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Term pack

Grade 7 Science

Name: ________________________

Skills in this pack

  • Speed and motion
  • Circuits and their components
  • Heat transfer in nature
  • Metals and non-metals
  • Physical and chemical changes
  • Light, shadows and reflection
  • Life processes in animals
  • Life processes in plants
  • The Earth, the Moon and the Sun

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Grade 7 Science · 1 of 9

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

  2. 2.A bus moves at a speed of 50 kilometers per hour for 2 hours. How far does it go, in kilometers? Answer with a number.

  3. 3.A galloping horse reaches about 18 meters per second. A train is moving at 72 kilometers per hour. Which is faster?

    • a) They are the same speed in different units
    • b) The horse, because 18 is bigger than the train's speed once converted
    • c) The train, because 72 kilometers per hour is 20 meters per second
    • d) There is no way to compare them, because the units differ

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

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

  6. 6.Two trains are timed over the same hour. Train X covers 20 kilometers 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

  7. 7.A cyclist covers 240 meters in 30 seconds. What is the cyclist's speed in meters per second? Answer with a number.

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

    Groups: Uniform linear motion · Non-uniform linear motion

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

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

Grade 7 Science · 2 of 9

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.Why are the plug tops, switch covers and wire coverings in a house made of rubber, plastic or ceramic?

    • a) They are cheaper to make than the metal parts underneath
    • b) They are conductors, so they carry the current away from a person
    • c) They stop the metal underneath from rusting
    • d) They are insulators, so they keep the current from reaching a person

  2. 2.Each of these was held across the two free ends of a tester's wires. Sort them by whether the lamp glowed.

    Groups: Conductor · Insulator

    • Aluminum foil
    • Metal key
    • Rubber eraser
    • Wooden stick
    • Copper wire
    • Plastic scale

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

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

  4. 4.This is the circuit diagram of a torch. Tap the symbol for the switch.

    Write the number of the part.

    123

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

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

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

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

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

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

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

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

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

Grade 7 Science · 3 of 9

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.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

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

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

  3. 3.Rain, snow and hail are three forms of the same stage of the water cycle. What is the word that covers them together?

  4. 4.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?

  5. 5.Why is light-colored clothing more comfortable in summer?

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

  6. 6.Two thin blankets keep you warmer than one thick one. What does the chapter give as the reason?

    • a) Two blankets weigh more, and weight holds heat in
    • b) The outer blanket reflects heat back through the inner one
    • c) Thin cloth is woven more tightly than thick cloth
    • d) Air is trapped between them, and air is a poor conductor of heat

  7. 7.In conduction, what happens to the particles of the material the heat is crossing?

    • a) They travel from the hot end to the cold end, carrying the heat
    • b) They break apart and re-form further along
    • c) They stop moving, which is what makes the material feel hot
    • d) They stay where they are and pass the heat to their neighbors

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

    Groups: Good conductor of heat · Poor conductor of heat

    • Wood
    • Glass
    • Air
    • Aluminum
    • Steel
    • Clay

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

Grade 7 Science · 4 of 9

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.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 they are made in factories rather than dug out of the ground
    • c) Because those two names are for elements, and these materials are not elements
    • d) Because they are neither hard nor soft enough to be tested

  2. 2.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?

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

  4. 4.A gas made by burning a non-metal is dissolved in water. What nature would you expect that solution to have?

    • a) Acidic
    • b) Basic
    • c) Neutral
    • d) Basic first and then acidic

  5. 5.A spoonful of powder left after burning a metal is stirred into water. What nature would you expect that solution to have?

    • a) Neutral
    • b) Acidic first and then basic
    • c) Acidic
    • d) Basic

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

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

  7. 7.Which of these does the chapter say about how hard metals are?

    • a) Some metals, such as sodium, are soft enough to cut with a knife
    • b) The softest metals are the ones that conduct heat worst
    • c) A metal is hard by definition, so a soft material is not a metal
    • d) Metals grow harder the longer they are left in the open air

  8. 8.What has to reach an iron nail before a brown deposit forms on it?

    • a) Dry air on its own
    • b) Water and air together
    • c) Sunlight and dry air
    • d) Water on its own

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

Grade 7 Science · 5 of 9

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 vapor are physical changes — it is still wax. Inside the flame, that vapor 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 cannot be reversed
    • b) They can be reversed, but just in a laboratory
    • c) They can be reversed by grinding the rock back to sand
    • d) They reverse themselves each rainy season

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

    Groups: Physical change · Chemical change

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

  3. 3.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

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

  4. 4.A candle burns. Which kinds of change are going on?

    • a) Chemical alone, because a flame is a chemical reaction
    • b) Physical alone, because the wax is still wax the whole way through
    • c) Neither, because the candle is just getting shorter
    • d) Both — the wax melting and evaporating are physical, and the vapor burning is chemical

  5. 5.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 reflects the heat back onto the fire and smothers it with light
    • c) It cools the clothes below their ignition temperature at once
    • d) It cuts off the supply of air, so the burning has no oxygen

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

  7. 7.A black basalt rock exposed to damp air for a long time grows a red layer on its surface. What kind of change is that?

    • a) Neither — the rock was red underneath a black coating from the start
    • b) A physical change — the red is dust that has settled and stuck
    • c) A chemical change — iron in the rock has turned into iron oxide
    • d) A physical change — the surface has been worn smooth by rain

  8. 8.Follow the wax of a burning candle, starting from the step where the flame's heat melts the wax at the top of the candle.

    • The heat turns that wax into vapor
    • The liquid wax is drawn up the wick
    • The flame's heat melts the wax at the top of the candle
    • The wax vapor burns, and the flame is what you see

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

Grade 7 Science · 6 of 9

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.Raise your left hand at a plane mirror and the image seems to raise its right. This perceived left-right swap has a two-word name. What is it?

  2. 2.A shiny plate held in sunlight throws a bright patch onto a shaded wall, because it has changed the direction the light was traveling in. What is that change of direction called?

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

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

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

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

  5. 5.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, erect, laterally inverted, and not obtainable on a screen
    • d) Same size as the object, upside down, and obtainable on a screen

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

    Groups: Transparent · Translucent · Opaque

    • Cardboard
    • Tracing paper
    • Thick cloth
    • Glass

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

    Groups: Luminous · Non-luminous

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

  8. 8.Match each item to what it does.

    • A pinhole camera
    • An opaque object
    • A transparent object
    • A shadow
    • the dark region formed behind an object
    • blocks light completely
    • lets light pass almost completely through
    • forms an inverted image

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

Grade 7 Science · 7 of 9

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.What is the difference between breathing and respiration?

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

  2. 2.Match each digestive secretion to what it does.

    • Saliva
    • Bile from the liver
    • Pancreatic juice
    • Mucus
    • protects the stomach lining from the acid
    • breaks starch down into sugar
    • breaks fats into tiny droplets and neutralises acid
    • breaks down carbohydrates, proteins and fats

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

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

  4. 4.Respiration uses oxygen to break down glucose. What comes out of it?

    • a) Glucose and energy, with nothing given off
    • b) Carbon dioxide, water and energy
    • c) Oxygen, water and starch
    • d) Carbon dioxide and starch

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

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

  6. 6.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.

  7. 7.Sort each animal by the part of its body that takes in oxygen.

    Groups: Breathes with lungs · Breathes with gills · Breathes through moist skin

    • Earthworm
    • Fish
    • Tadpole
    • Snake
    • Lion

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

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

Grade 7 Science · 8 of 9

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

    Groups: Taken in by photosynthesis · Given out by photosynthesis

    • Oxygen
    • Carbon dioxide
    • Water
    • Glucose

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

  4. 4.Why is a leaf boiled in alcohol until it loses its color before the iodine test?

    • a) So that the chlorophyll starts making starch again
    • b) So that any color change from the iodine is easy to see
    • c) So that the iodine can soak through the waxy surface
    • d) So that the starch dissolves out of it into the alcohol

  5. 5.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?

  6. 6.A leaf with green and non-green patches is taken from a plant that has been standing in sunlight. Iodine is applied. What happens?

    • a) The green patches go blue-black and the non-green ones do not
    • b) Nothing changes color, because the leaf is still alive
    • c) The whole leaf goes blue-black, green patches and pale ones alike
    • d) The non-green patches go blue-black and the green ones do not

  7. 7.Put the steps of the starch test on a leaf in order, starting from softening the leaf in boiling water.

    • Decolourise it in alcohol standing in a beaker of boiling water
    • Put a few drops of dilute iodine solution on it
    • Soften the leaf in boiling water
    • A blue-black color means starch is present
    • Lay the pale leaf out on a plate

  8. 8.What does a plant do in respiration?

    • a) Break down glucose using oxygen, releasing carbon dioxide, water and energy
    • b) Break down oxygen using glucose, releasing sunlight
    • c) Store energy from sunlight without using any gas
    • d) Take in carbon dioxide and give out glucose

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

Grade 7 Science · 9 of 9

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
    • the Moon comes between the Sun and the Earth
    • a total lunar eclipse, with the Moon turned dark red
    • the Earth comes between the Sun and the Moon

  2. 2.The day-night cycle goes round and round with no true beginning, so start from the step where your place turns into the sunlight, and the Sun rises, and put the rest in order.

    • Your place is on the half turned away from the Sun — night
    • Your place turns out of the sunlight, and the Sun sets
    • Your place is on the half facing the Sun — daytime
    • Your place turns into the sunlight, and the Sun rises

  3. 3.About how many days does the Earth take to complete one revolution around the Sun? Answer with a number.

  4. 4.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) A lunar eclipse lasts a few seconds, so there is no time to look
    • c) An eclipsed full Moon can be watched safely with the naked eye
    • d) A lunar eclipse also needs eye protection, of a different kind

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

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

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

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

  7. 7.The Sun appears to travel across the sky from East to West each day. What is really going on?

    • a) The Sun stays still and the sky itself turns around it
    • b) The Sun is circling the Earth once a day
    • c) The Earth is revolving round the Sun, which takes a day
    • d) The Earth is rotating on its axis, and we are watching from it

  8. 8.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

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

Answer keys — Grade 7 Science

In the same order as the worksheets.

Speed and motion

  1. 1. 8
  2. 2. 100
  3. 3. c) The train, because 72 kilometers per hour is 20 meters per second
  4. 4. 75
  5. 5. 4
  6. 6. c) Train X, because it covers equal distances in equal intervals of time
  7. 7. 8
  8. 8. 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

Circuits and their components

  1. 1. d) They are insulators, so they keep the current from reaching a person
  2. 2. Copper wire → Conductor; Metal key → Conductor; Aluminum foil → Conductor; Plastic scale → Insulator; Rubber eraser → Insulator; Wooden stick → Insulator
  3. 3. 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
  4. 4. 3 — Switch
  5. 5. Electric cell → a portable source of electrical energy; Switch → completes or breaks the circuit; Filament → gets hot and glows to give light
  6. 6. d) It is open — a gap is left that the current cannot cross
  7. 7. d) It glows just as before, because the circuit is still complete
  8. 8. b) Copper costs less and there is plenty of it, and it conducts nearly as well

Heat transfer in nature

  1. 1. 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
  2. 2. b) Heavy extraction for a growing population, and concrete surfaces that leave less room for water to soak in
  3. 3. precipitation
  4. 4.
    • aquifer
    • an aquifer
    • aquifers
  5. 5. a) It reflects most of the heat falling on it, while dark surfaces absorb more
  6. 6. d) Air is trapped between them, and air is a poor conductor of heat
  7. 7. d) They stay where they are and pass the heat to their neighbors
  8. 8. Steel → Good conductor of heat; Aluminum → Good conductor of heat; Wood → Poor conductor of heat; Glass → Poor conductor of heat; Clay → Poor conductor of heat; Air → Poor conductor of heat

Metals and non-metals

  1. 1. c) Because those two names are for elements, and these materials are not elements
  2. 2. corrosion
  3. 3. rust
  4. 4. a) Acidic
  5. 5. d) Basic
  6. 6. d) Brittle
  7. 7. a) Some metals, such as sodium, are soft enough to cut with a knife
  8. 8. b) Water and air together

Physical and chemical changes

  1. 1. a) They cannot be reversed
  2. 2. 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
  3. 3. Melting an ice cube → Can be reversed; Boiling water → Can be reversed; Chopping vegetables → Cannot be reversed; Making popcorn from corn → Cannot be reversed
  4. 4. d) Both — the wax melting and evaporating are physical, and the vapor burning is chemical
  5. 5. d) It cuts off the supply of air, so the burning has no oxygen
  6. 6. a) Physical, and it can be reversed
  7. 7. c) A chemical change — iron in the rock has turned into iron oxide
  8. 8. 1. The flame's heat melts the wax at the top of the candle 2. The liquid wax is drawn up the wick 3. The heat turns that wax into vapor 4. The wax vapor burns, and the flame is what you see

Light, shadows and reflection

  1. 1. lateral inversion
  2. 2.
    • reflection
    • reflection of light
  3. 3. c) So that it reads the right way round in the rear-view mirror of the vehicle ahead
  4. 4. c) A source of light, an opaque object, and a screen
  5. 5. c) Same size as the object, erect, laterally inverted, and not obtainable on a screen
  6. 6. Glass → Transparent; Tracing paper → Translucent; Cardboard → Opaque; Thick cloth → Opaque
  7. 7. The Sun → Luminous; The Pole Star → Luminous; Lightning → Luminous; A firefly → Luminous; The Moon → Non-luminous; A mirror → Non-luminous
  8. 8. A pinhole camera → forms an inverted image; An opaque object → blocks light completely; A transparent object → lets light pass almost completely through; A shadow → the dark region formed behind an object

Life processes in animals

  1. 1. c) Breathing is a physical process moving air in and out; respiration is a chemical process using oxygen to release energy from food
  2. 2. Saliva → breaks starch down into sugar; Bile from the liver → breaks fats into tiny droplets and neutralises acid; Pancreatic juice → breaks down carbohydrates, proteins and fats; Mucus → protects the stomach lining from the acid
  3. 3. 1. Mouth 2. Oesophagus 3. Stomach 4. Small intestine 5. Large intestine 6. Rectum 7. Anus
  4. 4. b) Carbon dioxide, water and energy
  5. 5. d) It kills many harmful bacteria
  6. 6. 5
  7. 7. Lion → Breathes with lungs; Snake → Breathes with lungs; Fish → Breathes with gills; Tadpole → Breathes with gills; Earthworm → Breathes through moist skin
  8. 8. rumination

Life processes in plants

  1. 1. Carbon dioxide → Taken in by photosynthesis; Water → Taken in by photosynthesis; Glucose → Given out by photosynthesis; Oxygen → Given out by photosynthesis
  2. 2. c) They are the primary site of photosynthesis, where the food is made
  3. 3. photosynthesis
  4. 4. b) So that any color change from the iodine is easy to see
  5. 5. glucose
  6. 6. a) The green patches go blue-black and the non-green ones do not
  7. 7. 1. Soften the leaf in boiling water 2. Decolourise it in alcohol standing in a beaker of boiling water 3. Lay the pale leaf out on a plate 4. Put a few drops of dilute iodine solution on it 5. A blue-black color means starch is present
  8. 8. a) Break down glucose using oxygen, releasing carbon dioxide, water and energy

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. 1. Your place turns into the sunlight, and the Sun rises 2. Your place is on the half facing the Sun — daytime 3. Your place turns out of the sunlight, and the Sun sets 4. Your place is on the half turned away from the Sun — night
  3. 3. 365
  4. 4. c) An eclipsed full Moon can be watched safely with the naked eye
  5. 5. c) It is tilted towards the Sun, so the sunlight is more intense and lasts more than 12 hours a day
  6. 6. b) The tilt of the Earth's axis, together with the Earth's spherical shape
  7. 7. d) The Earth is rotating on its axis, and we are watching from it
  8. 8. 2 — The Earth

Grade 7 Science · www.arenapublications.com/learn