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Term pack

Grade 9 Science

Name: ________________________

Skills in this pack

  • Distance, displacement, speed and velocity
  • Motion graphs and the kinematic equations
  • Force and Newton's three laws
  • Work, energy and power
  • Inside the atom
  • How atoms combine, and what a molecule weighs
  • Sound waves
  • The cell and what is inside it
  • Plant and animal tissues
  • Reproduction: how life continues

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Grade 9 Science · 1 of 10

Distance, displacement, speed and velocity

Separate distance from displacement and speed from velocity, work out average speed, average velocity and average acceleration, and say what stays fixed in uniform circular motion.

Before you start

Slide along the track. The starting line sits at 0 and the far end at 100.

020406080100

Positions to the right of the starting line count as positive. A runner who goes out to 100 and comes back to 40 has covered a long path but ended up 40 from where she started.

  1. 1.A child on a merry-go-round rides exactly once round the circle and stops where she got on. What is the magnitude of her displacement, in meters? Answer with a number.

  2. 2.A cyclist rides round a circular track at a steady 8 m/s. What is happening to her velocity?

    • a) Its magnitude keeps changing while its direction stays fixed
    • b) Both its direction and its magnitude stay fixed
    • c) Its direction keeps changing while its magnitude stays fixed
    • d) It falls to zero each time she completes a lap

  3. 3.A bus covers 15 m in the first second, 15 m in the second and 15 m in the third. What does the chapter call this motion?

    • a) Uniform motion in a straight line
    • b) Motion with constant acceleration
    • c) Non-uniform motion in a straight line
    • d) Uniform circular motion

  4. 4.A cyclist covers 300 m of path in 60 s. What is her average speed, in m/s? Answer with a number.

  5. 5.A stone is dropped from a height. Put its speeds in order, starting from 0 m/s, at the instant it is released.

    • 29.4 m/s, after three seconds
    • 19.6 m/s, after two seconds
    • 0 m/s, at the instant it is released
    • 9.8 m/s, one second later

  6. 6.A lorry is doing 72 km/h. What is that in m/s? Answer with a number.

  7. 7.A train speeds up from 8 m/s to 20 m/s in 6 s. What is the magnitude of its average acceleration, in m/s²? Answer with a number.

  8. 8.An athlete runs along the track from O out to A, then turns and comes back as far as B. Tap the bar whose length is the magnitude of her displacement.

    Write the number of the part.

    123

Distance, displacement, speed and velocity · Grade 9 Science · www.arenapublications.com/learn

Grade 9 Science · 2 of 10

Motion graphs and the kinematic equations

Read velocity off the slope of a position-time graph and displacement off the area under a velocity-time graph, and use v = u + at, s = ut + ½at² and v² = u² + 2as.

Before you start

The parts of a position-time graph, each one named.

123
  1. 1. The time axis, along the bottom
  2. 2. The position axis, up the side
  3. 3. The position-time line itself

This line is straight and sloping, so the object is covering equal ground in equal times. How steeply it climbs is how fast it is going.

  1. 1.Three position-time graphs are sketched below. Tap the one that shows an object at rest.

    Write the number of the part.

    123

  2. 2.Put the steps for plotting a motion graph in order, starting by drawing two perpendicular axes and marking where they cross as the origin.

    • Choose a scale for each axis
    • Join the plotted points to make the graph
    • Mark the values along each axis
    • Decide which quantity goes along each axis
    • Draw two perpendicular axes and mark where they cross as the origin
    • Plot a point for each pair of readings

  3. 3.A cart starts from rest and accelerates steadily at 2 m/s² for 5 s. Use s = ut + ½at². How far does it travel, in meters? Answer with a number.

  4. 4.A child looks at a position-time graph whose line climbs steadily and says the object must have traveled uphill. What has she misread?

    • a) The graph is not a route map — its rise shows position changing with time
    • b) Nothing; a rising line does mean the object went uphill
    • c) A rising line means the object was slowing down
    • d) The graph shows velocity up the side, not position

  5. 5.When may the three kinematic equations be used?

    • a) When the velocity stays constant through the motion
    • b) When the object is at rest
    • c) For any motion whatsoever
    • d) When the acceleration stays constant through the motion

  6. 6.Sort each graph shape by what it says about the object's velocity.

    Groups: Velocity stays constant · Velocity is changing

    • A straight sloping velocity-time line
    • A velocity-time line parallel to the time axis
    • A curved position-time line
    • A straight sloping position-time line

  7. 7.On a velocity-time graph, the line runs flat and parallel to the time axis. What is the acceleration?

    • a) Constant and opposite to the direction of motion
    • b) Constant and along the direction of motion
    • c) Zero, because the velocity is not changing
    • d) Rising steadily with time

  8. 8.A van holds a steady 12 m/s for 5 s. Read the displacement off the area under its velocity-time line. How far does it go, in meters? Answer with a number.

Motion graphs and the kinematic equations · Grade 9 Science · www.arenapublications.com/learn

Grade 9 Science · 3 of 10

Force and Newton's three laws

Add forces to find the net force, use F = ma and F = mg, say what Newton's three laws claim, and treat two connected objects as one system.

Before you start

Two everyday situations, and the forces acting in each.

12
  1. 1. A box being pushed along a floor — your push one way, friction the other
  2. 2. A ball floating on water — gravity down, buoyancy up

In each case two forces oppose each other. If they match, nothing changes; if they do not, the leftover is the net force.

  1. 1.A 1500 kg car accelerates at 2 m/s². What net force is acting on it, in N? Answer with a number.

  2. 2.A fielder catching a fast ball draws his hands backwards as he takes it. Why does that help?

    • a) It stretches out the stopping time, so the acceleration and the force are both smaller
    • b) It increases the ball's acceleration, which spreads the force out
    • c) It makes the ball lighter, so less force is needed
    • d) It cancels the ball's velocity with an equal and opposite velocity

  3. 3.What is the gravitational force the Earth exerts on a 5 kg bag, in N? Answer with a number.

  4. 4.Which pair of forces is a Newton's-third-law pair?

    • a) The weight of a book and the table's upward push on that same book
    • b) The forward pull of two people pushing one stalled car
    • c) The foot pushing the ground backwards and the ground pushing the foot forwards
    • d) The push of a hand on a box and the friction on that same box

  5. 5.A block has 14 N acting on it to the right and 6 N to the left. What is the magnitude of the net force, in N? Answer with a number.

  6. 6.Boxes of 3 kg and 5 kg are joined by a string and pulled along a frictionless floor by a force of 16 N. What is the acceleration of the pair, in m/s²? Answer with a number.

  7. 7.Sort each situation by whether the forces acting are balanced.

    Groups: Balanced forces · Unbalanced forces

    • A stalled car set moving by two people pushing
    • A book lying still on a table
    • A tug of war in which both teams pull equally hard
    • A rope moving towards the team that pulls harder

  8. 8.A box slides across a floor and, once nothing is pushing it, slows down and stops. What does Newton's first law say is going on?

    • a) A moving object naturally runs out of motion and stops
    • b) Friction is a net force on the box, and it is what changes the velocity
    • c) The box stops because the push that started it has been used up
    • d) The box keeps a constant velocity, so no force can be acting

Force and Newton's three laws · Grade 9 Science · www.arenapublications.com/learn

Grade 9 Science · 4 of 10

Work, energy and power

Work out work done, kinetic energy, potential energy and power, say when work is positive, negative or zero, and explain what a pulley, a ramp and a lever actually change.

Before you start

The parts of a lever, each one named.

1234
  1. 1. The load, the weight to be lifted
  2. 2. The fulcrum, the fixed point the bar turns about
  3. 3. The effort, the push you apply
  4. 4. The load arm, from the load to the fulcrum

Put the fulcrum close to the load and the effort arm becomes long. A small push over a long distance then lifts a large load through a short one.

  1. 1.A ball of mass 0.2 kg moves at 30 m/s. What is its kinetic energy, in J? Answer with a number.

  2. 2.A lever balances with an effort of 20 N acting 60 cm from the fulcrum and the load 15 cm from it on the other side. How large is the load, in N? Answer with a number.

  3. 3.A book of mass 2 kg is raised 1.5 m above the floor. Taking g as 10 m/s², what is its potential energy, in J? Answer with a number.

  4. 4.A pump does 600 J of work in 4 s. What is its power, in W? Answer with a number.

  5. 5.A student pushes as hard as she can against a rigid wall for a minute and gets tired. How much work has she done on the wall?

    • a) None, because the wall did not move
    • b) A large amount, because she applied a large force
    • c) It cannot be worked out without knowing her mass
    • d) A small amount, because the wall moved a tiny distance

  6. 6.A force of 25 N moves a crate 4 m along the direction of the force. How much work is done on the crate, in J? Answer with a number.

  7. 7.A machine raises a load of 300 N when an effort of 100 N is applied. What is its mechanical advantage? Answer with a number.

  8. 8.A stone is dropped from a height and falls freely. What happens to its mechanical energy on the way down?

    • a) It rises, because the stone speeds up
    • b) It becomes zero the moment the stone starts moving
    • c) It stays the same, as potential energy turns into kinetic energy
    • d) It falls, because the stone loses height

Work, energy and power · Grade 9 Science · www.arenapublications.com/learn

Grade 9 Science · 5 of 10

Inside the atom

Count protons, neutrons and electrons from an atomic number and a mass number, fill the shells and read off a valency, and say what makes two atoms isotopes.

Before you start

The parts of an atom, each one named.

1234
  1. 1. The center
  2. 2. The nearest ring
  3. 3. The middle ring
  4. 4. The furthest ring

The center is the nucleus, holding the protons and neutrons. The rings are the shells, filled from the inside out: K first, then L, then M.

  1. 1.Nitrogen's electronic configuration is 2, 5. What is its valency? Answer with a number.

  2. 2.An atom of atomic number 26 has 56 nucleons. How many neutrons has it? Answer with a number.

  3. 3.Match each element to its symbol.

    • Iron
    • Sodium
    • Potassium
    • Silver
    • Gold
    • Ag
    • Na
    • K
    • Fe
    • Au

  4. 4.Put the shells in the order electrons fill them, starting from The K shell, nearest the nucleus.

    • The M shell
    • The L shell
    • The K shell, nearest the nucleus
    • The N shell

  5. 5.Oxygen's electronic configuration is 2, 6. What is its valency? Answer with a number.

  6. 6.Why do the isotopes of an element behave the same way chemically?

    • a) They have the same melting and boiling points
    • b) They have the same number of electrons, arranged the same way
    • c) They have the same mass number
    • d) They have the same number of neutrons

  7. 7.An atom has 17 protons and 18 neutrons. What is its mass number? Answer with a number.

  8. 8.Using the rule that a shell numbered n holds at most 2n² electrons, what is the greatest number the M shell, where n is 3, can hold? Answer with a number.

Inside the atom · Grade 9 Science · www.arenapublications.com/learn

Grade 9 Science · 6 of 10

How atoms combine, and what a molecule weighs

Use the laws of conservation of mass and of constant proportions, tell a covalent bond from an ionic one, write a formula by crossing over valencies, and add up a molecular or formula unit mass.

Before you start

A sodium atom beside a chlorine atom, with each shell named.

1234
  1. 1. Sodium's inner shells, holding 2 then 8 electrons
  2. 2. Sodium's valence shell, holding its single electron
  3. 3. Chlorine's inner shells, holding 2 then 8 electrons
  4. 4. Chlorine's valence shell, holding 7 electrons

Sodium has one electron more than a full inner arrangement; chlorine is one short of eight. Hand the electron across and both are satisfied — that is an ionic bond in one move.

  1. 1.Sort each substance by the kind of bond holding it together.

    Groups: Held together by sharing electrons · Held together by transferring electrons

    • Hydrogen molecule
    • Sodium chloride
    • Magnesium oxide
    • Chlorine molecule

  2. 2.A reaction is carried out in a sealed flask on a balance. What does the Law of Conservation of Mass predict about the reading?

    • a) It rises, because new substances have been made
    • b) It falls, because some matter is used up
    • c) It cannot be predicted without knowing the products
    • d) It is the same before and after the reaction

  3. 3.A sodium atom, with 11 protons and 11 electrons, loses its single valence electron. What is it now?

    • a) An anion, carrying one negative charge
    • b) A different element, since its proton count changed
    • c) A cation, carrying one positive charge
    • d) Still a neutral atom, since electrons carry no charge

  4. 4.Taking K as 39 u and Cl as 35.5 u, what is the formula unit mass of potassium chloride, KCl, in u? Answer with a number.

  5. 5.Why is sodium chloride described by a formula unit mass rather than a molecular mass?

    • a) Its ions form a crystal rather than separate molecules
    • b) Its formula has more than one kind of atom in it
    • c) Its atoms share electrons instead of transferring them
    • d) It is too heavy for a molecular mass to be worked out

  6. 6.Which of these describes a molecule, as the chapter defines it?

    • a) A single atom of any element
    • b) A charged particle formed when an atom gains an electron
    • c) An electrically neutral group of more than one atom that can exist on its own
    • d) The simplest whole-number ratio of ions in a crystal

  7. 7.Hydrogen and oxygen combine to make water in the mass ratio 1 to 8. What mass of oxygen combines with 3 g of hydrogen, in g? Answer with a number.

  8. 8.Taking H as 1 u, N as 14 u and O as 16 u, what is the molecular mass of nitric acid, HNO3, in u? Answer with a number.

How atoms combine, and what a molecule weighs · Grade 9 Science · www.arenapublications.com/learn

Grade 9 Science · 7 of 10

Sound waves

Say why sound needs a medium, use v = λν and ν = 1/T, work out an echo distance, and place a frequency in the infrasonic, audible or ultrasonic band.

Before you start

Two sound waves, drawn one above the other.

12
  1. 1. The quieter wave — a small change in density, so less energy
  2. 2. The louder wave — a large change in density, so more energy

The two waves rise and fall the same number of times across the page, so they share a wavelength and a frequency. What differs is how far the density swings from its average — the amplitude.

  1. 1.Sort each description by the band of frequency it belongs to.

    Groups: Infrasonic · Audible to humans · Ultrasonic

    • Bursts a bat sends out to find its prey
    • Waves used to image internal organs without surgery
    • Between 20 hertz and 20 kilohertz
    • Below 20 hertz
    • Above 20 kilohertz
    • Waves used to detect earthquakes and volcanic eruptions

  2. 2.A metal plate is struck harder than before. What changes in the sound wave it sends out?

    • a) Its amplitude is larger, so it carries more energy
    • b) Its time period is longer, so it carries more energy
    • c) Its wavelength is larger, so it carries more energy
    • d) Its speed is greater, so it carries more energy

  3. 3.Match each quantity to the unit it is measured in.

    • Wavelength
    • Frequency
    • Time period
    • Speed of sound
    • meter per second
    • hertz
    • second
    • meter

  4. 4.A wave has a time period of 0.02 s. What is its frequency, in Hz? Answer with a number.

  5. 5.A tuning fork is struck across the room. What reaches your ear?

    • a) Small pieces of the fork itself
    • b) The air particles that were next to the fork
    • c) A stream of compressed air from the fork
    • d) Energy carried by the sound wave

  6. 6.A sound wave is drawn as density against distance, with the middle line marking the average density. Tap the span that is one wavelength.

    Write the number of the part.

    123

  7. 7.In a large hall a sound seems to hang in the air after the speaker has stopped. What is that called, and what causes it?

    • a) An echo, from a single reflection arriving more than 0.1 s later
    • b) Refraction, from the sound bending round the pillars
    • c) Resonance, from the hall matching the speaker's frequency
    • d) Reverberation, from repeated reflections arriving less than 0.05 s apart

  8. 8.Two astronauts float side by side in the near-vacuum of space and clank two metal tools together. What happens?

    • a) Both hear it, but faintly and after a long delay
    • b) Just the astronaut holding the tools hears it, through her gloves
    • c) Both hear it, because a vacuum lets sound through freely
    • d) Neither hears it directly, because sound needs a medium

Sound waves · Grade 9 Science · www.arenapublications.com/learn

Grade 9 Science · 8 of 10

The cell and what is inside it

Name the parts of a plant and an animal cell and say what each does, tell a prokaryotic cell from a eukaryotic one, and use osmosis to explain what happens to a cell in salty water.

Before you start

The parts of a cell, each one named.

1234
  1. 1. The round body with a smaller body inside it — the nucleus
  2. 2. The rod with folded lines inside — a mitochondrion
  3. 3. The large clear space — the vacuole
  4. 4. The stack of folded sheets — the endoplasmic reticulum

The outline round the whole thing is the cell membrane. On a plant cell there would be a stiffer layer of cellulose outside it again, and green ovals of chloroplast among the organelles.

  1. 1.A Rhoeo leaf peel is mounted in a strong sugar solution. Its cells lose water, yet the outline of each cell stays the same shape. What accounts for that?

    • a) The chloroplasts stiffen and hold the cell out
    • b) The vacuole refills from the sugar solution as fast as water leaves
    • c) Plant cells cannot lose water through their membranes
    • d) The rigid cell wall holds the outer shape while the membrane pulls inwards

  2. 2.Match each organelle to the job it does in the cell.

    • Ribosome
    • Golgi apparatus
    • Lysosome
    • Mitochondrion
    • Chloroplast
    • Releasing the energy a cell runs on
    • Making food using sunlight
    • Packing materials into vesicles for transport
    • Where proteins are made
    • Breaking down waste and worn-out parts

  3. 3.Sort each feature by the kind of cell it belongs to.

    Groups: Prokaryotic cell · Eukaryotic cell

    • Membrane-bound nucleus
    • Genetic material in a bare nucleoid
    • Membrane-bound organelles
    • A typical width of 1 to 10 micrometres
    • A typical width of 10 to 100 micrometres

  4. 4.What is the one-word name for the movement of water across a selectively permeable membrane?

  5. 5.Which statement is part of the classical cell theory?

    • a) New cells can form from non-living matter under the right conditions
    • b) Cells are found in animals but not in plants
    • c) New cells arise from cells that already exist
    • d) The tissue, not the cell, is the basic unit of function

  6. 6.Put the journey of a protein that is going to be secreted into order, starting from A ribosome on the rough endoplasmic reticulum makes the protein.

    • The Golgi apparatus packs it into a vesicle
    • The Golgi apparatus modifies and sorts it
    • A ribosome on the rough endoplasmic reticulum makes the protein
    • The vesicle carries it out to the cell membrane
    • The rough endoplasmic reticulum passes it on

  7. 7.What is a plant cell wall built mainly from?

    • a) Cellulose
    • b) Lipid
    • c) Protein
    • d) Starch

  8. 8.Who examined a thin slice of cork in 1665 and gave the little compartments he saw the name we still use? Give the surname.

The cell and what is inside it · Grade 9 Science · www.arenapublications.com/learn

Grade 9 Science · 9 of 10

Plant and animal tissues

Name the three meristems and the permanent tissues they become, match each plant and animal tissue to its job, and tell the joints and muscle types apart by what they do.

Before you start

Three simple permanent tissues, side by side and each one named.

123
  1. 1. Thin walls the whole way round — parenchyma
  2. 2. Corners thickened with pectin — collenchyma
  3. 3. Thick lignified walls — sclerenchyma

Parenchyma is alive and stores food. Collenchyma is alive and bends. Sclerenchyma is mostly dead cells, and it is what makes a coconut husk hard.

  1. 1.Match each plant tissue to the job it does.

    • Xylem
    • Phloem
    • Epidermis
    • Sclerenchyma
    • Collenchyma
    • Carries water and minerals up from the roots
    • Carries food from the leaves to the rest of the plant
    • Supports a part while letting it bend
    • Forms the outer protective layer
    • Makes a part hard and strong with lignified walls

  2. 2.Sort each of these by the kind of joint it is.

    Groups: Ball and socket joint · Hinge joint · Pivot joint · Fixed joint

    • Shoulder
    • Knee
    • Elbow
    • Neck, where the skull meets the backbone
    • Bones of the skull

  3. 3.How many pairs of ribs make up the human rib cage? Answer with a number.

  4. 4.Put a message's journey through a neuron in order, starting from The dendrites pick the message up from another neuron.

    • The cell body, which holds the nucleus, takes it in
    • The dendrites pick the message up from another neuron
    • The axon carries it away as a long fiber
    • The axon terminals pass it on to the next cell

  5. 5.A lawn is mown short and grows back bushy within a fortnight. Which meristem accounts for that?

    • a) The lateral meristem, in a ring inside the stem
    • b) The apical meristem, at the shoot tips
    • c) No meristem — the old leaves simply stretch
    • d) The intercalary meristem, at the base of the internodes

  6. 6.This is a neuron. Tap the part that picks up signals coming from other neurons.

    Write the number of the part.

    1234

  7. 7.Which simple permanent tissue has thick walls stiffened with lignin and is made mostly of dead cells?

    • a) Epidermis
    • b) Collenchyma
    • c) Parenchyma
    • d) Sclerenchyma

  8. 8.What are the pores in a leaf's epidermis called? Give the one word.

Plant and animal tissues · Grade 9 Science · www.arenapublications.com/learn

Grade 9 Science · 10 of 10

Reproduction: how life continues

Tell asexual reproduction from sexual, name the parts of a flower and follow pollen through to a seed, and describe fertilization and the reproductive cycle in animals and humans.

Before you start

The parts of a flower, each one named.

123456
  1. 1. The green flap at the base — a sepal
  2. 2. The broad flap sweeping out to the side — a petal
  3. 3. The small sac on the end of the slender stalk — the anther of a stamen
  4. 4. The flattened cap on top of the central column — the stigma
  5. 5. The thin central column — the style
  6. 6. The rounded swelling at the base of the column — the ovary

Sepals and petals are the two outer whorls. The stamen is the male part and the pistil — stigma, style and ovary together — is the female one.

  1. 1.A frog lays thousands of eggs in a pond while a bird lays a handful in a nest. What does the chapter say about the two strategies?

    • a) The frog's fertilization is internal and the bird's external
    • b) Both fertilize internally, and the difference lies in nest-building
    • c) Survival is the same in both; the frog simply lays more
    • d) The frog's fertilization is external and survival is low; the bird's is internal and survival is better

  2. 2.Tap the part of this flower that produces the pollen grains.

    Write the number of the part.

    123456

  3. 3.A gardener grows twenty plants from cuttings of one rose bush. How do the new plants compare with the parent?

    • a) They vary from it, because cuttings mix genetic material from two parents
    • b) They are genetically identical to it, because one parent and mitosis were involved
    • c) They vary, because meiosis takes place when a cutting roots
    • d) They are identical to each other but different from the parent

  4. 4.Sort each case by the kind of reproduction it is.

    Groups: Asexual reproduction · Sexual reproduction

    • A male gamete from a pollen grain fusing with an egg cell
    • A gardener rooting a sugarcane stem cutting
    • A frog releasing eggs into water for a male to fertilize
    • A Bryophyllum leaf sprouting tiny plantlets
    • A potato sprouting new plants from its underground stem

  5. 5.What is the one-word name for the transfer of pollen grains from a stamen to a stigma?

  6. 6.In a butterfly's development, which stage is described as the feeding stage that gathers the nutrition the adult body is built from?

    • a) The adult
    • b) The larva
    • c) The egg
    • d) The pupa

  7. 7.A flower is fertilized. What becomes of the ovary?

    • a) It falls away once the seeds are formed
    • b) It enlarges and develops into the fruit
    • c) It grows into the pollen tube
    • d) It becomes the seed, while the ovules become the fruit

  8. 8.Match each part of a flower to what it does.

    • Anther
    • Stigma
    • Style
    • Ovary
    • Sepal
    • Connects the stigma down to the ovary
    • Holds the ovules and becomes the fruit
    • Receives the pollen
    • Produces the pollen grains
    • Protects the flower while it is in bud

Reproduction: how life continues · Grade 9 Science · www.arenapublications.com/learn

Answer keys — Grade 9 Science

In the same order as the worksheets.

Distance, displacement, speed and velocity

  1. 1. 0
  2. 2. c) Its direction keeps changing while its magnitude stays fixed
  3. 3. a) Uniform motion in a straight line
  4. 4. 5
  5. 5. 1. 0 m/s, at the instant it is released 2. 9.8 m/s, one second later 3. 19.6 m/s, after two seconds 4. 29.4 m/s, after three seconds
  6. 6. 20
  7. 7. 2
  8. 8. 3 — The stretch from O to B

Motion graphs and the kinematic equations

  1. 1. 1 — The first graph, a flat line
  2. 2. 1. Draw two perpendicular axes and mark where they cross as the origin 2. Decide which quantity goes along each axis 3. Choose a scale for each axis 4. Mark the values along each axis 5. Plot a point for each pair of readings 6. Join the plotted points to make the graph
  3. 3. 25
  4. 4. a) The graph is not a route map — its rise shows position changing with time
  5. 5. d) When the acceleration stays constant through the motion
  6. 6. A straight sloping position-time line → Velocity stays constant; A velocity-time line parallel to the time axis → Velocity stays constant; A curved position-time line → Velocity is changing; A straight sloping velocity-time line → Velocity is changing
  7. 7. c) Zero, because the velocity is not changing
  8. 8. 60

Force and Newton's three laws

  1. 1. 3000
  2. 2. a) It stretches out the stopping time, so the acceleration and the force are both smaller
  3. 3. 49
  4. 4. c) The foot pushing the ground backwards and the ground pushing the foot forwards
  5. 5. 8
  6. 6. 2
  7. 7. A tug of war in which both teams pull equally hard → Balanced forces; A book lying still on a table → Balanced forces; A rope moving towards the team that pulls harder → Unbalanced forces; A stalled car set moving by two people pushing → Unbalanced forces
  8. 8. b) Friction is a net force on the box, and it is what changes the velocity

Work, energy and power

  1. 1. 90
  2. 2. 80
  3. 3. 30
  4. 4. 150
  5. 5. a) None, because the wall did not move
  6. 6. 100
  7. 7. 3
  8. 8. c) It stays the same, as potential energy turns into kinetic energy

Inside the atom

  1. 1. 3
  2. 2. 30
  3. 3. Iron → Fe; Sodium → Na; Potassium → K; Silver → Ag; Gold → Au
  4. 4. 1. The K shell, nearest the nucleus 2. The L shell 3. The M shell 4. The N shell
  5. 5. 2
  6. 6. b) They have the same number of electrons, arranged the same way
  7. 7. 35
  8. 8. 18

How atoms combine, and what a molecule weighs

  1. 1. Hydrogen molecule → Held together by sharing electrons; Chlorine molecule → Held together by sharing electrons; Sodium chloride → Held together by transferring electrons; Magnesium oxide → Held together by transferring electrons
  2. 2. d) It is the same before and after the reaction
  3. 3. c) A cation, carrying one positive charge
  4. 4. 74.5
  5. 5. a) Its ions form a crystal rather than separate molecules
  6. 6. c) An electrically neutral group of more than one atom that can exist on its own
  7. 7. 24
  8. 8. 63

Sound waves

  1. 1. Below 20 hertz → Infrasonic; Waves used to detect earthquakes and volcanic eruptions → Infrasonic; Between 20 hertz and 20 kilohertz → Audible to humans; Above 20 kilohertz → Ultrasonic; Waves used to image internal organs without surgery → Ultrasonic; Bursts a bat sends out to find its prey → Ultrasonic
  2. 2. a) Its amplitude is larger, so it carries more energy
  3. 3. Wavelength → meter; Frequency → hertz; Time period → second; Speed of sound → meter per second
  4. 4. 50
  5. 5. d) Energy carried by the sound wave
  6. 6. 1 — The span from one crest across to the next crest
  7. 7. d) Reverberation, from repeated reflections arriving less than 0.05 s apart
  8. 8. d) Neither hears it directly, because sound needs a medium

The cell and what is inside it

  1. 1. d) The rigid cell wall holds the outer shape while the membrane pulls inwards
  2. 2. Ribosome → Where proteins are made; Golgi apparatus → Packing materials into vesicles for transport; Lysosome → Breaking down waste and worn-out parts; Mitochondrion → Releasing the energy a cell runs on; Chloroplast → Making food using sunlight
  3. 3. Genetic material in a bare nucleoid → Prokaryotic cell; A typical width of 1 to 10 micrometres → Prokaryotic cell; Membrane-bound organelles → Eukaryotic cell; Membrane-bound nucleus → Eukaryotic cell; A typical width of 10 to 100 micrometres → Eukaryotic cell
  4. 4. osmosis
  5. 5. c) New cells arise from cells that already exist
  6. 6. 1. A ribosome on the rough endoplasmic reticulum makes the protein 2. The rough endoplasmic reticulum passes it on 3. The Golgi apparatus modifies and sorts it 4. The Golgi apparatus packs it into a vesicle 5. The vesicle carries it out to the cell membrane
  7. 7. a) Cellulose
  8. 8. Hooke

Plant and animal tissues

  1. 1. Xylem → Carries water and minerals up from the roots; Phloem → Carries food from the leaves to the rest of the plant; Epidermis → Forms the outer protective layer; Sclerenchyma → Makes a part hard and strong with lignified walls; Collenchyma → Supports a part while letting it bend
  2. 2. Shoulder → Ball and socket joint; Elbow → Hinge joint; Knee → Hinge joint; Neck, where the skull meets the backbone → Pivot joint; Bones of the skull → Fixed joint
  3. 3. 12
  4. 4. 1. The dendrites pick the message up from another neuron 2. The cell body, which holds the nucleus, takes it in 3. The axon carries it away as a long fiber 4. The axon terminals pass it on to the next cell
  5. 5. d) The intercalary meristem, at the base of the internodes
  6. 6. 1 — The branching fibers on the left
  7. 7. d) Sclerenchyma
  8. 8. stomata

Reproduction: how life continues

  1. 1. d) The frog's fertilization is external and survival is low; the bird's is internal and survival is better
  2. 2. 3 — The small sac on the end of the slender stalk
  3. 3. b) They are genetically identical to it, because one parent and mitosis were involved
  4. 4. A potato sprouting new plants from its underground stem → Asexual reproduction; A Bryophyllum leaf sprouting tiny plantlets → Asexual reproduction; A gardener rooting a sugarcane stem cutting → Asexual reproduction; A male gamete from a pollen grain fusing with an egg cell → Sexual reproduction; A frog releasing eggs into water for a male to fertilize → Sexual reproduction
  5. 5. pollination
  6. 6. b) The larva
  7. 7. b) It enlarges and develops into the fruit
  8. 8. Anther → Produces the pollen grains; Stigma → Receives the pollen; Style → Connects the stigma down to the ovary; Ovary → Holds the ovules and becomes the fruit; Sepal → Protects the flower while it is in bud

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