surface. The pressure becomes greater the press-in lid Gold 19.32 Aluminium 2.70 deeper one goes in the water (see page 20). The pressure underneath the block is greater than the Mercury 13.53 Glass 2.6 pressure above it. The sideways forces balance each other, leaving an upward thrust on th~ block. Lead 11.34 Carbon 2.25 (graphite) low pressure Copper 8.94 Water 1.00 Iron 7.86 Softwood 0.60 Carbon 3.53 Cork 0.25 (dia.nondl medicine bottle Note that the density of water is such that each cm3 (mll has a mass of 19. Its density is thus 19 /cm3. aquarium high pressure Archimedes' principle Weighing a block of wood in water Archimedes discovered that if an object is totally If a block oj wood is attached to immersed in water it displaces its own volume oj a spring balance and lowered water. It is said that he thought of this in his bath into water, as the wood becomes and leapt out shouting 'Eureka'-which is a more deeply immersed, the Greek way oJsaying 'l'oefourui the answer'. reading oj the spring balance decreases. That is to say, the weight oj water displaced and thus the upthrust oj the water on the wood is increasing. Eventually the spring balance will register zero. The wood block isfloating because the upthrust (the upuiard force) in equal to its own weight. When a body floats it displaces a weight oj liquid exactly equal to its own weight. Iron ships Archimedes did a lot oj work on the upward Iron, even when completely immersed, displaces a thrust oj liquid on objects immersed in water and weight oj water less than its own weight. It thereJore other liquids. sinks. The classic experiment Tofind the upwardJorce oj a liquid on an object you need tofind the weight oj the liquid displaced by the object. Traditionally in physics this is shown by theJollowing experiment. block of metal Iron shipsfloat because they are hollow, andJull oj air. The The object is weighed on a spring balance. It is effective densiiu oJthe ship is the mass of the iron and the lowered into water in a displacement can. The large amount oj air it encloses, divided by the volume oj both. balance reading becomes less because the water is causing an upthrust on the object. The A ship can, oj course, be overloaded. If it is, it will lie decrease is the size oJthis Jorce. The weight oj dangerously low in the water so that waves may break water displaced can be read Jrom the dial over it andflood it. The Plimsoll markings on its side show balance. Archimedes says that the weight oJthis how deep it may be allowed to lie in various sea water will be equal to the upthrust. conditions. The bottom mark isfor the roughest sea. InJact these marks are measures oJmass, If-an object is immersed or partially immersed in like the marks on a spring balance. Plimsoll ajIuid, the upwardJorce is equal to the weight oj ~=i-I markings are shown in 'An Early Start to the can if' flUid displaced. Environment', page 83. .. t::WNA Practical experiments Suitable objects and materials to investigate: Keep a record. The previous two pages will have shown how • blocks and pieces of wood of all kinds (include complex are the issues involved infloating and a piece of lignum vitae, the heavy black wood Hoai» Si.nlu sinking. Young children can sort out objects that usedfor the 'woods' in the game of bouils=this float and sink but often give wrong explanations is denser than water) High Low Slaw~ QuicRly of why they float or sink, orfail to understand • rocks and pebbles what is happening. Cup shaped objects can • metals cause confusion because displacement is • glass, e.g. marbles involved. Pieces of kitchen foil or grains of sand • plastics, e.g. expanded polystyrene, solid can cause confusion because of surface tension plastic toy effects holding them up. • rubber ball • lumps of Plasticine One can go on and on with factors that might be involved and which might cause confusion. What Moulding Plasticine is important is to present children with a variety of experiences so that understanding will eventually develop. Here are some activities. Lumps of things Begin with lumps of things. It avoids any confusion over shape or whether things are hollow. Don't include things that will absorb water. Moulding Plasticine into cuplike shapes makes it float. Experiment with different shapes. Experiment with loads in the Plasticine boats. lump of Plasticine See 'An Early Start to Technology', page 47, for block of wood lS'N~ experiments with Plasticine and aluminium foil boats. How do weight and volume affect floating? Pushes and pulls Experiment with pebbles or marbles in a It is hetpfu: to draw children's attention to the sealed plastic bottle. pushes and pulls involved injloating and sinking in order to help them get a feelinq jor How does changing the number oj pebbles displacement. affect the way the bottle jloats? Lower a large block oj wood (1 kg) Where are the pebbles held in a net (like the one oranges when the bottle are bought in) into water. jloats? How does the biock fee! in air? How does it feet as it enters the water? Keep a record. How does itjeeZ as it goes deeper 5 pebbles 10 ~ble.$ I 5 pebbLe.~ into the water? What happens to the water level in the bucket? Tie a small rock to a sealed plastic bottle so that itjloats in water. Pour the water away so that the bottle is A 'submarine' lejt at the bottom of the bucket. Pour water in slowly. Cut two holes near the base oj a plastic bottle. Keep its cap on. What happens to the bottle? Load it with pebbles and put it inro What happens to the rock? a bucket oj water so that it sinks but stands upright on its base. Try it with larger rocks. Insert a 1.5 m length qf plastic Lower a block of wood into tubing. Blow. a completelu fuli bucket so that children can see the The bottle should rise andjloat. water that is displaced as itjloats. If it is too heavy remove a jew pebbles. Do this outdoors, of course! 28 Plants Plants which do not have flowers Algae mushrooms encrusting lichen bracket fungi on tree branching lichen seaweeds strictly speaking, fungi are not true plants, see page 30 leafy lichen Liverworts Mosses Fems cushion moss liverwort with leajlike thallus feather moss bog moss leafy liverwort hart's tongue fem Plants 29 Plants which do not have flowers Plants which have flowers Coniferous trees Monocotyledons (Gymnosperms) (seepage 30) onion wheat Dicotyledons (seepage 30) privet sweet pea '." labumum horse chestnut cabbage See 'An Early Start to Nature', pages 16-17, for a snapdragon classification of plants based solely on looking at daisy petals. 30 Classification oj plants Plants without flowers Algae Liverworts Small, flat, green leaf-like plants found in clusters, or ribbons, in damp places. All contain chlorophyll, the green pigment which is necessary for Pellia, Laphacalea, Lunularia. photosynthesis, but it is often masked by other pigments as in the brown and red seaweeds. Some algae are single celled, but there is a range right Mosses up to complex ones such as the seaweeds. Spirogyra, the green slimy Small leafy plants with the leaves spirally arranged filaments found in ponds, is a common alga as are the seaweeds. on the stem. Commonly found in compact cushions or as a carpet. Funaria, Sphagnum, Byrum. Fungi These are not true plants - they have no chlorophyll and hence cannot maketheir own food. They must live as Ferns saprophytes, that is to say on decaying material which is These have well developed roots and a made into a 'liquid' for ingestion, or as parasites. The main transporting system to carry nutrients through body is usually made of branching thread-like parts called their tissues. There are two generations in the hyphae. Pinmoulds, yeasts, mildews, mushrooms, bracket life history of a fern: a small, short lived plant fungi. which produces gametes; and a large, spore producing plant which in many instances lives Lichens several years. Male fern, maidenhair fern, bracken, hart's tongue fern, royal fern. Gymnosperms The ovules and seeds are These are composite organisms consisting of an alga and a fungus living in naked-i.e. they are not an association which both benefit from, that is to say in symbiosis. found in a seed box. Encrusting growths on rocks and rooftops are common. Rhizacarpan, Pine, larch, cedar, yew, Lecanara, Parmelia, Xantharia, CIadania. cypress Plants with flowers Monocotyledons Dicotyledons Narrow leaved plants with only one cotyledon ('seed leaf') in their seeds. Grasses, rushes, sedges, lily and orchid families. Broad leaved plants with two cotyledons in their seeds. Herbaceous plants such as dandelion, daisy, buttercup, sweetpea. Shrubs such as blackthorn, privet, box. Deciduous trees such as oak, horse chestnut, ash, lime, hazel, beech and apple. Non-deciduous or evergreen trees such as holly, laurel, magnolia and box. Sorting and separating plants 31 The ability to sort living things into broad groups Further work according to observable Jeatures is an important onefor children to develop. It comes Jrom Surveying plants around the school is discussed collecting, observing and investigating plants and in 'An Early Start to the Environment' (pages lO- animals, the mqjority oj which will beJound near 11) and many investigations on plants are . the school and home. Such observations will described in 'An Early Start to Nature'. Growing eventually enable children to mark living things plants and gardening are to beJound in 'An Early against keys using observable Jeatures oj Start to Science', pages 14-1 7. 'An Early Start to organisms. Ourselves and Evolution', pages 46-51 has a section on life processes and plants. Identification usually begins by matching living things against clear pictures in books. Growing plants Keys Growing and caring Jor plants in the classroom and the immediate school environment, and Eventually more precise methods are needed and thorough investigation oJ both cultivated and children leam to use keys. The idea of a key is naturally growing plants, eventually easy to establish by taking almost any collection begin to help children understand oj objects and sorting it according to paired the diversity oj plant life. criteria. The ability to group plants into the major orders described on the preceding pages comes from such understanding. The reJerences in the titles above give comprehensive coverage of this area of the National Curriculum Science Programme. There .are a number oj computer programs dealing with keys. 32 Animals without backbones Single celled animals (Protozoa) Two layered animals (Coelenterata) Flatworms (Platyhelminthes) common pond flatworms Paramecium Amoeba Segmented worms (Annelida) Spiny skinned animals (Echinodermata) Animals without backbones 33 Animals with jointed limbs ~Arthropoda) Myriapoda Insects (Insecta) bee dragonfly 34 Animals with backbones Fishes (Pisces) Amphibians (Amphibia) Birds (Aves) Animals with backbones 35 Mammals (Mammalia) Monotremes (Monotremata) Even toed ungulates (Artiodacty la) Rodents (Rodentia) Primates Carnivores (Carnivora) 36 Classification of animals ------~------~------ Most animal groups that children come across are listed here but there are others, e.g. Sponges (Porifera), Threadworms (Nematoda), Wheel animals (Rotifera), Sea mats (Polyzoa), Lamp shells (Brachiopoda). ANIMALS WITHOUT BACKBONES -INVERTEBRATES ANIMALS WITH JOINTED LIMBS - ARTHROPODA ANIMALS WITH BACKBONES - VERTEBRATES Single celled animals - Protozoa Crustaceans - Crustacea Fishes - Pisces Microscopic. Structurally very simple and very Mainly aquatic animals with two pairs of antennae Aquatic, move by means of a muscular tail and fins. abundant. All are found in water. Amoeba, and lots of paired limbs that are used for feeding, Breathe through gills. Body of many covered in Paramecium, Euglena. walking, swimming and breathing. Crabs, crayfish, scales. Salmon, roach, stickleback, pike, herring, shrimps, barnacles, water fleas, woodlice. 'plaice, shark. Two layered animals - Coelenterata Sack-like animals with the Amphibians - Amphibia opening to the sac being Partially adapted to life on land but eggs the mouth. Most live in the must be laid in water. Moist, shiny skin. sea. Hydra, jellyfish, sea Frogs, toads, newts, salamanders. anemones, corals. Reptiles - Reptilia Flatworms - Platyhelminthes Completely adapted to life on land. Scaly bodies. Eggs Small, flattened, unsegmented worms with no body protected by a shell and can be laid on land. Snakes, cavity. Some are freshwater animals often found Insecta lizards, crocodiles, turtles, tortoises. under stones and floating leaves. Many are parasitic. Body divided into abdomen, thorax and Pond flatworms, tapeworms, liver flukes. head. The thorax has 6 legs, and usually Birds -Aves bears wings. One of the most successful Characterized by feathers. Warm blooded. Segmented worms - Annelida and prolific of all animal groups. Moths, Specialized for flight. No teeth. Sparrows, ducks, These are true worms. They have a body cavity, a butterflies, bees, wasps, ants, penguins, owls, gulls, finches, robins. mouth and an anus. Included are the earthworms, locusts, mosquitoes, dragonflies, many worms that live in ponds, and the lugworms, flies, grasshoppers, cockroaches, Mammals - Mammalia ragworms and bristleworms found on sandy shores. earwigs, beetles, lice, termites. Hairy, warm-blooded animals. Young fed on milk produced by mammary glands. Duckbilled platypus, Molluscs - Mollusca Myriapoda spiny anteater, kangaroo, opossum, Tasmanian devil, These are soft bodied, unsegmented animals that Animals with lots of segments each bearing similar wombat, phalanger, man, lemur, loris, usually have one or more calcareous shells. Snails, legs. Centipedes are carnivorous with one pair of legs monkey, baboon, mandrill, gibbon, slugs, limpets, oysters, mussels, squid, octopus. per segment. Millipedes are herbivorous with two chimpanzee, orangutan, gorilla, pairs of legs per segment. shrew, mole, hedgehog, mouse, Spiny skinned animals - Echinodemata squirrel, beaver, lion, tiger, puma, Marine, unsegmented animals Arachnida mongoose, wolf, weasel, with the parts of the body Body in two parts with four raccoon, panda, polar bear, showing a radial symmetry, pairs of legs on the anterior sealion, walrus, seal, buffalo, usually along 5 radii. Starfish, part. Spiders, mites, goat, giraffe, elk, camel, pig, brittle stars, sea urchins, sea scorpions, king crabs, hippo, zebra, rhinoceros, tapir, cucumbers. ticks. hyrax, elephant, dolphin, porpoise, whale, bat. Sorting, separating and studying· animals 37 ------~------ Simpler classifications What to study in an animal There are many ways to classify animals. The Personaljacts classification oj animals outlined on the preceding • Common name. Scientific name. pages is a standard classification. Often. jor • Sex. Stage in life history (if appropriate) . . children, their own simple classification made up • Natural habitat. jrom readilu observable features may be the best to begin with. Appearance • Size. Shape. Texture. Colour. Good work with animals can be done with the invertebrate life jound around the school. It makes a good starting point jor sorting and separating. 'An Early Start to the Environment', pages 6-9, has a classification which is based on sorting and separating animals without . IDem backbones according to their number oj legs. Make coloured drawings to show these. Add a Collecting scale. Ways oj collecting invertebrate animalsjrom around the school are Behaviour described in 'An Early Start to the Environment', page 5. Housing • How it moves. What it uses to help it move. them and conducting investigations are to bejound in 'An Early Start • How itjeeds. What itjeeds on. to Nature', pages 36-47. This latter book also describes activities that • How it breathes. What it breathes through. can be carried out untb.fist). amphibians and birds. 'An Early Start to • How it responds to stimuli: Can it see? Does it Ourselves and Evolution' looks at life processes. . respond to touch? Does it smell things? Does it like warmth? Does it prejer damp places? Does Mammals it like the dark? • How it reproduces: Does it produce eggs? How Mice, guinea pigs, rats, rabbits, gerbils, hamsters many eggs? Does it look after its young? Is and other mammals are often kept by children or there a life cycle? Record its life history. housed in schools. Children are jamiliar • How it gets rid oj waste matter. Are there any with cats and dogs, and they come droppings? across the occasional wild animal such as a hedgehog, mole or badger Habit - they can, oj course, study • Is it a solitary animal or does it live in groups? themselves. There is much that can • Is it a territorial animal? be done. • Does it have enemies? • Does it affect its surroundings? Effects on people • Is it a 'harmful' animal? Is it a 'helpjul' animal? • Does it have to be controlled? How is this . done? Grouping • Can children place it in its group? 38 The atmosphere 500 miles, - - - - The atmosphere is the envelope of gases surrounding ground level are the troposphere, the stratosphere height with the latitude, season and weather. The the Earth. Its chemical composition is fairly constant, and the ionosphere. tropopause marks the level at which temperature but successive layers of the atmosphere display becomes constant, even with increasing height, for variations in properties: The main. layers starting from Troposphere the next 50 miles (80 km). All weather occurs in the troposphere. Air pressure and temperature decrease steadily as Stratosphere ..• ..• one moves upward. Winds, dust and water vapour are ,. present. Between this layer and the next is a thin ..• , transitional layer called the tropopause. This varies in This layer contains a thin ozone rich region just above the tropopause. The lower stratosphere is ideal for flying. Water vapour and dust are absent. Pressure upper ionosphere decreases as you move upward through the stratosphere, but temperature remains constant. Ionosphere Pressure decreases up to about 56 miles (90 km) above the Earth and then remains almost constant to the very edge of the atmosphere. From this height temperature increases upward. Water vapour and dust are absent. There are several electrically \ , conducting layers in the ionosphere; for example the aurora borealis is often seen in the lower ionosphere. The ionosphere also reflects radio waves around the world. \ \ \ Functions of the atmosphere \. \ As an insulator balloon , \ The atmosphere acts as an insulating blanket. It stops \ temperatures in middle and high latitudes dropping to stratosphere extremes during the night or during winter. As a filter The atmosphere protects us from those of the Sun's rays that are harmful. There isa thin layer of ozone in the stratosphere which prevents harmful rays from entering the atmosphere near the Earth. If this ozone layer is destroyed, life on Earth will cease. As an agent for the water cycle . Evaporation from the oceans produces water vapour, which condenses into clouds in the atmosphere and falls as rain or snow. Air is real 39 Air is invisible. Its existence needs to be made real to children. Shifting air Catching air Put a bottle into a bucket of water and let it fill ,up with water. Ask a child to take a plastic bag and scoop up some air. Hold it in the water so that it can receive bubbles of air Screw up the neck of the bag. from a second bottle plunged into the bucket. Keep a tight hold on the neck of the bag and squeeze it Air resistance with the other hand. Let a child run with a large piece of card held infront - the side from a large supermarket carton is a good thing to use. The child will be able to feel' the air. The push of air Try pouring some water into afunnel firmly sealed into the neck of a bottle. Use a bottle with a narrow neck. A dear glass wine bottle is ideal. Place a dried pea in the neck of a bottle which is laid on its side. Can the children blow it in? There must be something keeping the water from entering! 40 Air pressure Despite appearances air has weight and it exerts Air can break Air can glue a pressure. There is a lot of air in the atmosphere and it exerts a lot of pressure. In reality it Place an old worn ruler, on a table with half its Wet two plastic rulers, press themjlat sides squeezes all around us. Here are some things to length projecting over the edge. together. show this effect. Spread a newspaper over the table and over the Try to separate them without sliding them apart. Air can squeeze part of the ruler on the table. Suck the air out of a clean, thin-sided plastic Smooth the newspaper so that all the air is container. removed from beneath it. Give the ruler a sharp blow. Why is it dffficult? What is the effect of the water? What happens?' Two pieces of glass are even better! Air can hold Moving air Push a sink plunger on to a Place two identical books side by side with a gap smooth clean surface. between them. What holds it on? Put a sheet of paper over the gap. Damp the edges of two sink plungers and press Blow down the tunnel. them together. Try to pull them apart. It usually breaks sharply, illustrating the air Does the sheet blow away? pressure over the large area of the neuispaper.. How does the birdfountain A thin ruler and practice make for a dramatic on the budgerigar cage Why is it hard to do so? demonstration. work? Air pressure 41 Can you blow them away? Water and air pressure Take a medicine dropper and fill it with water. Hang two tin cans or two table tennis balls about Some of these tests are. messy, but they are fun. 2 cmapart. Do them over a sink. How does. it work? Blow between them. Fill a tumbler to the brim .with Fountain pens working on a water. Slide a piece of card sac principle are becoming What happens? over the top. popular again; These also work like the medicine Hold the card with dropper. one hand arid invert the tumbler. Take a tin can with a press-ott lid. Make one hole in the centre of the lid, and several holes in the base. If you carefully take your hand away from the card, it should remain in place, holding the water in the tumbler. . What is pressing on the card to hold the water in? Fill it with water iat a sink. Does it work if the tumbler is half full? Keep a finger over the Put a pin through the centre hole in the lid and lift of a piece of card. Place the The water pressure is pushinq the card down, but the the tin up. pin through the hole of a air pressure pushes it up. It is enough to stop the card cotton reel. and the water from falling. Blow through the other end. Screw a handkerchief into a ball and put it in the Can you blow the . base ofajamjar. card away? Invert thejamjar and push it, mouth downward, into a bucket of water. J. Take it out again. Take your finger off the hole. What happens? Relate this to the need to make two holes in a condensed milk can in order to get the contents out. 42 Air pressure - a history Evangelista Torricelli Mercury barometers are still used today. However, they are not easy to carry around and The history of the discovery that air presses on us are usuallu fixed. to one site. The aneroid ('dry') is an interesting one. Very shortly before he died barometer is easier to carry. in 1642 Galileo invited a young mathematician, Evangelista Torricelli; to come and work with him In such a barometer, air has been partly in Florence. On Galileo's death Torricelli became evacuated from a sealed circular box. If the air Philosopher and Mathematician to the Duke of pressure increases slightly it pushes harder on Florence. . this box. A set of levers fixed to the box causes a pointer to move over a scale. Torricelli had been experimenting with a long tube fixed. to the side of a building in tofind out order pointer about the column of water it would hold and the vacuum left in the tube above the water. This was cumbersome, so he hit upon the idea of using mercury, a liquid metal. Its density meant that he could use a much shorter tube. Torricelli believed, and was proved right, that the air pressing down on the surface of the mercury in the dish would hold a column of mercury. He thus invented the mercury barometer. knife edge pivot A mercury barometer isa tube sealed at the top so that no air can enter. Above the mercury in the tube is a vacuum. The mercury in the tube pushes levers to down but is held up by the air pressure pushing amplify on the mercury in the dish. movement The height of the mercury is read from the surface of the mercury in the dish to partial vacuum in thin corrugated steel case the level in the tube. At normal air pressure Bicycle pump this is about 760mm. A common tool used by children that depends on air pressure to work it is the bicycle pump. 760mm Pulling the handle back allows air into the lower region of the pump. Pushing the handle forward flexes the washer against the sides of the pump and thus forces the washer air outward. Air pressure - a h~tory 43 Blaise Pascal At the top of the mountain, which was about 1500 m high, he set up Torricelli's discovery became known to a his barometer again. The column of Frenchman, Blaise Pascal, who thought up mercury was now 6cm shorter than some experiments he wanted to try. before. Back at the monastery the Because he was unwell, and because he control barometer had not changed needed someone to climb a mountain, he throughout the day. got his brother-in-law, a Monsieur Perier, to do the experiments for him. The thinner air at the top of the mountain had held up a shorter On the morning of 19 September 1648, two column of mercury - that is, air clergymen, two lawyers and a doctor pressure decreases with altitude. gathered in a monastery at the foot of a mountain, the Puu-de-Dome in France. Otto Guericke Perier set up two mercury barometers and recorded the height of the mercury in each. It was exactly the same in each tube. He left one tube with the monks to keep a record of its height through the day and Otto Guericke was mayor of the took the other up the German city of Magdeburg. He mountain together was interested in making air with his five , ,,' pumps and experimented until observers. he had made a very efficient one. To test it hehad two cast-iron hemispheres made whichfitted together well. Using his pump, he extracted the air from inside the sphere and then had two teams of eight horses hitched, one to each hemisphere. Pull as they might, they could not separate the hemispheres against the outside pressure of the air. Page 40 shows how to simulate this using sink plungers. Theforces operating on an aeroplane injlight are Ask a child to blow over the Moving things through air discussed in 'An Early Start to Technology'. page top of a sheet of paper. 50. Here l.Deare looking at the force that causes Try running with a stiff piece lift in greater detail. for it is tied up with air of card held at an angle. pressure. Change the angle. Run again. Do the following experiments with children. Curve the front edge. Moving air past things Run again. Hold two strips oj paper a short distance apart and blow between them. The fast moving air over the top of the sheet reduces the pressure. The air pressure undemeath the sheet therefore forces the paper upward Wind on wings Take a sheet oj A4 paper andfold it in half. Curve Can you feel lift? and glue the top half to the bottom half toform an Can you feel drag? aerofoil shape. Make a hole through both sheets. Insert a length of drinking straw. positioning it between the two holes. air Thread a piece oj cotton through the straw. This principle of faster moving air causing a reduced Blow against the front. and then against the rear, pressure is used in an aircraft wing. oj the wing. What happens? The air moving over the longer top surface of the wing has to move faster. Theslower moving air underneath the wing presses more, and so the wing lifts. this distance is longer -. ==t> air rushing over the wing Children expect them tofly apart, but they come together. =====:::;C> The air pressure between them is reduced; the air this distance is shorter pressure on the outside thus Jorces them in. Air pressure andjlight 45 A paper glider 4 Fold in each comer. 8 Open out the wings - they must not be too tightly folded. There are various aircraft and other jlying things to investigate in 'An Early Start to Technology', pages 50-57. Here is another aircraft to make. It moves beautifully on the air. 1 Take a sheet of A4 paper. 5 Fold up the point of the triangle, tearing the 9 Testjly your plane. paper slightly on both sides. 2 Fold the two top comers to the centre. 6 Fold up along the centre' line. 10 Adjust the wingtips to tum right, tum left or loop the loop. 3 Fold the triangle that has beenformed to the centre. 7 Fold down the wings. loop 46 Composition oj air More on burning The amount of water vapour in the atmosphere varies. If we take dry air the volume composition is The part of the air that supports combustion is oxygen . • 78% nitrogen .21% oxygen Take three different sized glass jars with smooth rims . • 1% argon, with minute traces of neon, helium, Grease each rim with Vaseline or lard. Keep them krypton and xenon, and about 0.03% carbon dioxide. ready for inversion over birthday candles. Arrange three birthday candles on a Burning smooth surface - glass is ideal but a smooth plastic tray may do. Melt Put a candle stub on a tin lid and the base of each candle slightly float it on a little water in a to make it stick. large Pyrex bowl. Light the candles. Light the candle. Invert ajar with a Place thejars over the wide neck over it. candles all at the same time. How long does each candle bum? How does the volume of thejar compare with the length of time that the candle bums? Jar Volume. Time corrdla burns I 2 As the candle bums it uses up the oxygen in the air. The water rises to replace the oxygen that has been used. 3 Rusting Rusting uses up part of the air. It is often stated in experiments with burning a candle in a jar that 'one-fifth of the air is used up' or that 'the Jam some steel wool into the bottom of ajamjar. lighted candle goes out because it has used up all the Invert it over a little water in a bowl. Mark the oxygen'. Under experimental conditions that is rarely, level of the water in thejar. if ever, so. The lighted candle heats the air in the jar, causing it to expand. Some air is pushed out under Put it on a windowsill out of the way and leave it the bottom of the jar, and this air cannot get back in for some days. when the jar cools. In reality the candle uses about one-third of the available oxygen. What happens to the water level? Composition of air 47 ~------ The greenhouse effect Damage to the ozone layer The amount of carbon dioxide in the air has been The ozone rich layer just above the tropopause increasing over the last 100 years. Why? cuts down the amount of ultraviolet rays from the Sun that reach the ground. .., .•...,,;; "." ." , , /. ". , ,. Industry has increased. These are the rays that give us .••.,...y)t-ravj6Ievrays a suntan. They bum the skin. •••• ,," I I Fossilfuels give off carbon , I If the ozone layer is ,,I 'ozone layer dioxide when burnt. damaged too many of these. rays could Forests have been cut down. get through. ~ ~ c::7 tJ {} Seas have been polluted. fewer ultraviolet rays Loss of trees and death of seaweeds and plankton cut back on the world's 'photosynthetic bank' - the stock The use of CFCs (chlorofluorocarbons) in aerosol of plants which use up carbon dioxide-~ sprays, refrigerators, air conditioning units and and release oxygen. il the manufacture of expanded plastic foams, releases chemicals into the air. These pass up The carbon dioxide in the air acts as a blanket. Heat is prevented through the atmosphere and chemically react from escaping into space. This is called the greenhouse effect. with the ozone. Thinning has begun to appear in The carbon dioxide has a similar effect to the glass in the the ozone layer. This means that more ultraviolet greenhouse that traps th-eheat. radiation can penetrate the Earth's atmosphere, causing sunburn, skin cancer and eye damage. Extraction of natural gas, and farming, both cause the release of methane (natural gas is itself methane). Design a poster to alert people to the danger of This is an even more powerful greenhouse gas using CFCs. than carbon dioxide. Collect pictures of things that cause damage to Collect accounts from newspapers about the the ozone layer. Make a wall display. greenhouse effect. Make your own record too. Re..gl.an Ejfe.c.t Polar caps gettLng wo.rmer and melting. Se.o..le.ve.Ls c.ouLd rise b~ 6m. Europe. getting warmer. }Jossi ble. fLood Ln9· 5peci.a.l d iffi.cu(±Les for countr-ie.s liRe. HcLLo..r"\d. Ncrrth gettln.9 warmer· Draughts America o.ffectLng grain c.rops. Discuss ways to get their production curbed or banned. 48 Air pollution Acid rain nitrogen oxide combines with water to make nitric buildings and eats away at their exteriors. acid. When they Jall as rain, these acids, though Prevailing winds carry such pollution Jrom the Pollutants from vehicles, Jactories and power weak, can cause immense damage to plant life, United Kingdom to countries like Norway and stations combine with water in the air to make poison soils, build up in lakes, eat away at Sweden, which create little air pollution of their acid rain. The main pollutants are sulphur dioxide stonework and affect our health by being own. and nitrogen oxides. Sulphur dioxide combines breathed in and taken. in drinking water. The with water to make weak sulphurous acid, and acids can be present in dust which settles on Make ajrieze to illustrate the production and effects ojacid rain. Discuss possible ways ojdealing with the AH{ POLLUTI ()N problem ojacid rain: . • by reducing pollution • by turning to other energy sources that don't produce pollutants, e.g. sun, wind and wave energy (see 'An Early Start to Energy', page 70) • by liming acid lakes to neutralize the acid (a short term solution - see page 11Jor the effects ojadding lime). Make a display ojalternative energy sources. Air pollution 49 Pollen - a natural 'pollutant'? Hay fever Some of the grasses whose pollen can cause hay fever. Some children suffer from allergic reactions to Ask hay:fever sufferers to describe their pollen grains in the air. Flowering plants release symptoms and their treatment, e.g. sneezes, pollen, which is carriedfromjlower tojlower by itchy eyes, runny or stuIfy insects or transported by the wind. It is the noses, sensitivity to windborne pollen that is of concern to sufferers sunlig ht; treatment from hay fever. . by vaccines and antihistamines. The plants mainly responsible for this are trees and grasses. Wind-pollinated trees tend to produce their pollenfrom late winter to the end of spring and, in general, are not of great consequence in causing hay fever. However, large numbers of hay:fever sufferers are sensitive to the pollen of grasses, which is produced during the period from June to August. Temperature, humidity and the pollen count Much of this pollen is produced in country areas, timothy couch grass meadow grass but the wind often carries it into towns and cities. The amount of pollen in the air varies with the Hay fever is more of a problem than it used to be temperature and humidity. because the allergic symptoms are worsened by breathing polluted city air. Daily temperature and humidity can be recorded, Pollen count or taken from data published in the national Relief is brought when weather conditions change press. The pollen count is also published daily as The pollen count is the number of grass pollen grains as rain washes pollen out of the atmosphere. well as being announced on the radio and per cubic metre of air, averaged over 24 hours. television. June June June 70 e 350 11) E 300 o 25 60 :0 :::s u 250 o Q; 0 cf? 0. 20 50 e (/) :::s ?: .s 200 ro :0 e Q) C) 0. ·E :::s 150 E 15 .~ 40 C s :::s 8 100 c:: 10 ------~ 50 (50. 4 5 6 7 8 9 1011121314151617181920212223 4 5 6 7 8 9 1011121314151617181920212223 4 5 6 7 8 9 1011121314151617181920212223 50 Shadows My Shadow The rotation of the Earth Retum the same child to the chalk shoe marks through the day and draw the shadow cast. I have a little shadow that goes in and out The rotation of the Earth is an abstract ideafor with me, children, and even though the concept is readily And what can be the use of him is more than accepted by adults it still needs quite a lot of I can see, thought to marshal evidence to substantiate it. He is very, very like me from the heels up to the head; One of the major pieces of contributing evidence is And I see him jump before me, when I jump the apparent movement of the Sun across the into my bed. sky. For children, plenty of experience with shadows helps develop this idea. Both 'An Early The funniest thing about him is the way he Start to Science' (pages 26-28) and 'An Early likes to grow Start to Energy' (pages 15-17) offer a wealth of Not at all like proper children, which is experiences to be gained from shadow play. From always very slow; these experiences children will begin to For he sometimes shoots up taller like an appreciate that: india-rubber ball, • shadow length changes during the day And he sometimes gets so little that there's • shadows can be sharp orfuzzy, depending on none of him at all. the weather • the angle at which lightfalls on a particular He hasn't got a notion of how object will affect the shape of the shadow children ought to play, • the Sun changes height in the sky through the And can only make a fool of me year in every sort of way. He stays so close beside me, he's Tracking a shadow Altematively, use a broom a coward you can see; handle tied to a box. I'd think shame to stick to nursie as The easiest way to show the that shadow sticks to me. Sun's movement using shadows is to chalk round a child's One morning, very early, before the shoes first thing in the sun was up; moming, thus making a I rose and found the shining dew on . permanent mark on every buttercup. the playground. The But my lazy little shadow, like an shadow cast can arrant sleepyhead, then be drawn. Had stayed at home behind me and was fast asleep in bed. R.L. Stevenson Discuss the movement of the shadow from west to east. Try predicting where the shadow will be at various times of the day. Shadows 51 More work on shadows Shadows cast in the classroom can be another Alternatively, you could way to illustrate the movement of the Sun. make chalk marks on an The length of shadows cast by a old table to trace the stick through the day can easily Make a cross on the window with masking tape shadow cast by a window be turned into a histogram. Here and chart the shadow cast down the wall by frame. Again use a south- is one showing shadow length making crosses on mounted sheets of paper. Use facing window. at 30 minute intervals between a south-jacing window. 9 am and 6 pm. \ - ~ stwiowl~+ - r-- ,.--- - - Knowing the direction - - r- 1- It is essential in this kind of ~ r-- work to establish the r--- ~ - cardinal points of the I---I---r-- compass. If children are unfamiliar with the positions of north, south, east and west they will need to be taught. • 1.OCJ (om ".00 1240 13.00 11•.00 1'£0(1 ".()(; tUX) w.oo time Discuss how the shadows • show the Sun's seeming movement from east to .west. Tracinq these • • shadows at two or three • times through the year will also show how the Sun is .~ higher in the sky at some times of the year. 52 Sundials The apparent movement of the Sun across the sky At London, because of the curvature of the acted as the principal timekeeper for people such Earth, the North Star appears lower in the as the ancient Egyptians, and persisted as the sky and the tip of the gnomon must be main means of telling the time well into the adjusted to suit the latitude. Its angle here Middle Ages. The sundial, in many forms, is 51.5°. predominated. Basically, it consists of a triangular central piece called the gnomon (from the Greek workfor 'to know') which casts a shadow on a numbered scale of hours. Setting up a sundial In order for the shadow to movefairly uniformly At the Equator, where the North Star is right on over the face of the sundial the gnomon must be the horizon, the gnomon is horizontal, so that an set parallel to the Earth's axis. At the North Pole ordinary horizontal dial cannot be used. the tip of the gnomon would point straight up to the North Star, since the Earth's axis points in that direction - that is to say, it would have an angle of9~. L direction of celestial North Pole Because the shadow moves more slowly over the sundial at midday when the sun is overhead, you willfind that the numbers are placed closer together towards noon, and farther apart towards morning and evening. Sundials 53 Children can make many kinds of sundial. Equal angle sundial Set the sundial in an east-west direction for use. Here are some suggestions. This sundial has hour marks an equal distance Simple sundial apart because its card is aligned with the celestial North Pole. Take a piece of card and use a protractor to mark card gnomon lines 15° apart as shown. 2.5 cm 15 cm thick 30cm card or polystyrene Remember to make the angle of the gnomon Plastic water bottle sundial equivalent to your latitude, 51.5° for London. [Cutting the gnomon to the lengths shown above This also has equally spaced hour marks. will give a gnomon roughly suitable to this country.] 18 cm Either mark in the hours by obseroing the shadow throughout the day or use the table on north shadow of spoke Fix this to a stand with the angle shown at Y the next page. '" ~-- drawn in at equivalent to 900 minus. the angle of your latitude. hourly intervals Insert a needle to act as a gnomon. Portable Egyptian shadow clock These.were made of wood. front cut away First thing in the moming, set it from bottle facing the Sun so that the shadow bent bicycle of the pencil fall« on the crossbar. spoke In the aftemoon set itfacing west. The Egyptians indudedji.ve hour lines plus the spoke stuck noon line. into ground 54 Sundials A pocket sundial Stand triangle ABC up so that itforms a gnomon. c Set the sundial with the gnomon aligned with the Portable pocket sundials were north-south line, and pointing north. adult toys for the rich. They were made in wood, ivory, gnomon in line with brass, and precious metals. north-south line; pointing north Here is a simple one to make from card. It will fold up and go / ~I into an envelope. (l) .s:::1 "0/ c: Trace the pattern on to stiff card. .31 Cut it out. J 1 Cut along line AB. Score, I then bend along lines I < BCandBD. ------bend h e!:..e D Table for the gradations on the sundial Sundial time Angle for London (latitude 51.5°N) 6am 0° 7am 19° 8am 36.5° 9am 52° 10 am 65.5° 11 am 78° 12 noon 90° 1 pm 102° 2pm 114.5° 3pm 128° 4pm 143.5° 5pm 161° 6pm 180° Draw the 4 am and 5 am marks diametrically opposite the 4 pm and 5 pm marks, with the 7 pm and 8 pm marks diametrically opposite the 7 am and 8 am ones. Sundials 55 The Sun itself A plane table and a clinometer make it possible to plot the position of the Sun through the day. It must be stressed that children should never look directly at the Sun. The Sun's image is cast on to a·swivel piece. the Sun's image is cast Do not look directly at the Sun 180° Here is a sample set of results as plotted by children viewing the Sun from their school against prominent features of the immediate landscape. r------, I 60° I I J : 30° 0 ..r. 0-----° 1100------180°~ 260 , 13 Dec View from the school Sun's transit month by month 56- The seasons Discuss the seasons oj the year and list some oj the things What causes the seasons? that-characterize each one. The Earth's axis is tilted at an angle oj23.5° to the Spring Summer Autu..mn Winter plane oj its orbit around the Sun. Lam bing Hol.i.d.rujs Leo"] CDLau.rs Srvow If the Earth were not tilted 5 r..tnn:1 olo.ys we would have exactly 12 DaffodiLs Bonfire5 RobLJ'\S hours oj daylight and 12 free folW..g e. hours oj darkness, and no seasons. not this but this Because the Earth is tilted the number oj hours oj darkness and oj light per day varies through the year and we have seasons. Make a ftieze or a concertina folder to illustrate each season. The seasons 57 A model of the seasons Take a globe oj the world ona stand. It is fixed at an angle oj 23.5°. Set it to each oj the jour positions shown below, in a Many.primary school childrenfind the causes ojthe seasons darkened room Shine a torch at the globe jor each oj the jour dllficult to understand. The jollowing is a pictorial explanation, positions while someone turns it slowly and note the areas in the with a suggested simulation using a globe and a torch. Northem Hemisphere that are in light and in darkness. One will have more light than darkness, one will have more darkness than light, and two positions will have equal light and dark. equal light and darkness more darkness than light summer In December when the North Pole is tilted away from the Sun we have winter. In June when the North Pole is tiliedtousards the Sun we have summer. Halfway between these times the Earth's axis lies at right angles to the Sun and we have equal day and night - the equinoxes. It is as well to remember that not all parts of the Earth have seasons like us. At the Poles there are extremes oj day and night between summer and winter, and at the Equator there are only wet and dry seasons. more light than darkness The height oj the Sun in the sky as observed from Earth varies with the seasons. This affects both the number of hours oj equal light and darkness daylight and the temperature (seepages 55 and 59). ,58 The Sun The Sun is our source oj light and heat. It is the centre oj our solar Sunspots, which are dark patches system around which all the planets revolve. It is, oj course, a star on the Sun's surface that may cover and it is the nearest star to us. It is 1392,000 km in diameter and an area oj several thousand square occupies a space equivalent to about one million Earths. It kilometres, will show up on the generates energy by nuclear Jus ion oj atoms within itself. The imaqe: These spots on the sun temperature on the surface is 6000°C; inside, it may reach are up to 2000° C cooler than 15,000°C. surrounding areas. They appear singly, in pairs or in groups, Observing the Sun with a maximum activity period every eleven years. Daily It is dangerous to look directly observation will show change at the Sun, but you can project in size and show that the Sun a sofe image oj it on to a piece rotates on its axis. Weekly oJwhite card through a observation will give an idea oj telescope or a pair oj their activity over time. binoculars. Sunrise and sunset The times oj sunrise and sunset vary with the seasons. 'Whitaker's Almanack' gives times Do not look Jor the first oj each month. They are also given in some diaries. directly at the Sun Plotting the times oj sunrise and sunset for thefirst day oj each month through the year gives a graph like the one below. o).()O ..•.. Use a clamp, or some sort oj support, to botd. the card steady. or. 00 _ ~ -~ r-, piece of white card 07·00 ~ V ,/ ", , binoculars wedged on oCf·oo '- a block of Plasticine ,/ I /-00 1l1"V\-e. ().MT. 13· 00 ~- -- .. - -- 15'00 J 17100 -...... ~ •.. ~ IT·o () ~ V ~ """. 2.1 '00 r----.~ -~ 2. 3 .00 ~CAn F'~ Mllr Rpr Mo.:J :To/\(..-Sv1y Av'f ~~r- Oct- Nev DeL Mon",,", The Sun 59 The height of the Sun in the sky as observedfrom Earth varies Children can demonstrate for themselves the with the seasons. effect that is obtained angling rays of light. We are used to the short days of midwinter when the Sun is low in the sky and only appears above the horizonfor afew hours. The Sun's rays do not heat the Earth as much as they do in summer because the warmth is spread over a wider area, so the days are cold. In midsummer the Sun is at its highest point in the northern sky and it stays above the horizon longer than in the winter. There are more hours of daylight. The Sun's rays are concentrated on a smaller area, and the days are consequently warmer. In March and September at the equinoxes, the Sun's height in the sky is midway between that of winter and summer and we have approximately equal lengths of daylight and darkness. The angle at large area which the Sun's rays hit the Earth is between that shownfor winter and summer, and the temperature is also between the two extremes. .,..- _. midsummer Sun's position through the year ;';";" \ , The heating effect of the Sun's rays ,.";' J'I ,. ....•••..--. equinoxes falling fairly directly and falling at ,. ~~ an angle can be shown. ,." " " I \ midwinter I';' ,,/' I J __ '- I' "1 .i-:" Shine the light and heatfrom a light / / E" ""I , "'/ bulb on to a thermometer under a ,. "I SE,,"'''/ NE ,. ,. I square of black felt, which represents the Earth's surface. Use two similar lamps but beam the light directly from one, and at an angle from the other. Which thermometer heats up the most? NW W SW Sun's heating effect through the year midsummer midwinter sun equinox sun small area medium area large area 60 Solar The use of solar panels to capture energy from 2 Put 50 ml of water 4 Put the beakers on a sunny windowsill. The the Sun is becoming more widespread. into eachjar. jar covered with half aluminium foil and half black paper should have Investigate the heating ability of the Sun. You will the black paper facing the needfour small identicaljamjars. sun and thefoil facing the 1 Cover onejar with aluminium kitchenfoil, one jar with black paper, and onejar half with aluminium foil and half with black paper. 3 Take the temperature of the water in eachjar. Keep a record. Black paper absorbs heat, aluminiumfoil reflects heat (see 'An Early Start to Energy', page 36 and 43). 5 Record the temperatures of the water in the jars every 10 minutes. Tem~o.ture TIme Foil Bla.cR. B.lhper Cantrol (mins) paper + FoiL Leave thefourth jar dear as a control. {O 20 30 40 aluminium foil black paper Plot a graph showing temperature against time. Solar h~ting 61 Many modem homes have large south-Jacing 1 Cover the baseboard with kitch.enfoil. windows and small north-Jacing ones. Often there is a conservatory on the south side, and sometimes black solar panels on the roof All these help to capture heatjrom the Sun. . 2 Pin the clear plastic tubing to the baseboard in a zigzag shape with the wire. 3 Make a very small hole in the bottom of the bottle so that it will not leak when you insert the lower end of the tubing. The upper end should project a short way into the top of the bottle. Make your own solar panel Remember that dull and dark colours absorb heat, but shiny, 4 Fill the system completely with light coloured surfaces reflect heat. water. Cover the heater panel with a sheet of black paper. You will need the materials shown. Place it in the sunlight. _ black paper 5 Record the temperature at 5 minute intervals for 1 hour .. Time At top oj bottLe. At boltom stiff lOmins IOrnins wire f5mi.ns f5mins plastic bottle black paper See 'An Early Start to Technology', page 73, for details of how the same size to make a solar cooker. 'And God called the light day', and the darkness Timekeeping around the world The Pawnees used to cut notches he called night. And the evening and the morning in a stick to mark the passage were thefirst day. [Genesis 1:5J A discussion with the children on how other oj the nights. They denoted societies measure the passage oj time is a good night by the word 'sleep'. Timekeeping is based on a natural phenomenon - lead into thinking about timekeeping. the rotation oj the Earth, giving an interval oj one day. The Comanches oj North America drew hieroglyphs. The Earth spins like a top. The partjacing the A three-day joumey would Sun is in daylight. The partjacing awayjrom the be shown by three circles Sun is in night. representing Suns. Make up some hieroglyphs oj your own. Cut a tally stick. The Romans were thefirst to use night watches oj afixed length in. their army. The English names jor the days oj the week are derived from the Saxon, the French jrom the Also in North America, the Latin. Kiowas used a rich terminology based on the position oj the Sun in the sky. Days of the week Saxon English • Dawn -literally first light' Sun's day Sunday • Sunrise - .literally 'the sun Moon's day Monday has come up' Tiw's day (Norse god of war) Tuesday • Moming -literally full day' Woden's day (Norse god of storms) Wednesday This can be demonstrated in a darkened room. • Noon Thor's day (Norse god of thunder) Thursday • Early aftemoon (until Frigg's day (Wife of Odin) Friday 3 o'clock) Seater's day (Saturn - Roman god Saturday • Late ajtemoon of Agriculture) • Evening - literally first darkness' Latin French Dies Solis (Sun's day) Dimanche Dies Lunee (Moon's day) Lundi The Inuit oj Greenland reckoned Dies Martis (Mar's day god of war) Mardi time by the ebb andjlow oj Dies Mercurii (Mercury's day- Mercredi the tides. messenger of the god's) Dies Jovis (Jove or Jupiter's day- Jeudi ruler of the gods) DiesVeneris (Venus' day) Vendredi Dies Saturni (Saturn's day - god of Samedi agriculture) Turn the ball slowly. The hour 63 One complete spin of the Earth takes about As the Earth spins, zones pass from darkness Because the Earth spins from west to east, places 24 hours. This takes the Earth through 360°, so into light. The spinning causes the day to pass. west of Greenwich have their time later than in in 1 hour it turns through 15° (=360). Every 15° takes 1 hour. Greenwich. 24 Ask children to draw a circle and mark it at Here is an example. New York is about 75° west 15°intervals. of Greenwich. So it is about 5 hours i= 75) behind Greenwich. 15 line of longitude -----I'--F---;/ Use a globe of the world to look up the longitude of large towns and cities. Work out the time in each place when it is noon in Greenwich. 1-+-+-+-+----F-'---lI''----G reenwich . meridian Greenwich Observatory Much of the pioneer work in astronomy and in They wiilfind they have 24 segments. Each timekeeping stems from the Royal Observatory at marks a time zone. 'Greenusich. By international agreement in 1884 the line of longitude passing through Greenwich was declared the prime meridian and all time measured from it. PLace Lon gi..tu...d.e Time San Francisco 1200W 04- 00 Ca.nberro.. 150°£ 22 00 Rome 15°E 01 00 Acero. 0° 12 00 64 The month The Moon takes about 271/3 days to go around the Earth. That is Twelve lunations take 354 days. This differs by about 1114 days the time from the point of view of an astronaut in space. But from the solar year. (The solar year is the time the Earth takes to go 1 because the Earth is also moving around the Sun it takes 291/2 around the Sun, just under 365 4 days.) Our western calendar days before we on Earth see the Moon in the same position relative . divides the year into conventional months. These are quite to the Sun. This is called a lunation or lunar month; the true time is independent of the Moon and keep, as a reminder of their origin, called a synodical month. only a name and a length approximating to that of the Moon's revolution. () first quarter gibbous Moon O. ~ () I/i;\ cresc~nt Moon (waning). -> ~ ~ (waxing) Months of the year If) f)\. ¢: January - after the double faced Roman god Janus, who looks into both past and future . ~ February - after Februa, a Romanfestival ofpurification light from March - after Mars, the Roman god of war "",.".-;., full moon ¢: the Sun 0() (). April- connected with Latin aperire, 'to open', new because it is a spring month \ Earth ) moon May - after Maia, the Roman goddess of growth . ¢= June - after the Roman tribe of Junius, and connected with Juno, queen of the gods fA crescent Moon gibbous Moon () July - after Julius Caesar, who named it after himself ~ (waning)· (waxing) August - after Augustus Caesar; who wanted his own month too - and stole a day from February so that his month was 31 days as well September - after Latin septem, 'seven', because The outer ring of sketches shows the Moon as it appears in the sky. the old Roman year began in March October - after Latin octo,'eight' See 'An Early Start to Nature', page 60, for ways of plotting the November - after Latin novem,'nine' Moon through the month. December - after Latin decem, 'ten' E The Egyptians The ancient Egyptians had a calendar of 12 months, each of 30 days, with 5 supplementary days added at the end of each year. Using this method a quarter of a day is lost every year. This year is called 'vague' because with the passage of time the lost quarter days E S w E S w E S w accumulate and the year starts earlier and earlier. early 21 early The Muslim calendar still wanders in this way. morni~ 0···.-(; morningck3-·G morning The Israelites -r. sunrise ~orning / sunrise The ancient Jewish calendar is based on the Moon. The year has U 21 ~ 12 months, each of 29 or 30 days, with the insertion of a 13th month 7 times during each 19 year period. 'tne year 65 The natural year is the time taken for the Earth to pass around A world calendar the Sun: 365 days, 5 hours, 48 minutes, 46 seconds. In order to make dates easier to deal with it has been suggested that we have a world calendar. Birthdays and other events would always fallon the same day of the week and we would not need to reprint the calendar. January, April, July and January I October have 31 days. ~~~~~~~~~~Fe:b:ru~a~r~ __ ~~ --~------March -l r SMTWTFS All other months have SMTWTFS -- SMTWTFS 30 days. This makes a 123 456 7 total of 364 days. 8 9 10 11 12 13 14 1 2 3 4 15 16 17 18 192021 5 6 7 8 9 10 11 1 2 12 13 14 15 16 17 18 3 4 5 6 7 8 9 22 23 24 25 2627 28 The 365th day, called 293031 192021 22232425 10 11 12 13 141516 26 27 28 29 30 17 18 19 20 21 22 23 ~Moon Worlds day , comes at \ii!:I =---~:;;-----+~~:;:April ": 12~4~2~5226627 2829 30 the end of December; [ ~M~a~y~__ June it would be a SMTWTFS~~~;:~~~-r~__ ~~==~ r SMTWTFS ------universal holiday. SMTWTFS 123 456 7 8 9 10 11 12 13 14 1 2 3 4 15 16 17 18 192021' 5 6 7 8 9 10 11 1 2 In leap years an extra 12 13 14 15 16 17 18 3 4 5 6 7 8 9 22 23 24 25 26 27 28 192021 22232425 1011 12 13 1415 16 day is added at the 293031 It is an awkward unit of time, and a calendar has evolved where end of June. '-- 2627 28 29 30 17 18 19 2021 22 23 ----~~--"---+--~~;;_--12~4~2~5~26~2'28297 30 the days of the year are divided between the months and any [_ July August _ [ll odd time left over is mopped up in leap years. Many of us resort There are four ~~~~~~+~~~~~--~~~S~e~Pt~emberSMTWTFS -- r SMTWTFS ---- to the old rhyme to help us remember how many days in each quarters to the year, SMTWTFS beginning on thefirst 123 456 7 month. 8 910 11 121314 5 1 2 3 4 ' of January. Each 15 16 17 18 1920 21 6 7 8 9 10 11 3 4 1 2 Thirty days hath September, quarter starts on a :::~:: 25262728 ;: ;~;: ;~ ;~;;;: 10 11 1~ 1~ 1; 1: 1: April, June and November, Sunday and ends on f-- I 2627 28 2930 ,17 18 19 2021 22 23 I' October I 24 25 26 27 28 29 30 All the rest have thirty-one a Saturday. [ November I D -- - Excepting February alone SMT W ecember Which hath but twenty-eight days clear, What do children TFS S~TWTFS _ SMTWTFS And twenty-nine in each leap year. think of such a 1234567 8 9 10 11 1213 14 123 4 1 2 calendar? 15 16 17 18 192021 5 6 7 8 9 10 11 3456789 22 23 24 25 26 27 28 12 13 14 15 16 17 18 Make a survey of special dates. Collect iriformationjrom the 10 11 12 13 1415 16 L9 30 31 192021 222324 25 children. Look up diaries. Special astronomical I 26 27 28 29 30 17 18 19 2021 22 23 dates I 24 25 26 27 28 29 30 ----J Blrthd~s HolicJ..o.ys Naiional: Festivals . . Children could look up the dates when the length of day and night Mnlversanes are equal, the equinox. They could also find out the date for the longest day (Summer solstice), Midsummer's Day, and the shortest Xrno..sDa:J g~fo.WRe.s day (Winter solstice). Thcmt<5gtVtn.9 The spring (or vemal) equinox - March 21 or 22 The longest day, Summer solstice - June 21 or 22 The autumnal equinox - September 21 or 22, Put everything in date order. The shortest day, Winter solstice - December 21 or 22 66 The Moon Children can look at the Moon through binoculars. It is an exciting thing to do because it reveals fine detail. Resting arms on a wall helps keep the binoculars as still as possible. The mainfeatures are the rolling plains, the maria, which usually appear darker than surrounding areas; the craters; and the mountain ranges. There are a number of source books that have photographs of the Moon, including the side away from the Earth. These make good material to supplement actual Moon watching. The craters are named after famous astronomers and scientists, like Plato, Archimedes and Copernicus. Mountain ranges are named after ranges on Earth, for example Alps, Appenines and Carpathian Mountains. Maria havefanciful names like Mare Humboldtianum, Mare Humorum and Mare Serenitatis. The Moon 67 Tides Why tides vary The Moon orbits the Earth at an average distance oJ384,400 km. The Sun also exerts a gravitational pull on the Earth. If the Sun The nearer a mass is to the Moon the more strongly it is pulled by and Moon are in line, the high tides are higher; these are called the mass oj the Moon. Thus it is that we have the rise and Jall oj 'spring tides'. If the Sun and Moon are at 900 to each other, the the tides twice a day. gravitationalJorces work against each other and we have lower 'neap tides'. The ocean shown at A in the diagram is nearer to the Moon than the solid sphere oj the Earth and it is thereJore pulled more new Moon first quarter strongly towards the Moon. This results in a large bulge Jonning in the ocean. At point B in the diagram the ocean is Jarther from the Moon than the solid part oj the Earth. Again this results in a bulge in the ocean. The bulges stay in line with the Moon. low tide last quarter B A However, because the Earth is spinning the bulges move around the Earth in the opposite direction. When a"bulge reaches a place, spring tides neap tides that place has a high tide. Since there are two bulges, there are two high tides and two low tides each day. Schools in coastal areas can check the tides against published tide tables, and examine the tables to see how the tides vary through the year. -r;de TnblIlS, -_...... • ~.•~.~...... 68' Timers The key concept in any study of time with A marble rolling down a slope children is developing the idea of the duration of events, and measuring such events. Inventing How many: docks to measure events is not only fun but takes pin-men children into problem solving and into technology. words crosses The timing problem can be an open one, for can you make before the example: marble runs its course? 'Choose any time between 5 and 50 seconds and make as accurate a timer as you can to measure Try making the route so that time. Use any of these materials, plus water that the marble takes: if you need, it.' 10 seconds 15 seconds 20 seconds to traverse it. softwood Experiment with the variables 1 The height ,of the slope Try it on a larger scale with a table 2 The size of the ball tilted on books. Use balls made from Plasticine • 3 The heaviness of the balls • Make sure the size is constant. wood ball bearing marble :c ;- 'An Early Start to Science', page 25,features some simple water, sand and candle docks. Here are more suggestions for timers. Timers 69 The pendulum Children uiill find. that th.eonly effective variable A water alarm is the length oJthe string. The pendulum is a common timing device. This.consists oj a cork or polystyrene float Plot a graph oj time against length by gradually covered in aluminium kitchenJoil, which rises in a The mainJactors to investigate in time oj swing oj increasing the length oj the pendulum to a good container to make a connection across two bare a pendulum are: 10 to 20 cm over 1 metre. wires and thus complete an electric circuit. This causes a buzzer to sound or a bulb to light. • the size oj the bob hole to let air in • the size oJthe swing ii.e. big swings/little swings) length- • whether the pendulum is given a push em • the lengt~ oj the string TImeof 20 swi ng5 Read off from the graph the length oj a seconds pendulum - that is, a pendulum that swings frotti right to left inI second. (It is approximaielu 1 metre long.) Alarm clocks Here are some candle alarms. Investigate each in tum by timing 20 swings oJ· the pendulum. cut end Leave the length oj the string until last. of a plastic drinks bottle, float covered in kitchen foil The trick is to control the rare at which water flows into the container so that it completes the circuit in afixed time. Water can be made to run in from a plastic bottle as long as there is a hole in the other end to let the air in. A subsidiary technical problem is to suspend the bottle. A damp will do, but good technology could In each case theJalling pin or nail will make a comefrom. making a standfrom wood or noise. Meccano. 70 The planets The name planet comesfrom the Greek uiord for Sun. The orbits oj the planets are shown in the Neptune's orbit for aJew Earth years - the last 'wanderer', because oj the way the planets move illustration below. Pluto is usually the most time this happened was at the end of the 1980s. slowly across the background oj stars. In our distant planet from the Sun, but its orbit is The planets do not give off any light oj their own. solar system there are nine planets orbiting the eccentric and every so often it crosses inside We can see them because they are lit by the Sun. Draw the planets in 2D to scale on paper. Make the planets in 3D as popter-mache objects. Hang themjrom the ceiling when decorated. Diameters Planet Diameter Mercury 4,878 km Venus 12,103 km Earth 12,756 km Mars 6,794 km Jupiter 142,800 km Mercury! Saturn 20,660 km The Sun's diameter is almost 10 times Uranus 51,400 km that of Jupiter, so it is too large to model Neptune 49,400 km to scale. Pluto 2,280 km Diameters of the planets compared to Earth (approx) circle of card Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto Uranus has a veryJaint ring. In fact Neptune and 0.4 1 1 0.5 11 9.5 4.0 3.9 0.2 Jupiter also have almost invisible rings, but there is no point in modelling these; 72 The lanets Distances Approximate distance of the planets from the Sun in millions of km The distances between the planets are vast. Some idea of the relative distances can be gained Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto by measuring them to scale outdoors. A scale of 1 em to represent 1 million km is suitable. It can 58 108 150 .228 779 1427 2869 4497 5900 then be seen that the planets near the Sun are relatively dose together, while those farther away are a considerable distance apart. To this scale, Sun Pluto, the planet furthest from the Sun, will be some 59 mfrom the person representing the Sun. ~NePtune Pluto Saturn Uranus Painted scale pictures of the planets could be held up at each distance - as could scaled 3D models. But you won't be able to make the model of the Sun to scale, as it would be much too large. ,·The planets 73 Library work Planet Rotation period Time to circle the Sun (Earth years) Astronomers over the centuries have found out a great deal about the planets. Some are solid, Mercury 59 days 0.24 some are swirling masses of gas and liquid held Venus 243 days 12 hours 0.62 down by gravity on to a rocky core. Some have moons of their own, some are so large that they Earth 23 hours 56 minutes 1.00 exert a very big gravitational pull. The Voyager Mars 24 hours 37 minutes 1.88 ' probes of recent time have suddenly added an immense amount to our knowledge of the Jupiter 9 hours 55 minutes 11.86 planets. There is muchfor children to research Saturn 10 hours 14 minutes 29.46 in library books on the subject. Uranus 10 hours 48 minutes 84.02 Neptune 15 hours 48 minutes 164.80 Pluto 5 days 9 hours 248.00 You would get lots of birthdays on Mercury butfew in a lifetime on Satum. Making big numbers clearer The sizes and distances expressed in dealing with objects in space are so large that we often express them in a mathematical notation. For example, 137,520 is written as 1.3752 x 105. Try this for the data on the planets in the table below. Thefirst example is done. Planet Distance from Distance in Diameter of Diameter in Sun (km) mathematical.netation planet (km) mathematical notation Mercury 57,900,000 5.79 x 107 4,878 4.878 x 103 Venus 108,200,000 12,103 Earth 149,600,000 12,756 Mars 227,900,000 6,794 Jupiter 778,900,000 142,800 Saturn 1,427,000,000 120,660 Uranus 2,869,000,000 51,400 Neptune 4,496,700,000 49,400 Pluto 5,900,000,000 2,280 The stars are in reality suns. Each is an The stars appear to revolve anticlockwise around Using star maps extremely hot mass oJglowing gas. They appear the Pole Star. This is caused by the Earth faint because they are soJar away. Some stars spinning beneath the heavens. 'An Early Start to Star guides such as those produced by George are bigger than others. Some stars are hotter than Nature', page 61, gives detailsJor making a star Philip and Son Ltd are idealJor identifying others. The hotter the star, the brighter it is. Many clock based on this phenomenon. It also suggests constellations and individual star names are derived Jrom Arabic, since it was some activities to carry out on constellations. stars. It is best to orientate Arabic culture that continued the pursuit oj yourself so that scientific knowledge during the dark days oj the youJace due north Middle Ages in Europe when science was south before virtually Jorgotten. you begin star spotting. Star rotation Put a screw eye into the end oj a 1-:5 m rod. Stand the rod in a 3 litre plastic bottle filled with soil or sand which acts as a support. Use a star map to identify a constellation and look through the screw eye in order to line up one oj the stars in that constellation with the top oj a lamp post, or a tree, or a rooftop. Look Jor the star at 10 minute intervals. Does it appear to move? Check other stars. Check the Pole Star! -l> Z soil or sand in c:: 3 litre plastic bottle » -<= The stars 75 Brightness How far away? Each step on the scale is 2.5 times less bright than the one before. A magnitude 1 star is thus Star brightness depends on how big the star is, Just move the tube, with one pinprick of light, 100 times brighter than a magnitude 6 star. how hot it is, and howfar away it is. farther and farther away from watching children. Telescopes will show up much fainter stars with magnitudes far beyond 6. How big? Try judging this scale against some easily spotted Use the cardboard kitchen ron tube constellations. This is the scale for the stars of tube from a kitchen or Orion, which dominates the winter sky. toilet roll. Cover one end with black paper. Prick holes oj various sizes in the paper. Put a lit torch into the tube and stand it on a table. Stand well away and advance toward the dots of light until you can just see each one. Record the distance. 'Star Size' Dista.nc.e seen Pinhole Measuring brightness Compass needle hole. Astronomers have a scale for measuring Biropoi.nt hole brightness. Knitbn9 needle hoLe. very bright very faint 1 How hot? 3 4 5 6 This time use two torches of equal power. one 0 shaded with tissue paper. the other left as 00 o normal. The black paper covering each tube 06 should bear an equal sized hole. A star with a magnitude of 1 is very bright. Even brighter stars have magnitudes down to 0 and below - the brightest star, Sirius, has a Betelgeuse is.a reddish colour. Its temperature is magnitude of -1.58. 3000K. The faintest stars we can see with the naked eye Rigel is bluish white and very hot. Its temperature have a magnitude of 6. is 15,000 K. 76 The Shuttle Trace the two templates shown below on to card to make ajlying model of the Shuttle. Cut them out. Score the dotted lines. Cut where shown. Join the main wings to thefuselage by slotting them into place. Strengthen with tape above and below. .3 engines inner -r-r-r-i-r--r-r-: elevon payload bay cut ~ ..- ---.I~--- cut slot- r----'---~------c=:======:; ~thickness of the card Testjly. Ijnecessary, weight the nose withpaperdips or a small piece oj Plasticine to get a good balance. For ajlat glide tip the outer elevons up. For a right tum tip the outer eleoons up, the inner left elevon down and the inner right elevon up. Twist the rudder to the right. This is the Saturn V three stage A model rocket 8 Make a launch pad for the rocket used to send the Apollo rocket. spacecraft to the Moon between 1969 and 1972. spacecraft 1 Make a nose conefrom a half 4 Make three fins. circle of card. third cm~Z~ score stage F' cut /' . 7 cm radius 5 Bend a paper clip to make a 'launch hook'. 2 Push Plasticine as second a nose weight into stage the cone. C ::i) 6 Push the 'launch hook' into the body. Pinch it tight. Secure it inside and out with masking tape. 3 Stick the nose cone to a kitchen paper towel roll body. first 9. Record your results. stage 7 Stick the three fins by their flaps to the body. Angl1l. T, me NES Arnold Ltd Ludlow Hill Road West BTidgford Nottingham NG26HD Telephone: 0602 452204 Griffin & George Ltd Bishops Meadow Road Loughborough Leicesters hire, LEI1 ORG Telephone: 0509 233344 Philip Harris Ltd Lynn Lane Shenstone Staffordshire, WS14 OEE Telephone: 0543 480077 Berol Lui Oldmedow Road Kings Lynn Norfolk, PE30 4JR Telephone: 0553. 761211 RS Components PO Box 427, 13-17 Epworth Street London, EC2P 2HA Telephone: 071-253-1222 A clinometer 55 E gnomon, sundial 52-54 longest day 65 planets 72 acidity 11 clocks 68, 69 Earth 4, 38, 50, 56, 57, graphs 13,49, 51, 58, 60, longitude 63 stars 74,75 acid rain 48 clouds 18, 38 62-67, 70-74 69 compost 14 aeration 11 combustion 46 Earth's grasses 49 M displacement 27 air 24, 38-49 compass 51 axis 52, 56, 57 gravel 8, 10, 16 magnitude, star 75 floating 27 aircraft 44,45 compost 12-14 rotation 50 gravitational pull 67, 73 making things that work tdenttfytng animals 37 air pressure 38-44 computer programs 31 east 51, 52, 63 greenhouse effect 47 aircraft 45 identifying plants 31 alarm clock 69 coniferous trees 29 energy 48,58,60 Greenwich 63 alarm clocks 69 pollen count 49 algae 28,30 constellations 74, 75 Equator 4, 52, 57 grit 16 marble run 68 shadows 50,51 alkali 11 continent 4 equinox 57,65 growing shadow clock 51 soil sampling 8, 10 amphibians 34, 36, 37 core 4 erosion 12 crystals 6-7 solar panel 61. solar heating 61 animals cotyledon 30 Europe 47 plants 13, 31 submarine 27 sundials 53 single celled 32, 36 crops 47 evaporation 6, 18, 19, 38 Guericke 43 sundial 53 surface tension 22 spiny skinned 32,36 crust 4 evergreen trees 30 gymnosperms 30 mammals 35-37 oxygen 46 two layered 32, 36 crustaceans 33,36 experiments mantle 4 ozone 38,47 with backbones 34-36 crystals 6, 7 air 39,40, 41,44, 46 H Mars 4, 70-73 with jointed limbs 33, 36 crystal garden 7 candle 46 habit 37 marsupials 35 P without backbones 32,33, cube 7 colour 11 hard water 19 mass 9, 24, 25 parasites 30 36,37 growing crystals 6-7 hay fever 49 Mercury 4,70-73 Pascal 43 arachnids 33,36 heat 9, 59-61 hemisphere 43 mercury 42,43 pebbles 27 Archimedes principle 24, 25 D light 59 hieroglyphs 62 methane 47 pendulum 69 Asteroids 4 data 49 paper 40,44,45 histogram 51 microbes 15, 16 percentages 9 astronomers 73,75 dates 65 shadow 50-54 humidity 49 Midsummer's day 65 photosynthesis 30 atmosphere 4,38,40,46,47, day 56,57,62,63,67 soil 8-15 humus 8, 9, 14 mist 18 pH test 11 49 days of week 62 star 74-75 hydrosphere 4 molluscs 32, 36 planet 4,70-73 aurora borealis 38 decay 14, 15 sundial 53, 54 monocotyledons 29, 30 plane table 55 autumn 56, 57 deciduous trees 30 timing 46, 51, 53, 54, 68, I month 64 plants 28-31, 48 density 24,25 69 Ice Age 5 Moon 64-67 plants with flowers 29, 30 design projects water 41 inosphere 38 moons 73 plants without flowers 28-30 B aircraft 45 indicator 11 mosses 28,31 Plimsoll mark 25 bacteria 14, 16 alarm clock 69 F industry 47 moulds 15 Pluto 4, 70-73 . barometer frieze 48, 56 farming 47 insectivores 35 mountain 43, 66 poem 50,65 aneroid 42 geometric shapes 7 ferns 28,30 insects 22, '33, 36, 49 polar caps 47 mercury 42, 43 pendulum 69 fertility 13 insulator 38 N Pole Star 74 bats 35 planets 70-73 fertilizer 13 invertebrate 37 natural gas 47 pollen 49 binocular microscope 6 poster 47 filter 38 iron ships 25 neap tides 67 pollution 48 binoculars 58, 66 Saturn V 77 filtration 19 Neptune 4,70-73 pond animals 22 birds 34, 36, 37 seasons model 57 fish 34, 36, 37 J nets 7 porosity 10 brightness, star 75 sewage works 17 flatworms 32, 36 Jupiter 4,70-73 New York 63 pressure 24,40,41 British Isles 5 space shuttle 76 flight 44, 45 night 57, 62, 63 primates 35 burning 46 sundial 53, 54 floating 24-27 K nitrogen 46 prime meridian 63 timers 68, 69 flooding 47 keys 31 north 51 protozoa 32,36 water alarm 69 flower 29 North America 47 pump C water erosion 12 flowering plants 49 L North Pole 52, 53, 57 air 43 calcite 7 diaries 65 forests 47 lagomorphs 35 North Star 52 bicycle 42 calendar 64, 65 dicotyledons 29, 31 fossil fuels 47 lakes 18,48 Northern Hemisphere 57 candle alarm 69 displacement 25, 27 fungi 15,28,30 latitude 38 nuclear fusion 58 Q carbon dioxide 47 disposal of material 15 leaf 30 quartz 7 carnivores 35, 36 drag 44 G leap year 65 0 CFCs 47 drains 16, 17 Galileo 42 lichens 28,30 ocean 4, 18, 38, 67 R chlorophyll 30 drawing gas 18, 73 lift 44 orbit 56, 67, 70 rain 18, 38, 48, 49 classification and sorting animals 37 geology 5 light 70 Orion 75 recording data animals 36-37 shadows 51 geometric shapes 7 lignum vitae 26 outdoor activities burning 46 plants 30, 31 surface tension 37 glider 45 lime 11, 14, 48 astronomy computer base 31 clay 8, 10, 11, 13 drought 47 globe 57 liverworts 28, 30 moon 66 (continued) dates 65 spacecraft 76. 77 drinking 48 density 24 spring 49. 56. 57 erosion 12 floating 26. 27 spring tides 67 level 21 greenhouse effect 47 star 58. 70. 74. 75 pressure 20.41 mould culture 15 steam 18 vapour 18.38.46 planets 73 stopwatch 68 waste disposal 16 seasons 56 stratosphere 38 weather 38. 49 soil content 9 submarine 27 weathering 5 sorting animals 37 summer 56. 57 weighing 9. 10 sorting plants 31 Sun 38.47.50.51.55-59.62. weight 27.40 spacecraft flight 77 63. 70-74 west 51.52.63 stars 75 sundial 52. 53 wind 18.49 surface tension 23 sunrise 58 erosion 12 temperature 60.61 sunset 58 wings 44.45 time and place 63 sunspots 58 winter 38. 56. 57 timing 69 surface tension 22-24.26 World calendar 65 reptiles 34. 36 symbiosis 30 worms 32.36 rivers 18 rock 5.6.73 T y rock salt 7 telescope 58 year 64.65 Royal Observatory 63 temperature 38. 49. 57. 60. run off 12 61 rusting 46 thermometer 59.61 tides 62.67 S time 50.51.53.54.63.65 Salt 6 timekeeping 62. 63 sand 10. 12. 13. 16. 19. 26 timers 68. 69 saprophytes 15.30 time zone 63 Saturn 4. 70-73 topsoil 12 sea 18.47 Torricelli 42 sea level 47 toys to make. seasons 56-57 aircraft 44.45 sedimentation tank 16 spacecraft 76. 77 seeds 13.30 submarine 27 segmented worms 32. 36 trees 49 sewage 16 tropopause 38.47 shadow 50-53 troposphere 38 shadow clock 53 turf 12 shortest day 65 shrinkage 13 U shrubs 30 ultraviolet 47 shuttle 76 ungulates 35 silt 10 upthrust 25 sinking 24-27 Uranus 4.70-73 sky 50.51 sludge 16 V snow 18. 38 vacuum 42 soil 5. 8-11. 14. 15. 48 Venus 4. 70-73 solar heating 60. 61 volume 27. 46 solar system 4.58.70 Voyager probe 73 solvent 19 sorting 14. 31. 37 W south 51 water 9 South Pole 57 alarm 69 space 64 cycle 18.38