Chemistry 1 Picture Puzzler

Key Words
What is stuff made of? Everything is made up of chemicals
– the food you eat, the plastic in your phone…and you!
But what are these chemicals like inside, and why do they
behave the way they do?
Can you solve this Picture Puzzler?
In C1 you will learn about the atoms that make up
everything on Earth… and beyond. You will explore how The first letter of each of these images spells
chemical reactions make vital materials, and provide energy out a science word that you will come across
for almost everything we do. in this book.

You already know Q

Different materials have different properties. What is the name of
Picture Puzzler
Close Up
●

● The different properties of different materials make the change of state

them suitable for different uses. in which liquid water
● Many materials can exist in the solid, liquid, and gas states.
becomes ice?
Can you tell what this
● The state of a material depends on the temperature.
zoomed-in picture is?
● Changes of state are reversible.
Clue: It's a cold and
● Melting, freezing, evaporating, boiling, and condensing

are changes of state.

frosty morning.
● Changes that form new materials are not reversible.

● Changes that are not reversible include burning,

oxidation, and reactions of acid.

Making connections
BIG Questions In C1 you will learn about atoms and
molecules and what happens when chemicals react.
ide and why
• What are materials likeyins
do?
In B1 you will learn about diffusion and how particles
do they behave as the move between substances.
?
• What are atoms and elements In P2 you will learn about energy transfer and energy
materials?
• How do scientists make new
58 59
conservation.
 C1 Chapter 1: Particles and their behaviour

1.1 The particle model In a substance, every particle is the same. One gold particle is the
Key Words
same as all other gold particles. One water particle is the same as all
other water particles. In the air, all oxygen particles are identical. material, particle, mixture, substance,
But gold particles are not the same as oxygen particles. Oxygen property
Learning objectives Look around you. Can you see things made of wood, particles are not the same as water particles. Every substance has its
After this topic you will be able to: plastic, or steel? The different types of stuff that things own type of particle.
● describe how materials are
are made from are called materials. There are millions Link
of materials. B State what is meant by a substance.
made up of particles You can learn more about the
● use the particle model to
explain why different materials
What’s in a material? arrangement and movement of
Materials are made up of tiny particles. You cannot see the What gives a substance its properties? particles in C1 1.2 States of matter
have different properties. The properties of a substance describe what it looks like and how
particles. They are too small. There are about 8 400 000 000 000 000
000 000 000 particles in a glass of water. it behaves. Every substance has its own properties. The properties
of a substance depend on its particles.
A State what materials are made up of. The table shows data for gold and water.
Substance Relative mass of particle Mass of 1 cm3 of the substance (g) Summary Questions
Are all particles the same? gold 197 19
Many materials are mixtures. Wood is a mixture. So is milk, and water 18 1
1  Copy the sentences below,
choosing the correct bold words.
the air. But some materials are not mixtures. They consist of just
There are hundreds/millions of
one substance. A substance has the same properties all the way A gold particle has a greater mass than a water particle. This helps
materials. Materials are made up of
through. Substances include gold, water, and oxygen. to explain why 1 cm3 of gold weighs more than 1 cm3 of water. practicals/particles. A substance
In liquid water, particles slide over each other. In an ice cube, the has the same/different properties
particles do not move around. This explains why you can pour all the way through. In a
water from a glass but you cannot pour water from an ice cube. substance, all the particles are the
same/different. The particles of
The properties of a substance depend on three things, or factors: different substances are the same/
● what its particles are like different. The properties of a
● how its particles are arranged
substance describe its behaviour/
particles.
● how its particles move around.
(6 marks)
 old is a single substance. All of its
G
particles are the same. C List three factors that give a substance its properties. 2 Use the data to estimate
which is heavier, 10 cm3 of water
or 10 cm3 of mercury. Show how
you decided.
Vital vocab
Data: relative mass of water
Plan how to explain the meanings of the key words on this
particle = 18; relative mass of
page. Present your explanations to a partner. mercury particle = 201.
Fantastic Fact! (2 marks)
If people were the same size as gold
particles, the world’s population would 3 Using all the key words,
draw a visual summary to
fit into a ball less than a thousandth of a
summarise and organise the
millimetre across. information on this page.
60 (6 marks) 61
The bridge cables are made from steel. Steel is a mixture.
 C1 Chapter 1: Particles and their behaviour

1.2 States of matter In the solid state, particles do not move around. They vibrate
on the spot. This explains why solids cannot flow. Express particle?
T he particles of In 2010 a Chinese train became
a substance in the world’s fastest passenger train.
Learning objectives Do you like ice in cold drinks? An ice cube is made up the solid state. It reached a speed of 486 km/h
After this topic you will be able to: of water particles. Ice is water in the solid state. Now (0.135 km/s). In the air, oxygen
imagine a steaming kettle. Steam is also made up of particles travel at about 500 m/s.
● describe the properties of a
water particles. It is water in the gas state. Calculate which is faster – the train
substance in its three states
or the particles.
● use ideas about particles to Water can exist in three states, as a solid, a liquid, or a gas. These
explain the properties of a are the states of matter. The particles of water in its three states
substance in its three states. are identical. But the properties of ice, liquid water, and steam are
different. These pages explain why. The liquid state
When a substance is in the liquid state, its particles touch their Key Words
A Name the three states of matter. neighbours. This is why you cannot compress a liquid. The particles solid, liquid, gas, states of matter
move from place to place, sliding over each other. This explains
How does state affect properties? why liquids flow and why they have no fixed shape.
Most substances can exist in three states. The state of a substance T he particles of
depends on temperature. At room temperature, gold is solid. a substance in
But if you make it hot enough, gold exists as a liquid or gas.
the liquid state. Summary Questions
The table compares the properties of a substance in its three states.
1  Each sentence in the
paragraph below has one or more
Can you compress Does the
State (squash) the substance substance Shape
mistakes. Write corrected versions
in this state? flow? of the sentences.
solid no no fixed, unless you apply There are two states of matter.
a force You can compress a substance in
liquid no yes takes the shape of the the solid state because the
bottom of its container C State why you cannot compress a liquid.
particles touch each other. In the
gas yes yes takes the shape of the liquid and gas states, a substance
whole container
The gas state flows because the particles cannot
In the gas state, particles spread out. So it is easy to compress a gas. move from place to place. You
B I dentify three differences between a substance in the The particles move throughout the whole container. This explains cannot compress a gas because
the particles are spread out.
solid and liquid states. why gases flow.
(4 marks)
T he particles of
How do particles explain properties? a substance in 2 Compare the properties
the gas state. of a substance in the liquid and
The particles of a substance do not change. All water particles are gas states.
the same, in all three states. But the arrangement and movement of
(3 marks)
particles are different in each state.

The solid state

3 Use a particle model to
explain in detail why the
When a substance is in the solid state, its particles touch their properties of water are different in
neighbours. This explains why you cannot compress a solid. In the its three states.
62 Ice is water in the solid state. solid state, a substance's particles are arranged in a pattern. (6 marks QWC) 63
 C1 Chapter 1: Particles and their behaviour

1.3 Melting and freezing Using melting points Substance Melting point (°C)

Identifying substances paracetamol 169

Jackson and Marcus are at university. They have three painkillers aspirin 136
– paracetamol, aspirin, and ibuprofen. They do not know which is
Learning objectives Imagine an ice cube in your hand. What happens?
which. They use the Internet to find out their melting points. They
ibuprofen 76

After this topic you will be able to: When a substance changes from the solid to liquid state, it melts. record the data in the table shown on the right.
● use the particle model to Melting is a change of state. Freezing is the change of state The students measure the melting point of one painkiller.
explain changes of state from liquid to solid. Liquid gold freezes if cooled to 1063 °C. It is 136 ºC. They conclude that it is aspirin.
involving solids and liquids
● interpret data about A Name the two states involved in freezing. Checking purity
melting points. A single substance has a sharp melting point. Stearic acid is solid at
Explaining melting and freezing 20 °C. If you heat the acid, it stays solid up to 70 °C. Then it starts to
What happens when an ice cube melts? As ice starts to melt it takes melt. It stays at 70 °C until it has all melted. Then the liquid warms up.
in energy, so its particles vibrate faster. Particles move away from
their places in the pattern. They continue to move around. As more  pparatus used to measure
A
90
melting points.
particles leave the pattern, more ice melts. 80

Temperature (°C)
70
When a liquid starts to freeze, its particles move more slowly as they 60
transfer energy to the surroundings. The particles 50 Summary Questions
get into a pattern, and vibrate on the spot. Eventually, all the 40
liquid freezes. The mass does not change when a substance melts or 30
20
1  Copy the sentences below,
freezes. This is because no particles have been added or removed. choosing the correct bold words.
10
0 The change of state from solid to
 allium metal is solid at room
G 0 1 2 3 4 5 6 7 8 9 liquid is freezing/melting. As a
temperature. On a warm hand, B D
 escribe how particle movement changes when a Time (min)
it melts. substance melts, its particles
substance melts. The graph shows the temperature of stearic acid as it is heated. vibrate slower/faster. The particles
start moving around/upwards. The
A material that is a mixture of substances does not have a sharp
What is a melting point? substance is now in the liquid/
melting point. Chocolate melts between 30 °C and 32 °C. This solid state. The melting point of a
The temperature at which a substance melts is its melting point.
shows that it is a mixture. substance is the speed/
Substance Melting point (°C) temperature it melts at.
gallium 30 (5 marks)
Butter wouldn’t melt…
gold 1063
oxygen −218
Look at the graph. Is butter a single substance or a mixture? 2 A substance has a melting
Explain your decision. point of −7 °C. Tom says the
water 0
substance is liquid at 20 °C. Ben
L ava cools and freezes. This 40
forms rock. says it could be liquid or gas.

Temperature (°C)
Melting points give information about the states of substances at 35 Explain who is correct. Use
different temperatures. The melting points of gallium and gold are evidence to support your answer.
above 20 °C. So at 20 °C, gallium and gold are solid. You cannot 30 (3 marks)

Key Words
work out the state of oxygen from the data in the table. 25
3 Use the particle theory
20 to explain in detail the difference
melting, change of state, freezing, C L ist the substances in the table in order of increasing
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
between melting and freezing.
Time (min)
64
melting point melting point. (6 marks QWC) 65
 C1 Chapter 1: Particles and their behaviour

1.4 Boiling A student heated liquid water and plotted the graph shown on
the opposite page. At first, the temperature increased. At 100 °C, Mystery liquid
the water bubbled vigorously. It was boiling. The temperature Sarah has a liquid. It could be
remained at 100 °C. This is the boiling point of water. water, ethanol, or propanol.
Learning objectives Close your eyes. Imagine water boiling. What can you Sarah heats the liquid. It bubbles
After this topic you will be able to: hear? What can you see? When a substance is boiling it B State what is meant by the term boiling point. vigorously at 97 °C. Use data
is changing from the liquid state to the gas state. from this page to suggest what
● use the particle model to
the liquid might be.
explain boiling
● interpret data about changes
Explaining boiling Using boiling points
When water boils, bubbles of steam form all through the liquid.
of state. Identifying substances
Key Words
In the liquid, water particles touch their neighbours. Inside the
You can use data about boiling points to help identify substances.
bubbles, the water particles are spread out.
Lucy has a colourless liquid. Her teacher tells her it could be
As water boils, the steam bubbles rise to the surface of the liquid. conserve, boiling, boiling point,
Link They escape into the air. The total mass of steam and water is the
water, ethanol, or propanol. Lucy notes the boiling points of these
substances in the table below.
You can learn more about evaporation same as the mass of water at the start. Scientists say that mass is
in C2 2.5 Evaporation and distillation conserved in boiling. Substance Boiling point (°C)
water 100
A Name the substance in the bubbles in boiling water. ethanol 78 Summary Questions
propanol 97
1  Copy the sentences below,
What is a boiling point? choosing the correct bold words.
Boiling happens if the particles have enough energy. Different Lucy heats her liquid on an electric heater. She measures its When a substance boils, it
substances need different amounts of energy to boil. This means temperature every minute. At 78 °C the liquid bubbles vigorously. It changes state from liquid/gas to
liquid
that different substances boil at different temperatures. The remains at 78 °C for several minutes. Lucy concludes that the liquid liquid/gas. Bubbles form at the
gas bubble
temperature a substance boils at is its boiling point. is ethanol. top of/all the way through the
liquid. A certain substance boils at
Predicting states any/a certain temperature.
Measuring boiling point
If you know the melting point and the boiling point of a substance, (4 marks)
You can measure the boiling point of a substance like this:
you can predict its state at different temperatures. The melting and
● Pour the liquid into a beaker. boiling points of silver are shown below. 2 Use the data to predict the
● Heat the liquid, and measure the temperature every minute. state of copper at 2000 °C.
● Plot the results on a graph. melting point of silver (961 °C) boiling point of silver (2210 °C)
Data for copper:
Boiling water. melting point = 1083 °C
100 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400
boiling point = 2595 ºC
90 temperature (°C)
80 (1 mark)
Temperature (°C)

70
60 At room temperature (20 °C), silver is in the solid state. At 961 °C, 3 Design a particle model
50 the melting point, silver exists as both a solid and a liquid. Between that can explain why different
Fantastic Fact! 40 961 °C and 2210 °C silver is a liquid. At 2210 °C, the boiling point, substances boil at different
30 temperatures. Use the data on this
The boiling point of a substance depends silver exists as both a liquid and a gas. Above 2210 °C silver exists in
20 page to compare two substances
how high above the Earth’s surface you 10 the gas state. using your particle model.
are. At Mount Everest Base Camp (5364 m 0 Identify the strengths and
0 1 2 3 4 5 6 7 8 9
above sea level), water boils at 82 °C. Time (min)
C Predict the state of silver at 1000 °C. weaknesses of your model.
66 (6 marks) 67
A temperature–time graph for heating water.
 C1 Chapter 1: Particles and their behaviour

1.5 More changes of state Why is it quicker to dry your hair with a hairdryer? The hairdryer
speeds up evaporation in two ways. It provides energy to help
particles leave the liquid surface. It also moves just-evaporated
water particles away from your hair.
Learning objectives What happens to the water when you use a hairdryer to
After this topic you will be able to: dry your hair? It changes state from liquid to gas without B Identify two ways that a hairdryer speeds up evaporation.
boiling. This is called evaporation.
● describe changes of state
involving gases What is condensation?
Explaining evaporation
● use the particle model Is the inside of your bedroom window ever wet after a cold night?
In a liquid, some particles have more energy than others.
to explain evaporation, At bedtime, water particles were mixed with air particles. They were
The particles with most energy leave the liquid surface. Then they
condensation, and spread out, as a gas. During the night, water particles hit the cold
move away from the liquid. The particles spread out, forming a gas.  tage smoke is solid carbon dioxide.
S
sublimation. glass of the window. They moved closer to other water particles,
They mix with air particles. This is evaporation. It is also known as dry ice.
until they were touching. This formed liquid water. The change of
A substance can change from the liquid to the gas state by state from gas to liquid is called condensation. It can happen at
evaporating or boiling. The table below shows some differences any temperature below the boiling point.
between these two processes.

Process How particles leave the liquid Temperature Does the mass
C Identify the state formed when a substance condenses. Summary Questions
change?
evaporation Particles escape from the happens at any no 1  Write five correct sentences
liquid surface. temperature
What is sublimation? from the sentence starters and
boiling Bubbles of the substance in the happens only at the no Where does stage smoke come from? It comes from solid carbon enders below.
gas state form throughout the boiling point dioxide. Carbon dioxide is solid at temperatures below −78.5 °C. At Sentence starters
liquid. They rise to the surface this temperature and above, solid carbon dioxide changes state to In boiling…
Key Words and escape.
become a gas. It does not normally exist as a liquid. The change of In condensing…
state from solid to gas is called sublimation. In evaporating…
evaporation, condensation, sublimation
A State two differences between evaporation and boiling. Sentence enders
At first, the carbon
…particles leave from the surface
dioxide gas is very cold.
of the liquid.
How is evaporation useful? Water particles condense …substances change from the
Why do you sweat? Sweating cools you down by evaporation. around carbon dioxide liquid to the gas state.
Sweat comes out of pores in your skin. Water from the sweat particles. Tiny drops of …particles leave from all parts of
evaporates. The water particles need energy to move away as a gas. liquid water form. It is this the liquid.
They take this energy from your skin. This cools you down. liquid water that makes …substances change from the gas
Evaluating evaporation stage smoke. to the liquid state.
Eva is investigating evaporation. (5 marks)
She puts a small, damp tissue in
a cold place. She puts a big, wet
2 Describe the changes in
behaviour of the particles when a
towel above a heater. The tissue substance condenses.
dries first. Eva concludes that cold  olid grey iodine sublimes
S (2 marks)
conditions speed up evaporation. to form a purple gas.
Evaluate Eva’s investigation: How 3 Compare the processes
could she improve it? Does the  weat helps
S of evaporation, boiling, and
to cool you D N
 ame the change of state that occurs when a substance condensation.
evidence support the conclusion? down by
68 in the solid state changes into a gas. (6 marks QWC) 69
evaporation.
 C1 Chapter 1: Particles and their behaviour

1.6 Diffusion Particle size

A teacher sets up the apparatus below to demonstrate diffusion.

Solid ammonium
chloride forms here.
Learning objectives Do you wear perfume or deodorant? How does the smell
After this topic you will be able to: reach your nose?
● use the particle model to
Perfume particles evaporate from your skin. The particles move
explain diffusion
around randomly. They mix with the air. As the perfume particles
● describe evidence for diffusion. cotton wool soaked cotton wool soaked Particles of potassium manganate(VII)
spread out, some enter your nose. Your nose detects the smell. The diffuse through the water.
in concentrated in concentrated
random moving and mixing of particles is called diffusion. hydrochloric acid ammonia solution

Summary Questions
New style to Hydrogen chloride particles evaporate from the piece of
come at next cotton wool at the left side of the test tube. Ammonia particles 1  Copy and complete the
proof sentences using the words below.
evaporate from the piece of cotton wool at the right. The
particles randomly air
particles diffuse along the tube. The two types of particle meet,
diffusion energy faster
and form a ring of white solid. The solid is closer to the hydrogen
When food cooks, you can smell it
chloride end. This shows that the hydrogen chloride particles
because some leave the
diffuse more slowly. Hydrogen chloride particles are bigger and food. The particles move
heavier than ammonia particles. Big, heavy particles diffuse more
Why do substances diffuse? slowly than small, light ones.
and mix with the . This is
called . Particles diffuse
C
 oloured ink particles diffuse through Particles diffuse because they have energy. Perfume particles
because they have . The
water. There is no need to stir. move randomly in the air, even if the air seems completely still. Ink State higher the temperature, the
particles spread through water by themselves. You do not need Diffusion happens quickly in gases. This is because the particles the diffusion.
to shake or stir. are far apart. A particle in a gas travels a long way before hitting (6 marks)
another particle.
Fantastic Fact! 2 Describe three pieces of
A State what is meant by diffusion. In the liquid state, particles are closer than in the gas state. This is
At room temperature, particles in liquid evidence for diffusion.
why diffusion is slower in liquids.
water move at an average speed of (3 marks)
1600 km/h (444 m/s). What factors affect diffusion speed? Diffusion does not happen in solids. The particles cannot move
3 The air contains particles of
Diffusion does not always happen at the same speed. Three factors from place to place. argon, nitrogen, and other
affect the speed of diffusion: substances. Use the data below to
● temperature predict which type of particle
Fair’s fair diffuses faster. Give a reason for
Key Words ● particle size

● the state of the diffusing substance.

Raj investigates how temperature affects diffusion speed. He your choice.
diffusion puts purple crystals into five test tubes. He adds water of a Relative masses of particles:
Temperature different temperature to each test tube. He watches the purple nitrogen = 28 and argon = 40
At higher temperatures, particles have more energy. They move colour spread through the water. Identify the variables Raj (2 marks)
more quickly. Perfume particles leaving warm skin travel faster than should change, measure, and control to make it a fair test.
4 Explain in detail the
Link perfume particles leaving a cold bottle.
different diffusion speeds through
substances in the solid, liquid, and
You can learn more about diffusion in B E
 xplain why particles diffuse more quickly at higher gas states.
70
B1 1.4 Movement of substances temperatures. (6 marks QWC) 71
 C1 Chapter 1: Particles and their behaviour

1.7 Gas pressure How does temperature affect pressure?

Key Words
Hotter and hotter
collide, gas pressure
Balloons sometimes burst on hot days. Why does this happen?
Learning objectives Why do balloons get bigger as you blow them up? When
After this topic you will be able to: you blow up a balloon, you are filling it with air particles.
The more air particles you add, the bigger the balloon.
● use the particle model to New style to
explain gas pressure come at next
● describe the factors that proof
affect gas pressure.

Fantastic Fact!
Racing-car tyres reach 100 ºC. Before a As the air in a balloon gets warmer, its particles gain energy.
The particles move faster. They collide with the rubber more often.
race, technicians pump tyres to a lower
pressure than they need in the race. The The pressure inside the balloon increases. Summary Questions
air pressure in the tyre increases as it The higher the temperature, the higher the air pressure. At first the 1  Copy the true sentences below.
heats up. rubber stretches. As the temperature gets even higher, the rubber Write corrected versions of the
The more particles you blow into a balloon, the bigger the balloon. cannot withstand the greater pressure. Eventually, it cannot stretch false sentences.
any further and the balloon bursts. Gas particles collide with the walls
Inside the balloon, the air particles move quickly from place to of their container.
place. They bump into, or collide with, each other. They also collide Cooling down
Imagine a plastic bottle of air in a freezer. The air cools down and its Colliding gas particles exert
with the rubber the balloon is made from. The collisions exert a pressure on the inside of the
force on the rubber. The force per unit area (every square metre) is particles lose energy. The particles move more slowly. They collide
06.05.02 & 03 Science Works Bk1
the gas pressure. with the plastic less often. The pressure in the bottle decreases. The
container.
The more particles in a container,
Barking
Gas Dogexert
particles always Artpressure on the walls of their container, particles outside exert a higher pressure than the particles inside. the lower the pressure.
The bottle collapses.
whatever the container is made from. The higher the temperature, the
lower the pressure.
T he air pressure in racing-car tyres (4 marks)
increases during a race. A State what is meant by gas pressure.
2 Jack was camping. He put a
can of baked beans on his camp
How does the number of particles affect pressure? fire, without opening the lid. The
Rubber is stretchy. So when you blow more particles into a balloon, I n the freezer, can exploded. Use ideas about
Particle performance the balloon expands. the air pressure
particles to explain why.
Read the Fantastic Fact before inside the bottle
But some containers cannot expand. Adding more particles causes decreases. (3 marks)
you do this task.
more frequent collisions with the walls. The pressure inside the
Racing-car tyres are pumped full of 3 Plan a talk that you
container increases. Now imagine taking the bottle out of the freezer. The air inside the could give to another class to
air. Write a script for particles in a
bottle warms up. Soon, the air particles inside and outside the bottle explain what happens to an
racing-car tyre. What do they say 06.05.06 Science Works Bk1
exert the same
Barking Dogpressure.
Art The bottle returns to its normal shape. inflated balloon when you put it in
as the car goes faster and the air B E
 xplain why adding more air increases the pressure a warm room and when you put it
gets hotter? Then perform inside a container. in a fridge.
your script. C Explain why a bottle collapses in the freezer. (6 marks) 73
72
 C1 Chapter 1 Summary End-of-chapter questions

1  The diagram shows some particles in solid e Name one substance in the table that is in
gold. Draw another diagram to show particles the liquid state at 100 ºC.
of gold in the gas state. (1 mark)

Key Points
(2 marks) (10 marks)

● Materials are made up of tiny particles. 4 Read the statements about particles
● A substance is a material that has the same properties all the way through. in a substance in the solid state.
● The properties of a substance describe what it looks like and how it behaves. A The particles touch other particles.
● The properties of a substance depend on what its particles are like, and B The particles are in a pattern.
how they are arranged. C  The particles do not move around from
● There are three states of matter – solid, liquid, and gas. For a certain
place to place.
substance, the particles never change. But in different states, the particles move
D The particles vibrate.
differently, and have different arrangements.
● In the solid state, you cannot compress a substance, or make it flow. a W rite down the letter of the statement that
●
2 Describe the arrangement and movement best explains why you cannot pour a solid.
In the liquid state, you cannot compress a substance, but you can make it flow.
●
of particles in the liquid state. (1 mark)
In the gas state, you can compress a substance, and make it flow.
●
(2 marks) b Choose one of the other statements and
The change of state from solid to liquid is melting. A substance melts at its melting
point. Pure substances have sharp melting points. explain why it does not explain why you
● A substance changes from the liquid to the gas state by evaporating or boiling. 3  The table shows the melting points and cannot pour a solid.
A substance boils at its boiling point. boiling points of six substances. (1 mark)
● The change of state from gas to liquid is condensing. Substance Melting point (°C) Boiling point (°C) (2 marks)
● The change of state from liquid to solid is freezing. bromine −7 59
● Some substances change directly from the solid state to the gas state. This is subliming.
krypton −157 −152
5  Olivia says that gas pressure is the
● Diffusion is the random moving and mixing of particles.
mercury −39 357
result of particles colliding with each other.
● Gas particles collide with the walls of their container. The collisions cause gas pressure.
neon −249 −246
Is Olivia correct? Explain your answer.
platinum 1769 4530 (2 marks)
silver 961 2210

Maths Challenge
6  Write a few paragraphs to compare
a Write down the name of the substance with the processes of boiling and evaporating.
the highest boiling point. (6 marks QWC)
Up in the air
table shows the percentages Key Words (1 mark)
The air is a mixture of substances. The b Write down the names of the substances in
material, particle, mixture,
of the substances in the air. order of increasing melting point, starting
substance, property, solid,
Substance Percentage of substance in dry air liquid, gas, states of matter, with the lowest.
78.08 melting, change of state, (5 marks)
nitrogen
20.95 freezing, melting point, c Name one substance in the table that is in
oxygen
0.93 boiling, boiling point, the gas state at 20 ºC.
argon
0.04 conserve, evaporation, (1 mark)
others, including carbon
dioxide condensation, sublimation, d Name two substances in the table that are
diffusion, collide, gas pressure in the liquid state at 20 ºC
Task (2 marks)
a pie chart to represent the
74 Draw a bar chart, a scatter graph, and 75
chart is best, and explain why.
data in the table. Decide which type of