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Term pack

Class 7 Science

Name: ________________________

Skills in this pack

  • Acidic, basic and neutral substances
  • Circuits and their components
  • Metals and non-metals
  • Physical and chemical changes
  • Adolescence: growth and change
  • Heat transfer in nature
  • Measuring time
  • Speed and motion
  • Life processes in animals
  • Life processes in plants
  • Light, shadows and reflection
  • The Earth, the Moon and the Sun

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Class 7 Science · 1 of 12

Acidic, basic and neutral substances

Sort everyday substances as acidic, basic or neutral, read what each natural indicator is telling you, and use neutralisation to explain an ant bite and a sour field.

  1. 1.An acid solution and a base solution are mixed in the right amounts and the result is neither acidic nor basic. What is this reaction called?

  2. 2.Red rose extract has been added to each of these three test tubes. Tap the tube holding a basic solution.

    Write the number of the part.

    123

  3. 3.Manya is blindfolded and handed two solutions to tell apart. Which kind of indicator could she still use?

    • a) Red rose extract, because it is a strong colour
    • b) Turmeric paper, because turmeric is a familiar spice
    • c) An olfactory indicator, whose smell changes
    • d) Litmus paper, because the strips feel different

  4. 4.Put the steps of making a red rose indicator back into the order the chapter gives them.

    • Crush the petals with a mortar and pestle
    • Wash the fallen rose petals in water
    • Pour hot water over the crushed petals and cover the tumbler
    • Filter off the coloured liquid and keep it as the extract

  5. 5.Match each problem to the treatment the chapter gives for it.

    • Soil that is too acidic
    • Soil that is basic
    • Acidic factory waste
    • treated with manure and composted leaves
    • treated with a basic substance before release
    • treated with lime

  6. 6.A substance that shows one colour in an acid and a different colour in a base has a two-word name in this chapter. What is it?

  7. 7.Each of these was tested with blue and red litmus paper. Sort them by the nature the papers reported.

    Groups: Acidic · Basic · Neutral

    • Vinegar
    • Lime water
    • Salt solution
    • Soap solution
    • Tamarind water
    • Washing powder solution
    • Lemon juice
    • Sugar solution

  8. 8.A drop of an unknown liquid is put on turmeric paper and the yellow does not change. Which two possibilities are still open?

    • a) Nothing is open — turmeric paper settles it
    • b) It is acidic, or it is neutral
    • c) It is acidic, or it is basic
    • d) It is basic, or it is neutral

Acidic, basic and neutral substances · Class 7 Science · www.arenapublications.com/learn

Class 7 Science · 2 of 12

Circuits and their components

Name the parts of a torch circuit and what each does, read a circuit diagram's symbols, tell a conductor from an insulator, and say when a lamp glows and when it does not.

Before you start

Take apart an incandescent torch lamp and look at what makes the light.

1234
  1. 1. Glass bulb
  2. 2. Filament
  3. 3. Metal case
  4. 4. Metal tip

The filament is the thin wire that gets hot and glows. The metal case and the metal tip are the lamp's two terminals, kept apart so they cannot touch. An LED lamp has no filament inside it — it makes light a different way.

  1. 1.An incandescent lamp is taken out of a circuit and put back with its two terminals the other way round. What happens?

    • a) It stays dark, because current can pass through it in one direction
    • b) It glows more brightly, because the current now runs the natural way
    • c) It glows dimly, because half the current is turned back
    • d) It glows just as before, because the circuit is still complete

  2. 2.Two or more electric cells joined cap-to-disc, so the positive terminal of one meets the negative terminal of the next, are together called what?

  3. 3.Match each part of a torch circuit to the job it does.

    • Electric cell
    • Switch
    • Filament
    • completes or breaks the circuit
    • a portable source of electrical energy
    • gets hot and glows to give light

  4. 4.A drawing that stands in for a real circuit, made out of the agreed symbols rather than pictures, has a two-word name. What is it?

  5. 5.Silver, copper and gold are the three best conductors. Why is the metal inside an electric wire usually copper?

    • a) Copper is easier to draw into a thin wire than any other metal
    • b) Copper costs less and there is plenty of it, and it conducts nearly as well
    • c) Copper is the one metal that conducts electricity
    • d) Silver and gold are insulators

  6. 6.Follow the current round a working torch circuit, starting at the positive terminal of the cell.

    • The positive terminal of the cell
    • The negative terminal of the cell
    • The filament of the lamp
    • The switch, closed to ON

  7. 7.In the symbol for an electric cell, one line is drawn long and one short. What does the long line stand for?

    • a) The negative terminal
    • b) The positive terminal
    • c) The amount of energy left in the cell
    • d) The wire leaving the cell

  8. 8.A torch is slid to OFF. What is true of its circuit while it sits like that?

    • a) It is closed, and the current is stored inside the cell
    • b) It is open, and the current takes a shorter path instead
    • c) It is closed, but the current is too weak to light the lamp
    • d) It is open — a gap is left that the current cannot cross

Circuits and their components · Class 7 Science · www.arenapublications.com/learn

Class 7 Science · 3 of 12

Metals and non-metals

Tell metals from non-metals by malleability, ductility, sonority and conduction, say what rusting and corrosion need, and give the nature of a metal oxide and a non-metal oxide.

  1. 1.Heat passing from one point of a spoon along to another point has a one-word name in this chapter. What is it?

  2. 2.An iron gate left out through a wet season grows a brown flaky deposit. What is that deposit called?

  3. 3.A hammer is brought down on a lump of coal and it shatters. What is the word for behaving that way?

    • a) Malleable
    • b) Sonorous
    • c) Brittle
    • d) Ductile

  4. 4.Match each non-metal to the everyday job the chapter gives it.

    • Nitrogen
    • Chlorine
    • Iodine
    • goes into making fertilisers
    • put on a wound as an antiseptic
    • used to purify water

  5. 5.Match each property to what a material showing it can do.

    • Malleability
    • Ductility
    • Sonority
    • can be beaten into thin sheets
    • gives a ringing sound when struck
    • can be drawn into wires

  6. 6.Why does the chapter say that wood, glass and plastic are neither metals nor non-metals?

    • a) Because they float in water, and metals and non-metals sink
    • b) Because those two names are for elements, and these materials are not elements
    • c) Because they are neither hard nor soft enough to be tested
    • d) Because they are made in factories rather than dug out of the ground

  7. 7.Copper going green and silver going black are the same kind of slow damage that a brown deposit does to iron. What is the general name for a metal surface being eaten away like this by air, water or other substances?

  8. 8.Sort each of these elements into its family.

    Groups: Metal · Non-metal

    • Oxygen
    • Carbon
    • Aluminium
    • Sulfur
    • Magnesium
    • Copper
    • Iron
    • Nitrogen

Metals and non-metals · Class 7 Science · www.arenapublications.com/learn

Class 7 Science · 4 of 12

Physical and chemical changes

Decide whether a change has made a new substance or merely rearranged an old one, say what combustion needs, and name the slow changes that turn rock into soil.

Before you start

Look closely at a burning candle. Two different kinds of change are going on at once.

1234
  1. 1. The flame
  2. 2. The wick
  3. 3. The pool of melted wax
  4. 4. The solid wax of the candle

The wax melting into a pool, being drawn up the wick and turning to vapour are physical changes — it is still wax. Inside the flame, that vapour burns and becomes something else. That part is a chemical change.

  1. 1.Sand that a river carried settles on the riverbed, and over thousands of years it becomes rock. What does the chapter say about undoing changes like that?

    • a) They can be reversed by grinding the rock back to sand
    • b) They cannot be reversed
    • c) They can be reversed, but just in a laboratory
    • d) They reverse themselves each rainy season

  2. 2.Blowing exhaled air through lime water turns it milky. What does that milkiness tell you was in the exhaled air?

    • a) Carbon dioxide
    • b) Oxygen
    • c) Water vapour
    • d) Nitrogen

  3. 3.Match each process to what it does.

    • Combustion
    • Weathering
    • Erosion
    • breaks rock down where it lies, and eventually makes soil
    • a substance reacts with oxygen, giving out heat or light
    • carries broken rock away by wind or flowing water

  4. 4.Which statement describes a physical change?

    • a) The change is impossible to reverse
    • b) A substance with different properties is formed
    • c) The state of a substance may change, and no new substance is formed
    • d) A chemical reaction takes place and gives out heat

  5. 5.A different question about the same changes: sort each one by whether you can get back what you started with.

    Groups: Can be reversed · Cannot be reversed

    • Chopping vegetables
    • Boiling water
    • Making popcorn from corn
    • Melting an ice cube

  6. 6.Water is boiled in an open pan and the steam is caught and cooled back into water. Which pair of words fits this change?

    • a) Chemical, and it can be reversed
    • b) Physical, and it can be reversed
    • c) Chemical, and it cannot be reversed
    • d) Physical, and it cannot be reversed

  7. 7.Sort each change by whether a new substance was formed.

    Groups: Physical change · Chemical change

    • Adding baking soda to vinegar
    • Cooking food
    • Burning a magnesium ribbon
    • Folding paper into a shape
    • Crushing chalk into powder
    • Melting an ice cube
    • Rusting of an iron nail

  8. 8.Someone's clothes catch fire and a woollen blanket is wrapped around them. Why does that put the fire out?

    • a) It soaks up the fuel that is feeding the flames
    • b) It cuts off the supply of air, so the burning has no oxygen
    • c) It reflects the heat back onto the fire and smothers it with light
    • d) It cools the clothes below their ignition temperature at once

Physical and chemical changes · Class 7 Science · www.arenapublications.com/learn

Class 7 Science · 5 of 12

Adolescence: growth and change

Place adolescence among the stages of life, name the changes it brings and what drives them, and say what looks after health at this age.

Before you start

Slide along this line of ages and see where the chapter puts adolescence.

0510152025

Adolescence generally begins around 10 and usually runs to 19. Before about 10 to 12, most of what changes in a body is height and weight; the rest begins after that. These are the chapter's general ages, not a timetable anyone has to keep to.

  1. 1.A girl's menstrual cycle comes round once in 33 days. What does the chapter say about that?

    • a) Cycles longer than 30 days stop after a year
    • b) A cycle has to be 28 days, so this one is a sign of illness
    • c) Many healthy girls have cycles anywhere from 21 to 35 days
    • d) The length of a cycle has nothing to do with health

  2. 2.What is the name for the stage in which a child's body changes, inside and out, into an adult body capable of reproduction?

  3. 3.Sort each of these by what the chapter says it does to health during adolescence.

    Groups: Looks after health in adolescence · Harms health in adolescence

    • Eating a balanced diet
    • Drinking alcohol
    • Chewing tobacco
    • Taking regular exercise
    • Keeping the body clean

  4. 4.Why does an adolescent boy's voice often sound hoarse for a while?

    • a) His throat is short of water
    • b) His voice box is growing
    • c) His lungs have grown faster than his throat
    • d) He is speaking more loudly than he used to

  5. 5.What does it mean to say that a substance such as tobacco or alcohol is addictive?

    • a) It changes a person's mood while it is being taken
    • b) Once a person starts taking it, they develop a strong urge to take it again and again
    • c) It damages the lungs the very first time it is taken
    • d) It is against the law to sell it

  6. 6.Match each nutrient to what the chapter says it does for a growing body.

    • Calcium
    • Proteins
    • Iron
    • help growth, strength and energy
    • helps blood to form
    • helps bones grow well

  7. 7.Chemicals made in the body drive most of the changes of adolescence and are released on signals from the brain. What are they called?

  8. 8.The chapter gives an age around which adolescence generally begins. Which age is it?

    Mark the line with an X.

    012345678910111213141516171819202122232425

Adolescence: growth and change · Class 7 Science · www.arenapublications.com/learn

Class 7 Science · 6 of 12

Heat transfer in nature

Tell conduction, convection and radiation apart by what the particles do, explain land and sea breezes, and follow water from the sea to an aquifer.

Before you start

Four pins are stuck along a metal strip with wax, and one end of the strip is heated. Here is the strip, pin by pin.

1234
  1. 1. Pin I
  2. 2. Pin II
  3. 3. Pin III
  4. 4. Pin IV

The heat travels along the strip from the heated end towards the cold one, melting each blob of wax as it arrives. Pin I sits nearest the flame and Pin IV farthest away, so the pins drop one after another in that order. The strip itself has not moved anywhere — just the heat has.

  1. 1.Groundwater levels in many towns are falling. Which pair of causes does the chapter give?

    • a) Too much rainwater harvesting, and too many recharge pits
    • b) Rainfall stopping altogether, and rivers changing course
    • c) Aquifers turning to solid rock, and wells being dug too shallow
    • d) Heavy extraction for a growing population, and concrete surfaces that leave less room for water to soak in

  2. 2.Match each way of transferring heat to what the particles are doing.

    • Conduction
    • Convection
    • Radiation
    • the heated particles themselves move, carrying the heat
    • heat passes along, and the particles stay where they are
    • heat crosses with no medium to carry it

  3. 3.The same amount of water is poured through one bottle of clay, one of sand and one of gravel. Through which does it come out fastest, and why?

    • a) Clay, because its particles are the smallest and pack loosely
    • b) They finish together, because the same water was poured into each
    • c) Sand, because it is the driest of the three
    • d) Gravel, because the spaces between its particles are the widest

  4. 4.Convection in a beaker turns round and round with no true beginning, so start from the step where water at the bottom is heated by the flame and put the rest in order.

    • Cooler, heavier water sinks down the sides to take its place
    • The heated water expands and becomes lighter
    • Water at the bottom is heated by the flame
    • That lighter water rises up through the middle

  5. 5.Which of the three ways of transferring heat can cross a space with nothing in it?

    • a) Conduction
    • b) Conduction and convection both
    • c) Convection
    • d) Radiation

  6. 6.An underground layer of sediment and rock that holds water in its pore spaces, and that a bore well is drilled into, has a name. What is it?

  7. 7.Sort each material by how readily it lets heat pass through.

    Groups: Good conductor of heat · Poor conductor of heat

    • Aluminium
    • Steel
    • Wood
    • Glass
    • Air
    • Clay

  8. 8.Why is light-coloured clothing more comfortable in summer?

    • a) It is made of thinner cloth than dark clothing is
    • b) It reflects most of the heat falling on it, while dark surfaces absorb more
    • c) It lets sweat evaporate faster than dark cloth does
    • d) It conducts heat away from the body faster than dark cloth

Heat transfer in nature · Class 7 Science · www.arenapublications.com/learn

Class 7 Science · 7 of 12

Measuring time

Say how old clocks kept time, find a pendulum's time period from a count of oscillations, and convert between the second, the minute and the hour.

Before you start

The parts of a simple pendulum, and where the bob reaches at one extreme.

1234
  1. 1. The support
  2. 2. The thread
  3. 3. The bob
  4. 4. One extreme

The dark bob hangs at the mean position, straight below the support. The pale one shows where it reaches at one extreme; there is a matching extreme on the other side. One oscillation is mean, extreme, across to the other extreme, back to mean.

  1. 1.What does a quartz clock count to keep time?

    • a) The swings of a very short pendulum
    • b) Drops of water falling through a fine hole
    • c) The turning of gears driven by a hanging weight
    • d) Very rapid vibrations of a quartz crystal

  2. 2.A sundial, an hourglass and an atomic clock look nothing alike. What do they have in common?

    • a) Each of them can measure a thousandth of a second
    • b) Each of them counts a process that repeats at a steady rate
    • c) Each of them was invented in the same century
    • d) Each of them needs sunlight to work

  3. 3.Two pendulums hang side by side. They are the same length, but one has a much heavier bob. What can you say about their time periods?

    • a) They are the same, because the time period depends on length rather than on the mass of the bob
    • b) There is no way to say without timing them
    • c) The heavier bob gives the shorter time period, because it swings with more force
    • d) The heavier bob gives the longer time period, because it is harder to move

  4. 4.A journey takes 6 hours. How many minutes is that? Answer with a number.

  5. 5.Match each old timekeeping device to the steadily repeating thing it counted.

    • Sundial
    • Water clock
    • Hourglass
    • Candle clock
    • water flowing out of, or into, a vessel
    • a marked candle burning down
    • sand running from one bulb to the other
    • the moving shadow an object casts in sunlight

  6. 6.Put the stages of one oscillation of a pendulum in order, starting from the moment the bob leaves the mean position.

    • It swings across to the other extreme position and turns
    • It reaches one extreme position and turns
    • The bob leaves the mean position
    • It arrives back at the mean position

  7. 7.The time a pendulum takes to complete one oscillation has a two-word name. What is it?

  8. 8.What is the SI unit of time? Give the word, not the symbol.

Measuring time · Class 7 Science · www.arenapublications.com/learn

Class 7 Science · 8 of 12

Speed and motion

Work out speed, distance or time from the other two, choose between m/s and km/h, and tell uniform linear motion from non-uniform.

Before you start

A train leaves station A and reaches station D. Its position along the straight track is marked out below.

0120

Read the marks as the position of a train at equal intervals of time. When each gap between successive positions matches the one before, the speed is not changing and the motion is uniform. When the gaps grow or shrink, the speed is changing and the motion is non-uniform.

  1. 1.A train travels at a speed of 90 kilometres per hour. How many hours does it take to cover 360 kilometres? Answer with a number.

  2. 2.Two trains are timed over the same hour. Train X covers 20 kilometres in each ten-minute interval. Train Y covers 20, then 15, then 25. Which is in uniform linear motion, and how do you know?

    • a) Train Y, because its distances add up to the same total
    • b) Both, because both travel along a straight track
    • c) Train X, because it covers equal distances in equal intervals of time
    • d) Neither, because no real train holds one speed for long

  3. 3.What makes a motion uniform linear motion?

    • a) The object keeps to one speed, whatever path it takes
    • b) The object covers the same distance as another object in the same time
    • c) The object moves along a straight line, whatever its speed does
    • d) The object moves along a straight line at a constant speed

  4. 4.A runner covers 400 metres in 50 seconds. What is the runner's speed in metres per second? Answer with a number.

  5. 5.Three sprinters are part-way through a race on a straight track and one of them is ahead of the others. What does that tell you?

    • a) She has a longer stride, which is a different thing from speed
    • b) She has covered more distance in the same time, so she is the faster
    • c) She started before the others did
    • d) Nothing until the race is over

  6. 6.The chapter calls uniform linear motion an idealisation. Why?

    • a) Objects are seldom found holding a constant speed for long, which is why average speeds are used
    • b) It applies to trains but to nothing else
    • c) Straight tracks do not exist in practice
    • d) Speed cannot be measured accurately enough to check it

  7. 7.Sort each stretch of a train's journey along a straight track.

    Groups: Uniform linear motion · Non-uniform linear motion

    • A train covering the same distance in each ten-minute interval
    • A train pulling out of a station and picking up speed
    • A train covering different distances in successive ten-minute intervals
    • A train slowing down as it comes into a station
    • A train running at an unchanging speed along a straight stretch

  8. 8.A train covers 300 kilometres in 4 hours. What is its speed in kilometres per hour? Answer with a number.

Speed and motion · Class 7 Science · www.arenapublications.com/learn

Class 7 Science · 9 of 12

Life processes in animals

Follow food through the alimentary canal and say what each part does, tell breathing from respiration, and match an animal to the way it takes in oxygen.

Before you start

The parts of the human respiratory system, from the nostrils down.

12345
  1. 1. Nostrils
  2. 2. Windpipe
  3. 3. Lung
  4. 4. Rib cage
  5. 5. Diaphragm

Air comes in at the nostrils, down the windpipe, and into branches that end in tiny balloon-like sacs called alveoli inside the lungs. The rib cage guards the lungs; the dome-shaped diaphragm below them does the pulling.

  1. 1.Inhaled air is nearly 21 per cent oxygen; exhaled air is nearly 16 per cent oxygen. How many percentage points of oxygen were taken from the air? Answer with a number.

  2. 2.Why is the inner lining of the small intestine covered in thousands of finger-like projections?

    • a) They stop acid from the stomach reaching the intestine wall
    • b) They increase the surface area, so nutrients are absorbed efficiently
    • c) They grip the food and stop it moving on too fast
    • d) They make the digestive juices the small intestine needs

  3. 3.The large intestine is shorter than the small intestine. Why is it called large?

    • a) It does more of the digesting than any other part
    • b) It holds more food at one time than the stomach
    • c) It is wider than the small intestine
    • d) It was discovered before the small intestine was

  4. 4.What does the acid in the stomach do, besides helping to break down proteins?

    • a) It turns starch into sugar
    • b) It kills many harmful bacteria
    • c) It absorbs nutrients into the blood
    • d) It stores the food until the intestine is ready

  5. 5.Put the parts of the alimentary canal in the order food passes through them, starting at the mouth.

    • Large intestine
    • Rectum
    • Oesophagus
    • Stomach
    • Small intestine
    • Mouth
    • Anus

  6. 6.The finest branches inside the lungs end in tiny balloon-like sacs, and it is across their thin walls that gases are exchanged. What are those sacs called?

  7. 7.A cow brings partially digested grass back up to its mouth and chews it thoroughly. What is that process called?

  8. 8.What is the difference between breathing and respiration?

    • a) They are two words for the same process
    • b) Breathing happens in the lungs; respiration happens in the nose
    • c) Breathing is what animals do; respiration is what plants do
    • d) Breathing is a physical process moving air in and out; respiration is a chemical process using oxygen to release energy from food

Life processes in animals · Class 7 Science · www.arenapublications.com/learn

Class 7 Science · 10 of 12

Life processes in plants

Say what photosynthesis needs and what it gives back, read the experiment that proves each ingredient, and name the tubes that carry water up and food out.

Before you start

The parts of a plant, and what each one does with water and with food.

123
  1. 1. Leaf
  2. 2. Stem
  3. 3. Roots

The leaf is where the food is made. Water and minerals go up from the roots through tubes called xylem, inside the stem. Food made in the leaves goes out through a second set of tubes called phloem, to wherever the plant needs it or stores it. Tiny pores in the leaf surface, the stomata, let gases in and out.

  1. 1.Three identical saplings are grown for two weeks: A in sunlight with water, B in sunlight without water, C in the dark with water. What do their fates show?

    • a) A plant needs sunlight and can manage without water
    • b) A plant needs both sunlight and water to grow
    • c) Neither sunlight nor water makes much difference over two weeks
    • d) A plant needs water and can manage without sunlight

  2. 2.Why does the chapter call leaves the food factories of a plant?

    • a) They are the part of the plant that animals eat most often
    • b) They take in the water and minerals the plant lives on
    • c) They are the primary site of photosynthesis, where the food is made
    • d) They store most of the plant's food until it is needed

  3. 3.The food a plant makes is first produced as a simple carbohydrate, which the plant later turns into starch for storage. What is that simple carbohydrate?

  4. 4.What is the name of the process by which a plant prepares its food in the presence of sunlight and chlorophyll?

  5. 5.Tiny pores on the surface of a leaf, seen under a microscope in a peel of its underside, let gases in and out. What are they called?

  6. 6.A potato slice turns blue-black with iodine, so it holds starch. Where was that starch made?

    • a) In the potato itself, which photosynthesises underground
    • b) In the leaves, and carried down to the potato through the phloem
    • c) In the stem, from water carried up by the xylem
    • d) In the roots, from minerals taken out of the soil

  7. 7.Which pair of ingredients does a plant draw from its surroundings to make food?

    • a) Carbon dioxide from the soil and oxygen from the air
    • b) Oxygen from the air and glucose from the soil
    • c) Carbon dioxide from the air and water from the soil
    • d) Starch from the soil and sunlight from the sky

  8. 8.Sort each substance by the part it plays in photosynthesis.

    Groups: Taken in by photosynthesis · Given out by photosynthesis

    • Water
    • Carbon dioxide
    • Oxygen
    • Glucose

Life processes in plants · Class 7 Science · www.arenapublications.com/learn

Class 7 Science · 11 of 12

Light, shadows and reflection

Tell luminous objects from non-luminous, use the straight-line rule to explain shadows, and give the four properties of an image in a plane mirror.

Before you start

A torch, an opaque object and a screen — the three parts of a shadow set-up.

1234
  1. 1. Torch
  2. 2. Object
  3. 3. Screen
  4. 4. Shadow

Take away any one of the three and there is nothing to see: no light, no object to block it, or no surface for the dark patch to land on. In everyday life a wall, a floor or the ground plays the part of the screen.

  1. 1.A red ball and a blue ball of the same shape are held in the same place in front of a torch. What can you say about their shadows?

    • a) The red ball casts the darker shadow, because red is the deeper colour
    • b) One shadow is reddish and the other bluish
    • c) Both shadows are the same, because changing an object's colour does not change its shadow's colour
    • d) The blue ball casts no shadow, because blue lets light through

  2. 2.Sort each material by how much light gets through it.

    Groups: Transparent · Translucent · Opaque

    • Tracing paper
    • Thick cloth
    • Glass
    • Cardboard

  3. 3.Sort each of these by whether it gives out light of its own.

    Groups: Luminous · Non-luminous

    • A mirror
    • Lightning
    • The Moon
    • The Pole Star
    • The Sun
    • A firefly

  4. 4.A candle flame shines through a pinhole in a card onto a screen behind it. What does the image look like?

    • a) Too faint to have a shape
    • b) Upside down
    • c) The right way up
    • d) Left and right swapped, but the right way up

  5. 5.What three things do you need in order to see a shadow?

    • a) A source of light, a transparent object, and a mirror
    • b) A source of light, an opaque object, and a screen
    • c) A mirror, an opaque object, and a screen
    • d) Sunlight, a coloured object, and a dark room

  6. 6.Which set of properties describes the image formed by a plane mirror?

    • a) Smaller than the object, erect, and obtainable on a screen
    • b) Larger than the object, upside down, and laterally inverted
    • c) Same size as the object, upside down, and obtainable on a screen
    • d) Same size as the object, erect, laterally inverted, and not obtainable on a screen

  7. 7.Why is the word AMBULANCE painted reversed across the front of an ambulance?

    • a) So that it stays readable when the ambulance is moving fast
    • b) So that it can be read from a great distance
    • c) So that it looks different from ordinary vehicle lettering
    • d) So that it reads the right way round in the rear-view mirror of the vehicle ahead

  8. 8.Why do we see the Moon at night, given that it is a non-luminous object?

    • a) It glows from the heat stored in its rocks
    • b) It is lit by the lights of the Earth below it
    • c) It gives out a faint light of its own, weaker than a star's
    • d) It reflects the light the Sun casts on it

Light, shadows and reflection · Class 7 Science · www.arenapublications.com/learn

Class 7 Science · 12 of 12

The Earth, the Moon and the Sun

Tell rotation from revolution, explain day, night and the seasons from the Earth's turning and its tilt, and say what lines up during each kind of eclipse.

Before you start

The Sun, the Moon and the Earth, lined up for a solar eclipse.

123
  1. 1. The Sun
  2. 2. The Moon
  3. 3. The Earth

The Moon sits between the Sun and the Earth and throws a small shadow onto the Earth's surface. Stand inside that shadow and the Sun is hidden — a total solar eclipse. Stand where the Moon covers part of the Sun and you see a partial one.

  1. 1.Match each kind of eclipse to what is happening.

    • Solar eclipse
    • Lunar eclipse
    • A Moon completely inside the Earth's shadow
    • a total lunar eclipse, with the Moon turned dark red
    • the Moon comes between the Sun and the Earth
    • the Earth comes between the Sun and the Moon

  2. 2.Why does the Northern Hemisphere have summer in June?

    • a) It is tilted towards the Sun, so the sunlight is more intense and lasts more than 12 hours a day
    • b) The Sun gives out more heat during those months
    • c) The Earth rotates more slowly in June, giving longer days
    • d) It is passing through the part of the orbit nearest the Sun

  3. 3.Seen from above the North Pole, which way does the Earth rotate?

    • a) Clockwise, which is from West to East
    • b) Anti-clockwise, which is from East to West
    • c) Clockwise, which is from East to West
    • d) Anti-clockwise, which is from West to East

  4. 4.Here are the Sun, the Earth and the Moon during a lunar eclipse. Tap the body whose shadow is falling on the Moon.

    Write the number of the part.

    123

  5. 5.The Earth turns about an imaginary line running through its geographic North Pole and South Pole. What is that line called?

  6. 6.How does watching a lunar eclipse differ from watching a solar one?

    • a) A lunar eclipse can be watched safely through binoculars but not directly
    • b) An eclipsed full Moon can be watched safely with the naked eye
    • c) A lunar eclipse also needs eye protection, of a different kind
    • d) A lunar eclipse lasts a few seconds, so there is no time to look

  7. 7.Sort each motion by which of the two kinds it is.

    Groups: Rotation · Revolution

    • The turning that brings day and night
    • The Earth travelling round the Sun
    • The Earth spinning on its own axis
    • The Moon travelling round the Earth

  8. 8.What causes the seasons on the Earth?

    • a) The hemisphere tilted towards the Sun being closer to it
    • b) The Earth being at different distances from the Sun over the year
    • c) The Earth rotating faster in some months than in others
    • d) The tilt of the Earth's axis, together with the Earth's spherical shape

The Earth, the Moon and the Sun · Class 7 Science · www.arenapublications.com/learn

Answer keys — Class 7 Science

In the same order as the worksheets.

Acidic, basic and neutral substances

  1. 1.
    • neutralisation
    • neutralization
    • a neutralisation reaction
    • neutralisation reaction
  2. 2. 2 — Basic
  3. 3. c) An olfactory indicator, whose smell changes
  4. 4. 1. Wash the fallen rose petals in water 2. Crush the petals with a mortar and pestle 3. Pour hot water over the crushed petals and cover the tumbler 4. Filter off the coloured liquid and keep it as the extract
  5. 5. Soil that is too acidic → treated with lime; Soil that is basic → treated with manure and composted leaves; Acidic factory waste → treated with a basic substance before release
  6. 6.
    • acid-base indicator
    • acid base indicator
    • indicator
  7. 7. Lemon juice → Acidic; Tamarind water → Acidic; Vinegar → Acidic; Soap solution → Basic; Lime water → Basic; Washing powder solution → Basic; Sugar solution → Neutral; Salt solution → Neutral
  8. 8. b) It is acidic, or it is neutral

Circuits and their components

  1. 1. d) It glows just as before, because the circuit is still complete
  2. 2.
    • battery
    • a battery
  3. 3. Electric cell → a portable source of electrical energy; Switch → completes or breaks the circuit; Filament → gets hot and glows to give light
  4. 4.
    • circuit diagram
    • a circuit diagram
    • the circuit diagram
  5. 5. b) Copper costs less and there is plenty of it, and it conducts nearly as well
  6. 6. 1. The positive terminal of the cell 2. The switch, closed to ON 3. The filament of the lamp 4. The negative terminal of the cell
  7. 7. b) The positive terminal
  8. 8. d) It is open — a gap is left that the current cannot cross

Metals and non-metals

  1. 1. conduction
  2. 2. rust
  3. 3. c) Brittle
  4. 4. Nitrogen → goes into making fertilisers; Chlorine → used to purify water; Iodine → put on a wound as an antiseptic
  5. 5. Malleability → can be beaten into thin sheets; Ductility → can be drawn into wires; Sonority → gives a ringing sound when struck
  6. 6. b) Because those two names are for elements, and these materials are not elements
  7. 7. corrosion
  8. 8. Copper → Metal; Aluminium → Metal; Iron → Metal; Magnesium → Metal; Sulfur → Non-metal; Carbon → Non-metal; Oxygen → Non-metal; Nitrogen → Non-metal

Physical and chemical changes

  1. 1. b) They cannot be reversed
  2. 2. a) Carbon dioxide
  3. 3. Combustion → a substance reacts with oxygen, giving out heat or light; Weathering → breaks rock down where it lies, and eventually makes soil; Erosion → carries broken rock away by wind or flowing water
  4. 4. c) The state of a substance may change, and no new substance is formed
  5. 5. Melting an ice cube → Can be reversed; Boiling water → Can be reversed; Chopping vegetables → Cannot be reversed; Making popcorn from corn → Cannot be reversed
  6. 6. b) Physical, and it can be reversed
  7. 7. Melting an ice cube → Physical change; Crushing chalk into powder → Physical change; Folding paper into a shape → Physical change; Rusting of an iron nail → Chemical change; Burning a magnesium ribbon → Chemical change; Adding baking soda to vinegar → Chemical change; Cooking food → Chemical change
  8. 8. b) It cuts off the supply of air, so the burning has no oxygen

Adolescence: growth and change

  1. 1. c) Many healthy girls have cycles anywhere from 21 to 35 days
  2. 2. puberty
  3. 3. Eating a balanced diet → Looks after health in adolescence; Taking regular exercise → Looks after health in adolescence; Keeping the body clean → Looks after health in adolescence; Chewing tobacco → Harms health in adolescence; Drinking alcohol → Harms health in adolescence
  4. 4. b) His voice box is growing
  5. 5. b) Once a person starts taking it, they develop a strong urge to take it again and again
  6. 6. Calcium → helps bones grow well; Proteins → help growth, strength and energy; Iron → helps blood to form
  7. 7.
    • hormones
    • hormone
  8. 8. 10

Heat transfer in nature

  1. 1. d) Heavy extraction for a growing population, and concrete surfaces that leave less room for water to soak in
  2. 2. Conduction → heat passes along, and the particles stay where they are; Convection → the heated particles themselves move, carrying the heat; Radiation → heat crosses with no medium to carry it
  3. 3. d) Gravel, because the spaces between its particles are the widest
  4. 4. 1. Water at the bottom is heated by the flame 2. The heated water expands and becomes lighter 3. That lighter water rises up through the middle 4. Cooler, heavier water sinks down the sides to take its place
  5. 5. d) Radiation
  6. 6.
    • aquifer
    • an aquifer
    • aquifers
  7. 7. Steel → Good conductor of heat; Aluminium → Good conductor of heat; Wood → Poor conductor of heat; Glass → Poor conductor of heat; Clay → Poor conductor of heat; Air → Poor conductor of heat
  8. 8. b) It reflects most of the heat falling on it, while dark surfaces absorb more

Measuring time

  1. 1. d) Very rapid vibrations of a quartz crystal
  2. 2. b) Each of them counts a process that repeats at a steady rate
  3. 3. a) They are the same, because the time period depends on length rather than on the mass of the bob
  4. 4. 360
  5. 5. Sundial → the moving shadow an object casts in sunlight; Water clock → water flowing out of, or into, a vessel; Hourglass → sand running from one bulb to the other; Candle clock → a marked candle burning down
  6. 6. 1. The bob leaves the mean position 2. It reaches one extreme position and turns 3. It swings across to the other extreme position and turns 4. It arrives back at the mean position
  7. 7.
    • time period
    • the time period
  8. 8. second

Speed and motion

  1. 1. 4
  2. 2. c) Train X, because it covers equal distances in equal intervals of time
  3. 3. d) The object moves along a straight line at a constant speed
  4. 4. 8
  5. 5. b) She has covered more distance in the same time, so she is the faster
  6. 6. a) Objects are seldom found holding a constant speed for long, which is why average speeds are used
  7. 7. A train covering the same distance in each ten-minute interval → Uniform linear motion; A train running at an unchanging speed along a straight stretch → Uniform linear motion; A train covering different distances in successive ten-minute intervals → Non-uniform linear motion; A train pulling out of a station and picking up speed → Non-uniform linear motion; A train slowing down as it comes into a station → Non-uniform linear motion
  8. 8. 75

Life processes in animals

  1. 1. 5
  2. 2. b) They increase the surface area, so nutrients are absorbed efficiently
  3. 3. c) It is wider than the small intestine
  4. 4. b) It kills many harmful bacteria
  5. 5. 1. Mouth 2. Oesophagus 3. Stomach 4. Small intestine 5. Large intestine 6. Rectum 7. Anus
  6. 6.
    • alveoli
    • alveolus
  7. 7. rumination
  8. 8. d) Breathing is a physical process moving air in and out; respiration is a chemical process using oxygen to release energy from food

Life processes in plants

  1. 1. b) A plant needs both sunlight and water to grow
  2. 2. c) They are the primary site of photosynthesis, where the food is made
  3. 3. glucose
  4. 4. photosynthesis
  5. 5.
    • stomata
    • stoma
  6. 6. b) In the leaves, and carried down to the potato through the phloem
  7. 7. c) Carbon dioxide from the air and water from the soil
  8. 8. Carbon dioxide → Taken in by photosynthesis; Water → Taken in by photosynthesis; Glucose → Given out by photosynthesis; Oxygen → Given out by photosynthesis

Light, shadows and reflection

  1. 1. c) Both shadows are the same, because changing an object's colour does not change its shadow's colour
  2. 2. Glass → Transparent; Tracing paper → Translucent; Cardboard → Opaque; Thick cloth → Opaque
  3. 3. The Sun → Luminous; The Pole Star → Luminous; Lightning → Luminous; A firefly → Luminous; The Moon → Non-luminous; A mirror → Non-luminous
  4. 4. b) Upside down
  5. 5. b) A source of light, an opaque object, and a screen
  6. 6. d) Same size as the object, erect, laterally inverted, and not obtainable on a screen
  7. 7. d) So that it reads the right way round in the rear-view mirror of the vehicle ahead
  8. 8. d) It reflects the light the Sun casts on it

The Earth, the Moon and the Sun

  1. 1. Solar eclipse → the Moon comes between the Sun and the Earth; Lunar eclipse → the Earth comes between the Sun and the Moon; A Moon completely inside the Earth's shadow → a total lunar eclipse, with the Moon turned dark red
  2. 2. a) It is tilted towards the Sun, so the sunlight is more intense and lasts more than 12 hours a day
  3. 3. d) Anti-clockwise, which is from West to East
  4. 4. 2 — The Earth
  5. 5.
    • axis
    • the axis
    • axis of rotation
    • the axis of rotation
  6. 6. b) An eclipsed full Moon can be watched safely with the naked eye
  7. 7. The Earth spinning on its own axis → Rotation; The turning that brings day and night → Rotation; The Earth travelling round the Sun → Revolution; The Moon travelling round the Earth → Revolution
  8. 8. d) The tilt of the Earth's axis, together with the Earth's spherical shape

Class 7 Science · www.arenapublications.com/learn