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Term pack

Year 7 Science

Name: ________________________

Skills in this pack

  • The Earth, the Moon and the Sun
  • Methods of separation
  • Metals and non-metals
  • Physical and chemical changes
  • Circuits and their components
  • Light, shadows and reflection
  • Heat transfer in nature
  • Measuring time

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Year 7 Science · 1 of 8

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.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

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

  3. 3.Why do the southern states of India feel the change of seasons less strongly than places further north?

    • a) Their days run shorter than 12 hours the year round
    • b) They are closer to the Sun, so they stay warm the year round
    • c) The Earth's tilt does not affect the Southern Hemisphere
    • d) They lie close to the equator, where daylight and sunlight intensity vary little through the year

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

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

  5. 5.About how many hours does the Earth take to complete one rotation?

    Mark the line with an X.

    0123456789101112131415161718192021222324252627282930

  6. 6.A solar eclipse is happening. How should it be watched?

    • a) At an eclipse-viewing event, using eye protection made for solar viewing
    • b) Directly with the naked eye, since the Moon is blocking most of the Sun
    • c) Through sunglasses, which cut the glare down enough
    • d) Through binoculars, so the eclipse can be seen in detail

  7. 7.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
    • the Earth comes between the Sun and the Moon
    • a total lunar eclipse, with the Moon turned dark red

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

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

Year 7 Science · 2 of 8

Methods of separation

Name the everyday methods for pulling a mixture apart, and pick the right one for a given mixture.

Before you start

The stages of clearing a pan of tea, and where the leaves end up at each one.

123
  1. 1. Sedimentation — the leaves settle at the bottom
  2. 2. Decantation — the tea is poured off the settled leaves
  3. 3. Filtration — the strainer catches the leaves still floating

Three stages, and each one leaves the tea a little cleaner. Decantation on its own still lets a few leaves through, which is why the strainer comes last.

  1. 1.Iron filings are mixed into a heap of sand. Which method gets the filings out?

    • a) Magnetic separation
    • b) Evaporation
    • c) Decantation
    • d) Winnowing

  2. 2.Sort each method by what it pulls apart.

    Groups: A solid from another solid · A solid from a liquid

    • Winnowing
    • Evaporation
    • Sieving
    • Magnetic separation
    • Sedimentation
    • Filtration
    • Handpicking

  3. 3.Sand has been stirred into water but has not dissolved. Which method separates it out?

    • a) Filtration
    • b) Threshing
    • c) Churning
    • d) Evaporation

  4. 4.Heavier insoluble bits are left to settle at the bottom of a liquid. What is that process called?

  5. 5.Put the three stages of clearing tea leaves out of a pan of tea back into order.

    • Leave the vessel undisturbed so the tea leaves settle at the bottom
    • Tilt the vessel and pour the tea off
    • Pour the tea through a strainer to catch the leaves still in it

  6. 6.Match each method of separation to what is done in it.

    • Winnowing
    • Sieving
    • Decantation
    • Magnetic separation
    • Threshing
    • using a magnet to draw the magnetic pieces out
    • beating stalks to free the grains
    • blowing air to carry the lighter husk away
    • tilting the vessel to pour the liquid off the settled solid
    • passing a mixture through a sieve to separate by particle size

  7. 7.In churning, where does the butter end up?

    • a) Dissolved into the buttermilk
    • b) Settled at the bottom, because it is heavier
    • c) Spread evenly through the whole mixture
    • d) Floating at the top, because it is lighter

  8. 8.Stalks are beaten so the grains come free of them. What is that process called?

Methods of separation · Year 7 Science · www.arenapublications.com/learn

Year 7 Science · 3 of 8

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.An electrician's screwdriver has a plastic handle and they wear rubber gloves. Why?

    • a) Plastic and rubber are good conductors, so they carry the current safely to earth
    • b) Plastic and rubber grip better than metal does
    • c) Plastic and rubber keep the metal from rusting in a damp house
    • d) Plastic and rubber are poor conductors, so the current cannot reach them through it

  2. 2.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
    • c) Basic
    • d) Acidic first and then basic

  3. 3.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?

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

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

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

    • a) The softest metals are the ones that conduct heat worst
    • b) Some metals, such as sodium, are soft enough to cut with a knife
    • 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

  7. 7.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 first and then acidic
    • c) Neutral
    • d) Basic

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

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

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

Year 7 Science · 4 of 8

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

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

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

    Groups: Physical change · Chemical change

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

  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

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

  4. 4.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

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

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

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

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

  8. 8.Which statement describes a physical change?

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

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

Year 7 Science · 5 of 8

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

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

  2. 2.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) Silver and gold are insulators
    • c) Copper costs less and there is plenty of it, and it conducts nearly as well
    • d) Copper is the one metal that conducts electricity

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

    Write the number of the part.

    123

  5. 5.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?

  6. 6.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?

  7. 7.An LED is joined to a battery and does not light. What is the first thing worth checking?

    • a) Whether the battery has too many cells in it
    • b) Whether its filament has broken
    • c) Whether its longer wire is on the battery's positive terminal
    • d) Whether it has been fitted the right way up in its holder

  8. 8.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

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

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

Year 7 Science · 6 of 8

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.Why does a kaleidoscope show so many different patterns?

    • a) The tracing paper at the end scatters the light into new colours
    • b) Its three mirrors reflect each other's reflections, and turning it rearranges the pieces
    • c) Its single mirror flips the pattern each time it is turned
    • d) The coloured pieces inside change colour as the tube warms

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

  4. 4.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) The blue ball casts no shadow, because blue lets light through
    • d) Both shadows are the same, because changing an object's colour does not change its shadow's colour

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

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

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

    Groups: Luminous · Non-luminous

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

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

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

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

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

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

Year 7 Science · 7 of 8

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

  2. 2.Match each breeze to what it is and when it blows.

    • Sea breeze
    • Land breeze
    • cooler air moving from the land to the sea, by night
    • cooler air moving from the sea to the land, by day

  3. 3.The seeping of surface water down through soil and rock has a one-word name in this chapter. What is it?

  4. 4.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) Sand, because it is the driest of the three
    • c) They finish together, because the same water was poured into each
    • d) Gravel, because the spaces between its particles are the widest

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

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

  6. 6.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

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

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

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

    • a) It conducts heat away from the body faster than dark cloth
    • 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 is made of thinner cloth than dark clothing is

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

Year 7 Science · 8 of 8

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

  2. 2.A song lasts 4 minutes. How many seconds is that? Answer with a number.

  3. 3.What did Galileo find when he timed a swinging lamp against his own pulse?

    • a) The time for a swing depended on how heavy the lamp was
    • b) The swings got faster as the lamp slowed down
    • c) Each swing took a little longer than the one before
    • d) Each swing took the same time as the one before

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

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

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

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

  7. 7.A second pendulum takes 25 seconds to complete 10 oscillations. What is its time period, in seconds? Answer with a number.

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

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

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

Answer keys — Year 7 Science

In the same order as the worksheets.

The Earth, the Moon and the Sun

  1. 1. d) The Earth is rotating on its axis, and we are watching from it
  2. 2. c) An eclipsed full Moon can be watched safely with the naked eye
  3. 3. d) They lie close to the equator, where daylight and sunlight intensity vary little through the year
  4. 4. c) Anti-clockwise, which is from West to East
  5. 5. 24
  6. 6. a) At an eclipse-viewing event, using eye protection made for solar viewing
  7. 7. 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
  8. 8.
    • axis
    • the axis
    • axis of rotation
    • the axis of rotation

Methods of separation

  1. 1. a) Magnetic separation
  2. 2. Handpicking → A solid from another solid; Winnowing → A solid from another solid; Sieving → A solid from another solid; Magnetic separation → A solid from another solid; Filtration → A solid from a liquid; Sedimentation → A solid from a liquid; Evaporation → A solid from a liquid
  3. 3. a) Filtration
  4. 4. sedimentation
  5. 5. 1. Leave the vessel undisturbed so the tea leaves settle at the bottom 2. Tilt the vessel and pour the tea off 3. Pour the tea through a strainer to catch the leaves still in it
  6. 6. Winnowing → blowing air to carry the lighter husk away; Sieving → passing a mixture through a sieve to separate by particle size; Decantation → tilting the vessel to pour the liquid off the settled solid; Magnetic separation → using a magnet to draw the magnetic pieces out; Threshing → beating stalks to free the grains
  7. 7. d) Floating at the top, because it is lighter
  8. 8. threshing

Metals and non-metals

  1. 1. d) Plastic and rubber are poor conductors, so the current cannot reach them through it
  2. 2. c) Basic
  3. 3. corrosion
  4. 4. Nitrogen → goes into making fertilisers; Chlorine → used to purify water; Iodine → put on a wound as an antiseptic
  5. 5. d) Because those two names are for elements, and these materials are not elements
  6. 6. b) Some metals, such as sodium, are soft enough to cut with a knife
  7. 7. a) Acidic
  8. 8. Malleability → can be beaten into thin sheets; Ductility → can be drawn into wires; Sonority → gives a ringing sound when struck

Physical and chemical changes

  1. 1. c) Carbon dioxide
  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. a) Physical, and it can be reversed
  5. 5. d) A chemical change — iron in the rock has turned into iron oxide
  6. 6. 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
  7. 7. 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 vapour 4. The wax vapour burns, and the flame is what you see
  8. 8. c) The state of a substance may change, and no new substance is formed

Circuits and their components

  1. 1. b) The positive terminal
  2. 2. c) Copper costs less and there is plenty of it, and it conducts nearly as well
  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. 3 — Switch
  5. 5.
    • circuit diagram
    • a circuit diagram
    • the circuit diagram
  6. 6.
    • battery
    • a battery
  7. 7. c) Whether its longer wire is on the battery's positive terminal
  8. 8. Copper wire → Conductor; Metal key → Conductor; Aluminium foil → Conductor; Plastic scale → Insulator; Rubber eraser → Insulator; Wooden stick → Insulator

Light, shadows and reflection

  1. 1. lateral inversion
  2. 2. b) Its three mirrors reflect each other's reflections, and turning it rearranges the pieces
  3. 3. b) So that it reads the right way round in the rear-view mirror of the vehicle ahead
  4. 4. d) Both shadows are the same, because changing an object's colour does not change its shadow's colour
  5. 5. b) A source of light, an opaque object, and a screen
  6. 6. The Sun → Luminous; The Pole Star → Luminous; Lightning → Luminous; A firefly → Luminous; The Moon → Non-luminous; A mirror → Non-luminous
  7. 7. c) It reflects the light the Sun casts on it
  8. 8. a) Upside down

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. Sea breeze → cooler air moving from the sea to the land, by day; Land breeze → cooler air moving from the land to the sea, by night
  3. 3. infiltration
  4. 4. d) Gravel, because the spaces between its particles are the widest
  5. 5. a) Heavy extraction for a growing population, and concrete surfaces that leave less room for water to soak in
  6. 6. 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
  7. 7. a) Air is trapped between them, and air is a 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. b) Very rapid vibrations of a quartz crystal
  2. 2. 240
  3. 3. d) Each swing took the same time as the one before
  4. 4.
    • time period
    • the time period
  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. d) They are the same, because the time period depends on length rather than on the mass of the bob
  7. 7. 2.5
  8. 8. 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

Year 7 Science · www.arenapublications.com/learn