I N T E R N AT I O N A L

Written by experienced practitioners, these resources provide comprehensive preparation and support for Edexcel International GCSE.

Written in a clear, engaging style that all students will find easy to understand.

Activities and exercises for self-study, as well as exam-style questions and summaries to aid revision.

Engaging digital resources for additional learning and revision support.

Edexcel-endorsed resources for the latest specifications

Student Books Free ActiveBook CDs (available for most subjects)

contain a digital version of the Student Book, interactive activities and questions, revision material, glossaries and more.

Enhanced eBook versions of selected revision guides include quizzes, worksheets and answers.

Chapter summaries and key points for all specification topics.

Example questions and answers for essential exam practice.

Revision tips, techniques and advice, including a glossary of key terms.

Chapter 19: Density and Pressure

One way of characterising materials is by their density. This chapter looks at

density and at how materials can affect things around them by exerting pressure.

Section E: Solids, Liquids and Gases

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Figure 19.1 Some effects of density and pressure.

The properties of a material affect how it behaves, and how it affects other materials

around it. The balloon can fly because the gas inside it has a very low density. The skis

spread the weight of the skiers over the snow so they do not sink into it. The

submersible is designed to explore the sea bed – it has a very strong hull to withstand

the high pressure from water deep in the oceans.

Density

Solids, liquid and gases have different properties and characteristics. One such

characteristic is density. Solids are often very dense, that is, they have a high mass

for a certain volume. Liquids are often less dense than solids, and gases have very

low densities.

The density (ρ) of a material can be calculated if you know the mass (m) of a

certain volume (V ) of the material, using this equation.

density, ρ = mass, m

volume, V

ρ = mV

The units for density depend on the units used for mass and volume. If mass is

measured in kilograms and volume in cubic metres, the units for density are

kilograms per cubic metre (kg/m3). Density can also be measured in grams per

cubic centimetre (g/cm3).

ρ is the Greek letter rho and is the usual

symbol for density.

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The density of a substance can be determined by measuring the mass and volume

of a sample of the material, and then calculating the density.

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Worked example

Example 1

A piece of iron has a mass of 390 kg and a volume of 0.05 m3. What is its density?

density, ρ = mass, m

volume, V

ρ = mV

= 390 kg0.05 m3

= 7800 kg/m3

Figure 19.3 a) The volume of a regular solid can be calculated by multiplying its length (l), width (w) and

height (h). b) The volume of an irregular object can be determined using a displacement can and a

measuring cylinder.

If an examination question asks you to write

out the formula for calculating density, mass

or volume, always give the actual equation

(such as ρ = m/V). You may not be awarded

the mark if you just draw the triangle.

Check the units when you are working out

density – don’t mix up g and m3, for example.

Also check which units the question asks for

in your final answer.

1 kg = 1000 g

To convert kg to g, divide by 1000.

1m3 = 1 000 000cm3

To convert cm3 to m3, divide by 1 000 000

(or 106).

Alternatively, work out the density in g/cm3,

then multiply your answer by 1000.

Worked example

Example 2

The mass of 50 cm3 of a liquid and a measuring cylinder is 146 g. The mass of the

empty measuring cylinder is 100 g. What is the density of the liquid in kg/m3?

Mass of 50 cm3 liquid = 146 g − 100 g

= 46 g

= 0.046 kg

50 cm3 = 0.000 05 m3

ρ =

mV

=

0.046 kg

0.000 05 m3 or =

46 g50 cm3

= 0.92 g/cm3

= 920 kg/m3 = 920 kg/m3

Figure 19.2 The equation for density can be

rearranged using the triangle method.

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Keep your reader interested◊ Compare the two pieces of writing below. Which do you think is most likely to engage the reader

and why?

◊ Now look at the examiner’s feedback below. See if you can match each one to either extract

A or extract B.

Language techniquesThis is a selection of some of the language techniques that an examiner might want to see in your work –

these help you to enrich your writing.Alliteration Repetition of the fi rst-syllable sound of several

words near each other in a phrase. ‘… the silent stillness…’Assonance Repetition of a vowel sound in several words

near each other in a phrase. ‘…glossy clot…’Hyperbole Exaggeration for effect.

‘… it is the most frightening thing you will ever see…’

Metaphor A comparison of two objects that implies that one is the same as the other. ‘…a blanket of fog…’

Onomatopoeia A word that resembles the sound that it describes.

‘trickle’ or ‘snap’Personifi cation Application of human characteristics to an inanimate object. ‘…the car roared and snarled…’

SimileA comparison of two things that suggests that one is like another. ‘… as fast as wild horses…’

◊ How many of these can you spot in extract B?Provide an effective endingThe two most important sentences you will write are the fi rst and the last

as they set and seal the tone. Your ending should:• Create an impact on the reader.• Answer the question, or in some way ‘sum up’ the story you are telling.

• Show your fl air in writing.Again, let’s consider those three vital elements:• Purpose: a good fi nal paragraph should complete the narrative while

still being true to the style.• Audience: the ending of your story should make your work stand out

in the mind of the reader and provide a satisfying fi nish.• Technique: this is your last chance to make an impact on the reader so

try to use the same standard of writing you have employed throughout

your piece.

Jenny and Mike were walking through the nature reserve when all of a sudden they heard a rustling sound coming from behind them. They looked round but didn’t see anything so they just kept walking. It was a sunny day but a bit windy. They thought they heard the noise again and both got a spine-tingling feeling as they walked further on.

We held hands as we walked on that beautiful, blue-sky day, the wind gently tugging at my hair and playing through the leaves of the trees. Mike

looked over and smiled at me, a look I’ll never forget now. It was then that we � rst heard the noise. It was as if there was a creature in the long grass, moving stealthily towards us. I told myself I was

being silly, and walked on.

A

B

The story seems a bit obvious, perhaps something the student has seen on TV. It is not very interesting and there is little sense of the two characters who are introduced. The order of the story seems a bit odd.

Interesting word choices and phrasing as well as some sophisticated language techniques such as alliteration and personi� cation help to enrich the text. Sentences are used to build the tension.

The story is starting to develop well as the reader learns about the relationship between the characters. The reader gets a sense of foreboding – that something terrible is about to happen.

Word choices and phrasing are somewhat clichéd and there is very little description in the story. Again this feels very inspired by TV. Sentences tend to be long and rambling without any effect – the focus is too much on narrative and not enough on style.

Some students write a list of the techniques they feel confi dent of in the corner of their exam paper when they are in the planning stage and then check that they have included at least one of each when they read their work over.

TOP TIP ✓✓

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Chapter introductions set the scene and focus learning.

Key facts highlighted throughout each chapter apply learning to real-life situations.

‘Did you know?’ boxes provide additional information and useful discussion points to extend learning.

eBook titles available

Revision GuidesGo Digital

ScienceBiology Student Book 978 0 435966 88 1**Chemistry Student Book 978 0 435966 89 8**Physics Student Book 978 0 435966 90 4**Human Biology Student Book 978 0 435044 13 8Science Double Award Student Guide 978 0 435046 77 4MathematicsMathematics A Student Book 1 978 0 435966 91 1**Mathematics A Student Book 2 978 0 435966 92 8**Mathematics A Practice Book 1 978 0 435044 16 9Mathematics A Practice Book 2 978 0 435044 15 2Mathematics B Student Book 978 0 435044 10 7Further Pure Mathematics Student Book 978 0 435044 14 5BusinessBusiness Studies Student Book 978 0 435046 74 3**Accounting Student Book 978 0 435991 29 6**Economics Student Book 978 0 435991 28 9**ICT Student Book 978 0 435044 11 4

Language and HumanitiesEnglish A & B Student Book 978 0 435991 26 5**English Literature Student Book 978 0 435046 75 0**English as a Second Language Student Book 2nd Edition 978 0 435158 95 8***English as a Second Language Teacher Book 2nd Edition 978 0 435158 96 5***Geography Student Book 978 0 435016 95 1**History Student Book 2nd edition 978 0 435141 90 5Arabic First Language Student Book 978 1 408275 68 9

Revision GuidesBiology Revision Guide 978 0 435046 76 7*Chemistry Revision Guide 978 0 435046 72 9*Physics Revision Guide 978 0 435046 73 6*Economics Revision Guide 978 1 446905 73 9***English A Revision Guide 978 1 446905 75 3***Geography Revision Guide 978 1 446905 77 7***ICT Revision Guide 978 1 446905 79 1***

Edexcel-endorsed resources for the latest International GCSE specifications

Go online for sample chapters and more resources for International GCSE:

www.pearsonglobalschools.com/IntGCSE

*Student Answer CD included **ActiveBook CD included ***Enhanced eBook included