Contents
Enquiry processes
1
2
3
2
4
6
Asking scientific questions
Planning investigations
Recording data
1: Forces
12
Introduction to forces
Balanced and unbalanced
Speed
Distance–time graphs
14
16
18
20
Potential difference
Resistance
Series and parallel circuits
2.2 Current
28
30
32
4: Waves
3.2 Energy transfer
42
44
46
ii
48
50
52
54
4.2 Light
56
58
60
62
4.2.1
Light
4.2.2
Reflection
4.2.3
Refraction
4.2.4
The eye and vision
4.2.5
Colour
Part 1 Summary and Questions
The particle model
States of matter
Melting and freezing
Boiling
More changes of state
Diffusion
Gas pressure
Inside particles
64
66
68
70
72
74
76
Part 1 Opener
5.1 Particle model
5.1.1
5.1.2
5.1.3
5.1.4
5.1.5
5.1.6
5.1.7
5.1.8
3.2.1
Energy adds up
3.2.2
Energy dissipation
Part 1 Summary and Questions
Part 1 Opener
Sound waves and speed
Loudness and amplitude
Frequency and pitch
The ear and hearing
5: Matter
34
36
38
40
4.1 Sound
4.1.1
4.1.2
4.1.3
4.1.4
2.2.1 Current
2.2.2 Charging up
Part 1 Summary and Questions
Part 1 Opener
Food and fuels
Energy resources
Energy and power
22
24
26
3.1 Energy costs
3.1.1
3.1.2
3.1.3
1.2.1 Gravity
Part 1 Summary and Questions
Part 1 Opener
2.1 Potential difference and resistance
3: Energy
8
10
1.2 Gravity
2: Electromagnets
2.1.1
2.1.2
2.1.3
Analysing patterns
Evaluating data
Part 1 Opener
1.1 Speed
1.1.1
1.1.2
1.1.3
1.1.4
4
5
5.2 Separating mixtures
78
80
82
84
86
88
90
92
5.2.1 Pure substances and mixtures
5.2.2 Solutions
5.2.3 Solubility
5.2.4 Filtration
5.2.5 Evaporation and distillation
5.2.6 Chromatography
Part 1 Summary and Questions
94
96
98
100
102
104
106
6: Reactions
108
Part 1 Opener
6.1 Acids and alkalis
6.1.1
6.1.2
6.1.3
6.1.4
6.1.5
6.1.6
Chemical reactions
Acids and alkalis
Indicators and pH
Acid strength
Neutralisation
Making salts
7: Earth
6.2 Metals and non-metals
110
112
114
116
118
120
136
Part 1 Opener
7.1 Earth structure
7.1.1
7.1.2
7.1.3
7.1.4
7.1.5
The structure of the Earth
Sedimentary rocks
Igneous and metamorphic rocks
The rock cycle
Ceramics
8: Organisms
7.2 Universe
138
140
142
144
146
158
160
162
164
166
Food chains and webs
Disruption to food chains and webs
Ecosystems
Competition
9.2 Plant reproduction
182
184
186
188
9.2.1 Flowers and pollination
9.2.2 Fertilisation and germination
9.2.3 Seed dispersal
Part 1 Summary and Questions
190
192
194
196
198
Part 1 Opener
10.1.1 Variation
10.1.2 Continuous and discontinuous
10.1.3 Adapting to change
168
170
172
174
176
178
180
10.1 Variation
Glossary
Index
8.2.1 Observing cells
8.2.2 Plant and animal cells
8.2.3 Specialised cells
8.2.4 Movement of substances
8.2.5 Uni-cellular organisms
Part 1 Summary and Questions
Part 1 Opener
9.1 Interdependence
10: Genes
148
150
152
154
156
8.2 Cells
Levels of organisation
The skeleton
Movement: joints
Movement: muscles
9: Ecosystems
9.1.1
9.1.2
9.1.3
9.1.4
7.2.1 The night sky
7.2.2 The Solar System
7.2.3 The Earth
7.2.4 The Moon and changing ideas
Part 1 Summary and Questions
Part 1 Opener
8.1 Movement
8.1.1
8.1.2
8.1.3
8.1.4
6.2.1 More about elements
122
6.2.2 Chemical reactions of metals and non-metals 124
6.2.3 Metals and acids
126
6.2.4 Metals and oxygen
128
6.2.5 Metals and water
130
6.2.6 Metal displacement reactions
132
Part 1 Summary and Questions
134
10.2 Human reproduction
200
202
204
10.2.1 Adolescence
10.2.2 Reproductive systems
10.2.3 Fertilisation and implantation
10.2.4 Development of a fetus
10.2.5 The menstrual cycle
Part 1 Summary and Questions
206
208
210
212
214
216
218
228
iii
3.1.3
Energy and power
Learning objectives
After this section you will be able to:
●
●
●
describe what you pay for when
you pay your electricity bill
calculate the cost for home
energy usage
compare the energy usage
and cost of running different
home devices.
Fantastic Fact
When you make popcorn you are boiling
water. The water inside the popcorn kernel
turns to steam and it explodes.
Some microwaves cook popcorn faster than others. Why
is there a difference?
Microwave ovens have a power rating in watts (W). The power
rating tells you how much energy is transferred per second–the rate
of transfer of energy.
You can calculate power using this formula:
power (W) =
energy (J)
time (s)
The power of a microwave oven is about 800 W. A traditional oven
has a power of about 2500 W, or 2.5 kilowatts.
Most of the heating appliances in your house will have a rating in
kilowatts. Light bulbs have a rating in watts.
Kilowatts and kilojoules
12 000 W is the same as 12 kilowatts, or 12 kW. There are 1000 W
in 1 kW. You divide by 1000 to convert watts to kilowatts.
An oven with a rating of 2.5 kW transfers energy at a rate of
2500 J per second. This is the same as 12 kilojoules per second.
There are 1000 J in 1 kJ.
A State the unit of power.
The power rating of this appliance is
2000 W.
Keeping the temperature the same
All hot objects cool down. To keep a house at the same
temperature you need to transfer energy to it at the same rate as
energy is being transferred from it.
What are you paying for?
When you pay an electricity bill, you are usually paying for a fuel
such as coal to be burnt in a power station. The power station
generates the potential difference that we call ‘mains electricity’.
You are charged for the number of hours that you use each
appliance and for the power of the appliance.
46
Some houses transfer more energy to
the surroundings than others.
You can calculate energy use in kilowatt hours (kWh) or joules.
This is the unit that electricity companies use to calculate your bill.
Big Idea: Energy 3
You can calculate the cost of using appliances at home using
the formula:
cost = power (kW) × time (hours) × price (per kWh)
Suppose you use a 2.5 kW oven for 2 hours. Each kWh costs 10p.
cost = 2.5 kW × 2 hours × 10 p/kWh
= 50 p
B State the unit of energy that electricity companies use.
To reduce your energy bills you could use fewer appliances or
appliances that require less power to produce the same output. You
can also use appliances for fewer hours. Insulation reduces the rate
at which energy is transferred to the surroundings, so it reduces the
rate at which you need to supply energy to heat the house.
The electricity meter shows how
much energy you have used in kWh.
Governments can raise awareness about energy use to try to make
fossil fuels last longer. This would also benefit the environment.
Summary Questions
1 Copy and complete the
sentences below.
Energy is measured in
and
.
power is measured in
Power is the energy transferred per
. You pay for the number of
that are transferred to your
house by electricity. You could
save money by using appliances
power rating or by
with a
time.
using them for
The bulbs are the same brightness but the one on the right has a
much lower power.
What’s the cost?
A shower has a power of 10 kW. A family uses the shower for
1 hour per day.
a Calculate how much energy, in kilowatt hours, they would
have to pay for each week for using the shower.
b An electricity company charges 10p for each kWh. Calculate
the cost in pounds.
Key Words
watt, power, kilowatt, kilowatt hour
(6 marks)
2
Compare the cost of using a
kettle with a power rating of 2 kW
and a kettle rated 1.2 kW.
(6 marks)
3
a Suggest a measure that a
government can take to reduce
a country’s energy use. (1 mark)
b Suggest reasons why the
campaign may be successful.
(1 mark)
Topic 3.1 Energy costs
47
3.2.1
Energy adds up
Learning objectives
After this section you will be able to:
●
●
●
use a model of energy transfer
between stores to describe how
jobs get done
describe how the energy of an
object depends on its speed,
temperature, height, or whether
it is stretched or compressed
show how energy is transferred
between energy stores in a
range of real-life examples.
Energy is a bit
like money.
Do you have some money in your pocket? If you know
how much you left home with and you didn’t spend any
on the way, then you know how much you have now.
Conservation of energy
Energy cannot just disappear, and you cannot end up with more
than you had at the start. Energy cannot be created or destroyed,
only transferred. This is the law of conservation of energy.
A State the law of conservation of energy.
Energy stores
There is energy associated with food and fuels (and oxygen). You
can think of that energy as being in a chemical energy store.
Energy is transferred from the store when you burn the fuel or
respire. There are other types of energy store:
Energy to do with…
Type of energy store
food, fuels, batteries
chemical energy store
hot objects
thermal energy store
moving objects
kinetic energy store
position in a gravitational field
gravitational potential energy store
changing shape, stretching, or squashing
elastic energy store
Before and after
A camping stove burns gas, which is a fuel.
Before:
After:
What we
have
unburnt fuel, more oxygen
cold soup
less fuel, more carbon dioxide
and water
hot soup (and slightly hotter air)
Thinking
about
energy
more energy in the chemical
energy store
less energy in the thermal
energy store
less energy in the chemical
energy store
more energy in the thermal
energy store
If you could measure the energy in the chemical and thermal
energy stores you would see that:
total energy before = total energy after
48
B Name five types of energy store.
Camping gas is a chemical store.
Big Idea: Energy 3
Transferring energy
Electric current, radiation (like light), waves (like sound), and
heating are ways of transferring energy between stores. After you
use your phone, there is less energy in the chemical energy store
and more energy in the thermal energy store of the surroundings.
C State three ways that energy is transferred between stores.
Driving at a steady speed
When you are driving along the motorway at 70 m.p.h. you might
think that there is energy going into a kinetic energy store. If your
speed is not changing, then the energy in the kinetic store is not
changing either. Here is an analysis:
Before
After
What we
have
colder car and surroundings,
more petrol and oxygen, less
carbon dioxide and water
warmer car and surroundings,
less petrol and oxygen, more
carbon dioxide and water
Thinking
about
energy
more energy in the chemical energy
store of the petrol and oxygen
less energy in the thermal energy
stores of the car and surroundings
less energy in the chemical energy
store of the petrol and oxygen
more energy in the thermal energy
stores of the car and surroundings
Fantastic Fact
If all the energy in the food that you eat was
converted to energy in a thermal energy
store, you would glow like a light bulb.
Key Words
law of conservation of energy, chemical
energy store, thermal energy store, kinetic
energy store, gravitational potential
energy store, elastic energy store
Summary Questions
1 Copy and complete the
sentences below, choosing the
correct bold words.
The law of conservation of energy
says that energy cannot be
created/transferred or
destroyed/transferred. When you
burn coal, you transfer energy from
a chemical/thermal energy store to
a chemical/thermal energy store.
You can/cannot explain why things
happen using energy.
(5 marks)
Bouncing a ball
When you bounce a ball it doesn't bounce as high. What is
happening in terms of energy?
Before
After
What we
have
ball lifted up, cooler ball and
surroundings
ball at the top of the first bounce,
warmer ball and surroundings
Thinking
about
energy
more energy in the gravitational
potential energy store of the ball
less energy in the thermal energy
stores of the ball and surroundings
less energy in the gravitational
potential energy store of the ball
more energy in the thermal energy
stores of the ball and surroundings
2
Describe in terms of energy
stores and transfers what happens
when you:
a use a torch
b generate electricity using coal
to run a cooker
c generate electricity using wind
to run a motor.
(6 marks)
3
Cars on a motorway are
heating the surroundings.
When a ball bounces, it heats
the air and the ground.
Remember those stores!
Use the first letter of each of the stores in the table above to
write a mnemonic to help you to remember them.
4
Describe how the energy
store of an object is linked to its
speed, temperature, height, and
compression.
(1 mark)
Use the ideas on these
two pages to explain in detail what
energy transfers happen when you
cook sausages on a camp fire
burning wood.
(6 marks)
Topic 3.2 Energy transfer
49
3.2.2
Energy dissipation
Learning objectives
After this section you will be able to:
●
●
●
describe what dissipation
means
calculate the useful energy
and the amount dissipated,
given values of input and
output energy
explain how energy is dissipated
in a range of situations.
What does it mean to ‘save energy’? If energy is
conserved, how can it be saved?
Wasting energy
When you travel in a car you want the fuel that you burn to produce
an increase in energy in the store that you want (your accelerating
car), not in the energy store that you don’t (a hot engine).
The useful energy is in a kinetic energy store, and the wasted
energy is in a thermal energy store.
Engineers have improved car design to reduce energy transferred
to the surroundings.
Here are two situations where energy transfers to both useful and
wasted energy stores.
Situation
A car engine gets very hot.
Link
You will learn more about energy
transfers in Book 2, 3.4.2 Energy transfer:
particles and Book 2, 3.4.3 Energy
transfer: radiation and insulation.
Key Word
dissipation
Fantastic Fact
50
When it comes back to Earth, air
resistance from the atmosphere heats up
the outside of a space vehicle to several
thousand degrees Celsius.
Energy in this store
decreases
Useful energy in
this store increases
Wasted energy in
this store increases
car
chemical energy store
accelerating of the fuel (petrol) and
oxygen
kinetic energy store
of the accelerating
car
thermal energy
store of the
surroundings
using a
toaster
chemical energy store of thermal energy
store of the toast
the fuel (coal at power
station) and oxygen
thermal energy
store of the
surroundings
When you are driving a car, energy is transferred to the thermal
store of the surroundings. The air or ground heats up a bit. That is
not useful. You cannot transfer that energy to another store that you
want it to go to, so it is effectively ’wasted’. In that case, scientists say
that energy is dissipated.
A What does ‘dissipation’ mean?
Why is energy dissipated, and how can you
reduce dissipation?
In a car, you want all the energy in the chemical energy store of the
fuel and oxygen to end up in the kinetic energy store. This does not
happen because of the contact forces acting on the car. Air resistance
Big Idea: Energy 3
acts on the car as it moves through the air. Friction acts between
engine parts and between the car and the road. These processes
transfer energy to the thermal energy store of the surroundings.
B Name two ways to reduce dissipation in a car.
When you buy an appliance a label
should tell you how efficient the
appliance is.
We say things ‘burn up’ in the atmosphere. We mean that the force
of air resistance has a large heating effect. When bits of rock hit
the atmosphere we see a meteor shower.
Energy is not just dissipated by contact forces.
●
●
●
Friction between surfaces can make them vibrate, producing
sound.
When a current flows in a wire, the wire gets hot. This transfers
energy to the thermal energy store of the surroundings. You
can reduce the energy dissipated by reducing the resistance of
the wires.
When objects get hot, they transfer energy to anything around
them that is at a lower temperature. You can reduce dissipation
by using insulation.
A ball loses energy each time it
bounces.
Summary Questions
1 Copy and complete the sentences
below by choosing the correct words:
Energy can be transferred to the
surroundings or to other places
that we do not want by
, such as air resistance or
. When this happens we say
.
that energy is wasted, or
What is efficiency?
You can show how much energy is transferred usefully, and how
much is wasted, using the idea of efficiency.
efficiency useful energy output × 100
=
(%)
energy input
For example, if the energy transferred from the chemical energy store
of the fuel and oxygen in a car is 100 J and only 40 J is transferred to
the kinetic energy store of the car, then the engine is 40% efficient.
(3 marks)
2
a A kettle transfers 200 J of energy
to the thermal energy store of
the water in it for every 500 J of
input energy. Calculate the
wasted energy.
(2 marks)
The wasted energy, or energy dissipated
= energy input – useful energy output
= 100 J – 40 J
= 60 J
Wasting energy
You may have heard people say that it is important to save energy.
But if energy is conserved, how can you save it? You aren’t really
saving energy. You are saving fuel. There is less wasted energy, so
you need to use less fuel to do the job that you want.
b Calculate the efficiency of
the kettle.
(2 marks)
3
Compare the conservation
of energy and the dissipation of
energy, and explain the link
between the two.
(6 marks)
Topic 3.2 Energy transfer
51
3 Energy: Summary
Key Points
Energy costs
● There is energy associated with food and fuels. Energy is measured in
joules, J.
● Fossil fuels are non-renewable energy resources used for heating,
transportation, and generating electricity.
● Renewable energy resources can also be used to generate electricity.
● Power tells you how quickly energy is transferred by a device. You can
calculate power using the formula: power (W) = energy (J) .
time (s)
● You can work out the cost of the energy transferred by appliances in your home using
the formula: cost = power (kW) x time (hours) x price (kWh). Energy companies use
the unit of kilowatt hours.
Energy transfer
● Energy cannot be created or destroyed, it can only be transferred between stores. This is
the law of conservation of energy. An energy store is a way of keeping track of energy.
● Radiation (like light), heating, forces, and electricity are ways of transferring energy
between stores.
● Energy is dissipated in any energy transfer process because of friction, air resistance,
Key Words
electrical resistance, and heating of the surroundings by hot objects.
energy, joules, kilojoules,
● You can calculate the useful energy or the wasted energy from the energy input and energy
energy resources, fossil
output.
BIG Write
52
fuels, non-renewable,
renewable, watts, power,
kilowatts, kilowatt hours, law
of conservation of energy,
chemical energy store,
dissipated
Energy campaign
to raise awareness of energy issues
You are a local councillor who wants
in schools.
There are two parts to the campaign:
y
of food and how that links to the energ
t
ten
con
rgy
ene
the
of
ess
ren
awa
●
raising
needed for activities that people do
●
saving fossil fuels for the future.
Task
ir own
ts could use to take a snapshot of the
a Design an energy diary that studen
energy use over a day or a week.
closing
spaper that explains the link between
b Write an article for the school new
fossil fuel use.
doors or insulating buildings, cost, and
End-of-Big Idea questions
1
2
Here are some energy resources. List the
renewable energy resources.
6
You want to reduce your energy bills.
a Calculate the power of a lightbulb that
transfers 6000 J every minute. (2 marks)
b Two bulbs are equally bright. State and
explain which lightbulb you should use.
(2 marks)
c State and explain one way of reducing
the costs on your home energy bill.
(2 marks)
(6 marks)
7
A tennis ball has 0.5 J of energy when
it is 1 m above the floor.
a Name the store associated with this
energy.
(1 mark)
b A student states that there will be 0.5 J of
energy in the kinetic store just before it
hits the ground.
i Explain why the student has made that
statement.
(1 mark)
ii Explain why the student might not be
correct.
(1 mark)
c Explain why the ball moves.
(2 marks)
(5 marks)
8
Here are some data about two types
of kettle.
wind solar oil coal geothermal gas
(1 mark)
a Write the letter of the correct definition of
power below.
(1 mark)
A the energy transferred per kilogram
B the energy transferred
C the energy transferred per second
D the force over a distance
b Select all the units of power from this list:
kW J watts kilojoules kilowatts W joules kJ
3
4
5
(1 mark)
(2 marks)
a Explain, in terms of energy, why a
pendulum swings lower and lower when
you let it go.
(2 marks)
b Describe an everyday situation where
energy is dissipated by friction. (1 mark)
(3 marks)
a Name a fossil fuel that can be burned in a
power station.
(1 mark)
b Explain why it is called a ‘fossil’ fuel. (1 mark)
c Use your answer to part b to explain why
fossil fuels are non-renewable. (2 marks)
(4 marks)
A tablet charger has a power of 100 W.
a Convert 100 W to kW. There are 1000 W in
1 kW.
(1 mark)
b Calculate the cost of using the charger for
3 hours if the cost of 1 kWh is 10 p.
(2 marks)
c State and explain one way of reducing the
costs on your home energy bill. (2 marks)
(5 marks)
Energy
input
(kJ)
Useful energy
output
(kJ)
BoilFast
600
540
KettlePro
800
Kettle
Wasted
energy
(kJ)
80
a Copy and complete the table.
(2 marks)
b Calculate the efficiency of each kettle.
(4 marks)
c A student says that the BoilFast kettle
must be more efficient because it
wastes less energy. Explain why this is not
correct.
(2 marks)
(8 marks)
53