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Term pack

Year 8 Science

Name: ________________________

Skills in this pack

  • The cell, the basic unit of life
  • Life processes in animals
  • Life processes in plants
  • Microorganisms around us
  • Ecosystems and food chains
  • The particulate nature of matter
  • Elements, compounds and mixtures
  • Solutes, solvents and solutions
  • Density, and how to measure it
  • Forces: contact and non-contact
  • Magnetic and heating effects of current
  • Mirrors and lenses

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Year 8 Science · 1 of 12

The cell, the basic unit of life

Name the parts of a cell and what each does, tell a plant cell from an animal cell, and put the levels of organisation in order.

Before you start

Six parts of a plant cell are marked out here. Take them one at a time, and each will name itself.

123456
  1. 1. Cell wall
  2. 2. Cell membrane
  3. 3. Cytoplasm
  4. 4. Vacuole
  5. 5. Chloroplast
  6. 6. Nucleus

The cell wall and the chloroplasts are the two parts you would not find if this were an animal cell.

  1. 1.Match each part of a cell to the job it does.

    • Cell membrane
    • Cytoplasm
    • Nucleus
    • Cell wall
    • regulates what the cell does and how it grows
    • the place where most life processes happen
    • an extra outer layer that stiffens the cell
    • separates one cell from the next and lets material in and out

  2. 2.Who made better lenses in the 1660s, was the first to see and describe bacteria and blood cells, and is called the Father of Microbiology?

    • a) Acharya Kanad
    • b) Robert Hooke
    • c) Ananda Mohan Chakrabarty
    • d) Antonie van Leeuwenhoek

  3. 3.A bacterial cell differs from a plant, animal or fungal cell in one striking way. Which?

    • a) It has no cytoplasm
    • b) It has two nuclei rather than one
    • c) It has no well-defined nucleus, carrying a nucleoid instead
    • d) It has no cell membrane

  4. 4.The life of a complex organism begins with a single cell. Which one?

    • a) A cheek cell
    • b) The egg
    • c) A nerve cell
    • d) A muscle cell

  5. 5.How does the vacuole in a plant cell differ from those in an animal cell?

    • a) The plant cell has one large vacuole; an animal cell's are usually absent or small
    • b) Vacuoles are found in animal cells and not in plant cells
    • c) The vacuole in a plant cell is filled with chlorophyll
    • d) The plant cell has many tiny vacuoles; an animal cell has one large one

  6. 6.Robert Hooke looked at a thin slice of cork and saw rows of small empty compartments. What did he call each one, and why does it matter?

    • a) A tissue — the first use of the word in science
    • b) A microbe — the first use of the word in science
    • c) A cell — the first use of the word in science
    • d) A nucleus — the first use of the word in science

  7. 7.Match each level of organisation to what it is built from.

    • Tissue
    • Organ
    • Organ system
    • a group of similar cells
    • several organs carrying out one major body function
    • different tissues working together

  8. 8.Three kinds of human cell, sorted by their shape under the microscope.

    Groups: Spindle-shaped · Long and branched · Thin and flat

    • Cheek cell
    • Muscle cell
    • Nerve cell

The cell, the basic unit of life · Year 8 Science · www.arenapublications.com/learn

Year 8 Science · 2 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.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?

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

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

  4. 4.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
    • Snake
    • Tadpole
    • Lion
    • Fish

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

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

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

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

  7. 7.A frog begins life as a tadpole in water and grows into an adult that spends time on land. How does its breathing change?

    • a) The tadpole uses gills; the adult uses lungs on land and its skin in water
    • b) The tadpole uses lungs; the adult uses gills
    • c) It uses its skin throughout, and the lungs do nothing
    • d) It uses gills throughout, in water and on land alike

  8. 8.Tap the part of this alimentary canal where most of the digested nutrients are absorbed into the blood.

    Write the number of the part.

    12345

Life processes in animals · Year 8 Science · www.arenapublications.com/learn

Year 8 Science · 3 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.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
    • A blue-black colour means starch is present
    • Soften the leaf in boiling water
    • Put a few drops of dilute iodine solution on it
    • Lay the pale leaf out on a plate

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

  3. 3.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?

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

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

  5. 5.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 stem, from water carried up by the xylem
    • c) In the leaves, and carried down to the potato through the phloem
    • d) In the roots, from minerals taken out of the soil

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

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

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

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

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

Life processes in plants · Year 8 Science · www.arenapublications.com/learn

Year 8 Science · 4 of 12

Microorganisms around us

Name the main groups of microorganisms and say what they do for soil, food and crops.

  1. 1.Match each microorganism to the job it does for us.

    • Yeast
    • Lactobacillus
    • Rhizobium
    • traps nitrogen from the air for legume plants
    • turns milk into curd
    • makes bread and cake dough rise

  2. 2.Which bacterium ferments milk into curd, feeding on the milk sugar lactose? Give its name.

  3. 3.Manure forms best under certain conditions. Which does the chapter name?

    • a) Freezing temperatures and standing water
    • b) Complete darkness and dry conditions
    • c) An optimal temperature and an appropriate moisture level
    • d) Direct sunlight and dry soil

  4. 4.Microalgae live in water, soil, air and on trees, and make their own food using sunlight. What does the chapter say they release while doing so?

    • a) More than half of the Earth's carbon dioxide
    • b) The nitrogen that legumes take up
    • c) The methane in biogas
    • d) More than half of the Earth's oxygen supply

  5. 5.Why do pickles and murabbas keep for months without going mouldy?

    • a) The high concentration of salt or sugar stops microorganisms growing on them
    • b) They are sealed so tightly that no microorganism can reach them
    • c) Microorganisms cannot live on fruit once it has been cut
    • d) The spices in them kill any microorganism that lands

  6. 6.Sort these by whether the whole living thing is one cell or many.

    Groups: Unicellular · Multicellular

    • Yeast
    • Amoeba
    • Mould
    • Bacteria

  7. 7.Some microorganisms live in hot water springs and snow-cold zones. What does that tell you about them as a group?

    • a) They can live in extreme conditions as well as moderate ones
    • b) They can live at high temperatures but not at low ones
    • c) They live in extreme conditions and cannot survive moderate ones
    • d) They cannot survive anywhere that a plant cannot grow

  8. 8.Why do farmers grow legumes such as beans and peas in rotation with other crops?

    • a) Legumes use less water, so more is left in the soil for the next crop
    • b) Legumes drive away the pests that would attack the next crop
    • c) Legume roots break up hard soil so the next crop can spread its roots
    • d) Rhizobium in their root nodules adds nitrogen to the soil, leaving it healthier for the next crop

Microorganisms around us · Year 8 Science · www.arenapublications.com/learn

Year 8 Science · 5 of 12

Ecosystems and food chains

Separate the living and non-living parts of a habitat, build a food chain, and name the three ways two organisms can live together.

  1. 1.Sort these animals by what they eat.

    Groups: Herbivore · Carnivore · Omnivore

    • Crow
    • Fox
    • Deer
    • Mouse
    • Hare
    • Leopard

  2. 2.In the food chain grass → grasshopper → frog → snake, which one is the producer?

    • a) Grasshopper
    • b) Frog
    • c) Snake
    • d) Grass

  3. 3.Sort these ecosystems by whether they sit in water or on land.

    Groups: Aquatic ecosystem · Terrestrial ecosystem

    • Grassland
    • A pond
    • A forest
    • A river

  4. 4.Why does the chapter call competition for food, water and space a good thing for an ecosystem?

    • a) It stops organisms from eating one another
    • b) It removes the weakest organisms from the habitat
    • c) It increases the number of abiotic components
    • d) It helps control population size and keeps the ecosystem balanced

  5. 5.Put this grassland food chain in order, from what is eaten first to what eats last.

    • Eagle
    • Grass
    • Grasshopper
    • Frog
    • Snake

  6. 6.Put these four levels of nature in order, from the smallest upwards.

    • Ecosystem
    • Individual
    • Population
    • Community

  7. 7.In the chain grass → grasshopper → frog → snake, the frogs disappear. What happens to the grasshoppers and the snakes?

    • a) Grasshoppers increase, because nothing is eating them; snakes decrease, because their food has gone
    • b) Both increase, because one fewer animal is competing for space
    • c) Both stay the same, because the grass is unaffected
    • d) Grasshoppers decrease and snakes increase

  8. 8.What is the difference between a population and a community?

    • a) A community is smaller than a population
    • b) A population is the plants and a community is the animals
    • c) A population lives in water and a community on land
    • d) A population is organisms of one kind in a habitat; a community is the different populations sharing it

Ecosystems and food chains · Year 8 Science · www.arenapublications.com/learn

Year 8 Science · 6 of 12

The particulate nature of matter

Explain the three states of matter by how tightly their particles are held and how much space sits between them.

  1. 1.The particles of a solid are closely packed, but a little space is still left between them. What does the chapter say is in that space?

    • a) Air
    • b) Smaller particles of the same substance
    • c) Water vapour
    • d) Nothing

  2. 2.A grain of potassium permanganate is dropped into hot water, water at room temperature and ice-cold water. Where does the colour spread fastest, and why?

    • a) In the ice-cold water, because cold water holds more colour
    • b) At the same rate in each of the three, because the grain is the same size
    • c) In the hot water, because heating makes the particles move faster
    • d) In the room-temperature water, because the particles are most settled there

  3. 3.What are the spaces between the particles of a substance called? Give the two words.

  4. 4.Liquids and gases share two properties that solids do not: they flow, and they do not hold a fixed shape. What are the two of them called together?

    • a) Mixtures
    • b) Vapours
    • c) Fluids
    • d) Solutions

  5. 5.Sort the three states of matter by how strongly their particles pull on one another.

    Groups: Strongest attraction · Slightly weaker than in a solid · Negligible attraction

    • Liquid
    • Solid
    • Gas

  6. 6.What is the difference between boiling and evaporation, as the chapter puts it?

    • a) Boiling happens at the surface; evaporation happens throughout the liquid
    • b) Boiling is slow and evaporation is fast
    • c) Boiling turns a liquid into a solid; evaporation turns it into a gas
    • d) Boiling happens at one temperature and throughout the liquid; evaporation happens at any temperature and at the surface

  7. 7.Match each state of matter to what it does about shape and volume.

    • A solid
    • A liquid
    • A gas
    • keeps a definite volume but takes the shape of its container
    • keeps neither shape nor volume, and spreads through the space available
    • keeps a definite shape and a definite volume

  8. 8.A solid is heated until it melts. Put the four stages back into order.

    • The vibrations grow strong enough that particles leave their positions
    • The particles vibrate more vigorously
    • The solid turns into a liquid
    • The interparticle forces of attraction weaken

The particulate nature of matter · Year 8 Science · www.arenapublications.com/learn

Year 8 Science · 7 of 12

Elements, compounds and mixtures

Tell an element from a compound from a mixture, and say which of them can be taken apart by physical means.

  1. 1.Could you separate the hydrogen and oxygen in water by a physical method such as filtering, evaporating or using a magnet?

    • a) Yes — a strong enough magnet pulls the hydrogen out
    • b) No — the elements in a compound are held too tightly for any physical method
    • c) Yes — evaporating the water leaves the oxygen behind
    • d) No — because water contains just one element to begin with

  2. 2.Elements divide into two families. Sort these into theirs.

    Groups: Metal · Non-metal

    • Iron
    • Aluminium
    • Oxygen
    • Carbon
    • Sulfur
    • Gold

  3. 3.Silicon and boron sit awkwardly between the two families of elements. What are such elements called?

    • a) Compounds
    • b) Alloys
    • c) Metalloids
    • d) Minerals

  4. 4.In water, what is the ratio of the number of hydrogen atoms to the number of oxygen atoms? Write it as a ratio.

  5. 5.A packet of ghee is labelled 'pure'. A scientist looks at it and calls it impure. Why the disagreement?

    • a) In science, pure means safe to eat, and the ghee is not
    • b) The scientist thinks the ghee has had something cheaper added to it
    • c) In science, pure means made of a single substance, while in everyday use it means unadulterated
    • d) In science, any substance sold in a packet counts as impure

  6. 6.Sort these substances into the three kinds the chapter names.

    Groups: Element · Compound · Mixture

    • Sulfur
    • Water
    • Brass
    • Air
    • Gold
    • Sodium chloride

  7. 7.Sugar heated in a boiling tube turns brown, then black, and droplets of water appear near the open end. What does that show about sugar?

    • a) It is an element, since carbon is left behind
    • b) It is a mixture of carbon and water stirred together
    • c) It is a metal, since it darkens on heating
    • d) It is a compound, made of carbon, hydrogen and oxygen

  8. 8.A pure substance is one of two things. Which pair is it?

    • a) A compound or a mixture
    • b) A metal or a non-metal
    • c) An element or a mixture
    • d) An element or a compound

Elements, compounds and mixtures · Year 8 Science · www.arenapublications.com/learn

Year 8 Science · 8 of 12

Solutes, solvents and solutions

Name the solute and the solvent in a solution, tell a saturated solution from an unsaturated one, and say how temperature changes what will dissolve.

  1. 1.Each sip of a homemade oral rehydration solution tastes the same as the last. Why?

    • a) The sugar and salt cancel out each other's taste
    • b) The water dilutes both of them until neither can be tasted
    • c) The sugar settles at the bottom and the salt stays at the top
    • d) The sugar and salt are evenly distributed through the whole of the water

  2. 2.Spoons of salt are stirred into a glass of water one after another. Put the four stages back into order.

    • More spoons go in and still dissolve
    • A spoon is added that does not fully dissolve
    • The first spoon of salt dissolves completely
    • The undissolved salt settles at the bottom

  3. 3.Alcohol and water are mixed, with rather more water than alcohol. Which is the solute?

    • a) Neither, because two liquids cannot form a solution
    • b) The water, because it is a liquid
    • c) The alcohol, because it is the one present in the smaller amount
    • d) Both, because liquids mixed together are both solutes

  4. 4.Gases behave the other way round from solids. What happens to the solubility of a gas in water as the water warms up?

    • a) It decreases
    • b) It stays the same
    • c) It increases up to 50 °C and decreases after that
    • d) It increases

  5. 5.Why does dissolved oxygen matter in a pond?

    • a) It is what sustains the plants, fish and other organisms living in the water
    • b) It keeps the water from freezing in winter
    • c) It stops other gases from dissolving in the water
    • d) It makes the water taste better

  6. 6.The greatest amount of solute a fixed quantity of solvent will dissolve at a particular temperature has a one-word name. What is it?

  7. 7.For most solids dissolving in a liquid, what does raising the temperature do to the solubility?

    • a) It leaves it unchanged
    • b) It increases it
    • c) It decreases it
    • d) It increases it for salts and decreases it for sugars

  8. 8.In a glass of salt water, what is the water called? Give the one word.

Solutes, solvents and solutions · Year 8 Science · www.arenapublications.com/learn

Year 8 Science · 9 of 12

Density, and how to measure it

Calculate density from mass and volume, find the volume of an irregular solid by displacement, and say what heating does to density.

  1. 1.Object A has a mass of 200 g and a volume of 40 cm³. What is its density, in grams per cubic centimetre? Answer with a number.

  2. 2.A stone sculpture has a mass of 225 g and a volume of 90 cm³. What is its density, in grams per cubic centimetre? Answer with a number.

  3. 3.A substance is heated. What generally happens to its density, and why?

    • a) It decreases, because heating destroys some of the particles
    • b) It decreases, because the particles spread out so the volume grows while the mass stays the same
    • c) It increases, because heating adds energy and so adds mass
    • d) It stays the same, because density does not depend on temperature

  4. 4.A closed box is 12 cm long, 5 cm wide and 4 cm high. What is its volume, in cubic centimetres? Answer with a number.

  5. 5.A measuring cylinder has bigger marks 20 mL apart, and there are 10 small divisions between the 20 mL and 40 mL marks. What is the smallest volume it can read, in millilitres? Answer with a number.

  6. 6.Water is at its densest at 4 °C. As it cools further and turns to ice at 0 °C, what happens?

    • a) The mass decreases, which is what makes ice float
    • b) The density stays exactly the same, since freezing is a physical change
    • c) The particles pack closer together, so ice is denser and would sink but for the surface tension
    • d) The particles arrange themselves so as to take up more space, so ice is less dense and floats

  7. 7.Water in a measuring cylinder stands at 40 mL. A metal key is lowered in and the level rises to 47 mL. What is the key's volume, in cubic centimetres? Answer with a number.

  8. 8.Object B has a mass of 240 g and a volume of 60 cm³. What is its density, in grams per cubic centimetre? Answer with a number.

Density, and how to measure it · Year 8 Science · www.arenapublications.com/learn

Year 8 Science · 10 of 12

Forces: contact and non-contact

Sort forces by whether they need the objects to touch, read a spring balance, and keep weight and mass apart.

  1. 1.What is the SI unit of force called? Give the one word.

  2. 2.A spring balance measures up to 10 N, with a bigger mark at each newton. Which mark is at 6 N?

    Mark the line with an X.

    012345678910

  3. 3.Sort these forces by whether the two objects have to be touching for the force to act.

    Groups: Contact force · Non-contact force

    • Electrostatic force
    • Friction
    • Gravitational force
    • Magnetic force
    • Muscular force

  4. 4.A 1 kg object weighs 10 N on the Earth, 25.4 N on Jupiter, 9 N on Venus and 3.8 N on Mars. What does the same object weigh on the Moon?

    • a) 9 N
    • b) 10 N
    • c) 1.6 N
    • d) 3.8 N

  5. 5.A ball is thrown straight up. Starting from The object moves straight up, put what happens next back into order.

    • Its speed goes on decreasing
    • The object moves straight up
    • It stops momentarily at the top
    • It falls back down, its speed increasing

  6. 6.A closed empty bottle is pushed down into a bucket of water and released. It shoots back to the surface. What has pushed it?

    • a) Upthrust, the upward force a liquid applies on an object placed in it
    • b) Friction between the bottle and the water
    • c) Muscular force still stored in the bottle from the push
    • d) The gravitational force of the Earth, acting upwards in water

  7. 7.An object placed in a liquid floats rather than sinks. What does the chapter say about the two forces on it?

    • a) The buoyant force acts downwards and the gravitational force upwards
    • b) The gravitational force is greater than the buoyant force
    • c) The buoyant force and the gravitational force are equal
    • d) There is no gravitational force acting on a floating object

  8. 8.Two balloons are rubbed with the same woollen cloth and hung near each other. What do they do, and why?

    • a) They move together, because they have picked up charges of opposite kinds
    • b) They move apart, because they have picked up charges of the same kind and like charges repel
    • c) They move together, because rubbing makes both of them sticky
    • d) They hang still, because rubbing wool on rubber charges neither of them

Forces: contact and non-contact · Year 8 Science · www.arenapublications.com/learn

Year 8 Science · 11 of 12

Magnetic and heating effects of current

Explain how a current makes a magnet and how it makes heat, and say what changes the strength of an electromagnet.

  1. 1.Sort these two kinds of cell by whether they can be used again after they run down.

    Groups: Single use · Recharged and reused many times

    • Rechargeable battery
    • Dry cell

  2. 2.Why should a used battery go to an e-waste facility rather than into the household bin?

    • a) Household bins are too small for batteries
    • b) A used battery is completely inert and so has no value
    • c) It will start working again once it has been sorted
    • d) It can still contain acids and metals that may cause fires or harm the environment

  3. 3.The chapter lists what the heat generated in a wire depends on. Which list is right?

    • a) The material, thickness and length of the wire, and how long the current flows
    • b) The material of the wire and nothing else
    • c) The temperature of the room the circuit is in
    • d) The colour of the wire and the shape of the switch

  4. 4.Match each change you could make to an electromagnet with what it does.

    • Adding a second cell to the circuit
    • Winding more turns onto the coil
    • Reversing the direction of the current
    • Pulling the iron nail out of the coil
    • a weaker magnet, since the core is gone
    • a larger current, so a stronger magnet
    • the North and South ends swap over
    • a stronger magnet without changing the current

  5. 5.The north pole of a magnetic compass is attracted towards end A of an electromagnet. Which pole is end A?

    • a) Neither — an electromagnet has no poles
    • b) Both at once
    • c) North
    • d) South

  6. 6.A compass needle beneath a wire deflects when the switch is closed and returns when it is opened. What does the return show?

    • a) The current keeps flowing for a while after the switch is opened
    • b) The magnetic field disappears when the current stops flowing
    • c) The wire has become a permanent magnet
    • d) The compass needle has been demagnetised by the current

  7. 7.In the lemon cell built in the chapter, what plays the part of the electrolyte?

    • a) The lemon juice
    • b) The copper wire
    • c) The iron nail
    • d) The LED

  8. 8.Match each part of a Voltaic cell to what it is.

    • Electrodes
    • Electrolyte
    • A dead cell
    • one whose chemicals have been used up, so it supplies no more electricity
    • two metal rods of different materials
    • the liquid they are dipped in, usually a weak acid or salt solution

Magnetic and heating effects of current · Year 8 Science · www.arenapublications.com/learn

Year 8 Science · 12 of 12

Mirrors and lenses

Tell concave from convex for both mirrors and lenses, use the laws of reflection to find an angle, and say which of them gathers a beam and which spreads it.

  1. 1.Why is a convex mirror, rather than a plane one, fitted as a vehicle's side-view mirror?

    • a) It is cheaper to make than a plane mirror of the same size
    • b) It shows the traffic behind at a larger size
    • c) It shows the traffic behind the right way up, which a plane mirror cannot
    • d) It shows a much wider area of the road behind

  2. 2.You are handed a magnifying glass. Which kind of lens is it?

    • a) A convex lens
    • b) A spherical mirror
    • c) A plane lens
    • d) A concave lens

  3. 3.How does a concave lens differ from a convex one to look at?

    • a) It is thicker in the middle than at the edges
    • b) It is not transparent
    • c) It is thicker at the edges than in the middle
    • d) It is the same thickness throughout

  4. 4.A ray strikes a mirror, and the grey upright line is the normal at that point. Tap the angle of incidence.

    Write the number of the part.

    12

  5. 5.A ray of light strikes a mirror at an angle of 35° to the normal. What is the angle of reflection, in degrees? Answer with a number.

  6. 6.Parallel beams of light fall on each of these. Sort them by what happens to the beams afterwards.

    Groups: Converges the beam · Diverges the beam

    • Concave mirror
    • Concave lens
    • Convex lens
    • Convex mirror

  7. 7.Each of these is a mirror doing a job. Sort them by which kind of mirror is used.

    Groups: Concave mirror · Convex mirror

    • A dentist's mirror
    • The side-view mirror of a vehicle
    • A road safety mirror at a bend
    • The reflector of a torch
    • A store's surveillance mirror

  8. 8.The laws of reflection were worked out with a plane mirror. Which mirrors do they hold for?

    • a) Plane and concave mirrors, but not convex ones
    • b) Plane mirrors and nothing else
    • c) Curved mirrors, but not plane ones
    • d) Plane, concave and convex alike

Mirrors and lenses · Year 8 Science · www.arenapublications.com/learn

Answer keys — Year 8 Science

In the same order as the worksheets.

The cell, the basic unit of life

  1. 1. Cell membrane → separates one cell from the next and lets material in and out; Cytoplasm → the place where most life processes happen; Nucleus → regulates what the cell does and how it grows; Cell wall → an extra outer layer that stiffens the cell
  2. 2. d) Antonie van Leeuwenhoek
  3. 3. c) It has no well-defined nucleus, carrying a nucleoid instead
  4. 4. b) The egg
  5. 5. a) The plant cell has one large vacuole; an animal cell's are usually absent or small
  6. 6. c) A cell — the first use of the word in science
  7. 7. Tissue → a group of similar cells; Organ → different tissues working together; Organ system → several organs carrying out one major body function
  8. 8. Muscle cell → Spindle-shaped; Nerve cell → Long and branched; Cheek cell → Thin and flat

Life processes in animals

  1. 1. 5
  2. 2.
    • alveoli
    • alveolus
  3. 3. d) It kills many harmful bacteria
  4. 4. Lion → Breathes with lungs; Snake → Breathes with lungs; Fish → Breathes with gills; Tadpole → Breathes with gills; Earthworm → Breathes through moist skin
  5. 5. c) It is wider than the small intestine
  6. 6. d) Carbon dioxide, water and energy
  7. 7. a) The tadpole uses gills; the adult uses lungs on land and its skin in water
  8. 8. 4 — Small intestine

Life processes in plants

  1. 1. 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 colour means starch is present
  2. 2. photosynthesis
  3. 3.
    • stomata
    • stoma
  4. 4. a) They are the primary site of photosynthesis, where the food is made
  5. 5. c) In the leaves, and carried down to the potato through the phloem
  6. 6. d) Carbon dioxide from the air and water from the soil
  7. 7. c) So that any colour change from the iodine is easy to see
  8. 8. b) A plant needs both sunlight and water to grow

Microorganisms around us

  1. 1. Yeast → makes bread and cake dough rise; Lactobacillus → turns milk into curd; Rhizobium → traps nitrogen from the air for legume plants
  2. 2. lactobacillus
  3. 3. c) An optimal temperature and an appropriate moisture level
  4. 4. d) More than half of the Earth's oxygen supply
  5. 5. a) The high concentration of salt or sugar stops microorganisms growing on them
  6. 6. Bacteria → Unicellular; Amoeba → Unicellular; Yeast → Unicellular; Mould → Multicellular
  7. 7. a) They can live in extreme conditions as well as moderate ones
  8. 8. d) Rhizobium in their root nodules adds nitrogen to the soil, leaving it healthier for the next crop

Ecosystems and food chains

  1. 1. Deer → Herbivore; Hare → Herbivore; Leopard → Carnivore; Crow → Omnivore; Fox → Omnivore; Mouse → Omnivore
  2. 2. d) Grass
  3. 3. A pond → Aquatic ecosystem; A river → Aquatic ecosystem; A forest → Terrestrial ecosystem; Grassland → Terrestrial ecosystem
  4. 4. d) It helps control population size and keeps the ecosystem balanced
  5. 5. 1. Grass 2. Grasshopper 3. Frog 4. Snake 5. Eagle
  6. 6. 1. Individual 2. Population 3. Community 4. Ecosystem
  7. 7. a) Grasshoppers increase, because nothing is eating them; snakes decrease, because their food has gone
  8. 8. d) A population is organisms of one kind in a habitat; a community is the different populations sharing it

The particulate nature of matter

  1. 1. d) Nothing
  2. 2. c) In the hot water, because heating makes the particles move faster
  3. 3.
    • interparticle spaces
    • interparticle space
  4. 4. c) Fluids
  5. 5. Solid → Strongest attraction; Liquid → Slightly weaker than in a solid; Gas → Negligible attraction
  6. 6. d) Boiling happens at one temperature and throughout the liquid; evaporation happens at any temperature and at the surface
  7. 7. A solid → keeps a definite shape and a definite volume; A liquid → keeps a definite volume but takes the shape of its container; A gas → keeps neither shape nor volume, and spreads through the space available
  8. 8. 1. The particles vibrate more vigorously 2. The vibrations grow strong enough that particles leave their positions 3. The interparticle forces of attraction weaken 4. The solid turns into a liquid

Elements, compounds and mixtures

  1. 1. b) No — the elements in a compound are held too tightly for any physical method
  2. 2. Iron → Metal; Aluminium → Metal; Gold → Metal; Carbon → Non-metal; Sulfur → Non-metal; Oxygen → Non-metal
  3. 3. c) Metalloids
  4. 4. 2:1
  5. 5. c) In science, pure means made of a single substance, while in everyday use it means unadulterated
  6. 6. Gold → Element; Sulfur → Element; Water → Compound; Sodium chloride → Compound; Air → Mixture; Brass → Mixture
  7. 7. d) It is a compound, made of carbon, hydrogen and oxygen
  8. 8. d) An element or a compound

Solutes, solvents and solutions

  1. 1. d) The sugar and salt are evenly distributed through the whole of the water
  2. 2. 1. The first spoon of salt dissolves completely 2. More spoons go in and still dissolve 3. A spoon is added that does not fully dissolve 4. The undissolved salt settles at the bottom
  3. 3. c) The alcohol, because it is the one present in the smaller amount
  4. 4. a) It decreases
  5. 5. a) It is what sustains the plants, fish and other organisms living in the water
  6. 6. solubility
  7. 7. b) It increases it
  8. 8. solvent

Density, and how to measure it

  1. 1. 5
  2. 2. 2.5
  3. 3. b) It decreases, because the particles spread out so the volume grows while the mass stays the same
  4. 4. 240
  5. 5. 2
  6. 6. d) The particles arrange themselves so as to take up more space, so ice is less dense and floats
  7. 7. 7
  8. 8. 4

Forces: contact and non-contact

  1. 1. newton
  2. 2. 6
  3. 3. Muscular force → Contact force; Friction → Contact force; Magnetic force → Non-contact force; Electrostatic force → Non-contact force; Gravitational force → Non-contact force
  4. 4. c) 1.6 N
  5. 5. 1. The object moves straight up 2. Its speed goes on decreasing 3. It stops momentarily at the top 4. It falls back down, its speed increasing
  6. 6. a) Upthrust, the upward force a liquid applies on an object placed in it
  7. 7. c) The buoyant force and the gravitational force are equal
  8. 8. b) They move apart, because they have picked up charges of the same kind and like charges repel

Magnetic and heating effects of current

  1. 1. Dry cell → Single use; Rechargeable battery → Recharged and reused many times
  2. 2. d) It can still contain acids and metals that may cause fires or harm the environment
  3. 3. a) The material, thickness and length of the wire, and how long the current flows
  4. 4. Adding a second cell to the circuit → a larger current, so a stronger magnet; Winding more turns onto the coil → a stronger magnet without changing the current; Reversing the direction of the current → the North and South ends swap over; Pulling the iron nail out of the coil → a weaker magnet, since the core is gone
  5. 5. d) South
  6. 6. b) The magnetic field disappears when the current stops flowing
  7. 7. a) The lemon juice
  8. 8. Electrodes → two metal rods of different materials; Electrolyte → the liquid they are dipped in, usually a weak acid or salt solution; A dead cell → one whose chemicals have been used up, so it supplies no more electricity

Mirrors and lenses

  1. 1. d) It shows a much wider area of the road behind
  2. 2. a) A convex lens
  3. 3. c) It is thicker at the edges than in the middle
  4. 4. 1 — Angle of incidence
  5. 5. 35
  6. 6. Concave mirror → Converges the beam; Convex lens → Converges the beam; Convex mirror → Diverges the beam; Concave lens → Diverges the beam
  7. 7. The reflector of a torch → Concave mirror; A dentist's mirror → Concave mirror; The side-view mirror of a vehicle → Convex mirror; A road safety mirror at a bend → Convex mirror; A store's surveillance mirror → Convex mirror
  8. 8. d) Plane, concave and convex alike

Year 8 Science · www.arenapublications.com/learn