Brown's Chemistry AQA GCSE Science-CHEMISTRY 3 Revision Notes
CHEMISTRY UNIT 3 Chemistry 3
for GCSE Triple Award Science or GCSE Chemistry
REVISION NOTES GUIDE SUMMARY: What do you need to know
for the examinations? What do you need to able to do in the exams? In AQA GCSE Science
A examinations HT means for higher tier students only.
Sorry, but I don't have much time to answer questions, but if you see any
apparent errors or wish to comment, please
email me. All my notes, learning
objectives, comments for exam revision are based on the official AQA GCSE Science A Key Stage 4
Throughout this unit you will be
expected to write word equations for reactions specified.
Higher tier (HT)
candidates will also be expected to write and balance symbol
equations for reactions specified throughout the unit.
AQA GCSE Science CHEMISTRY
Unit C3.2 Water
The water we drink is not pure water because it contains dissolved substances.
It should be safe to drink water
that has been treated.
the dissolved substances are beneficial to our health but some cause hard water.
You should be able to use your skills, knowledge
and understanding to:
evaluate the use of commercial water softeners,
consider and evaluate the environmental, social and
economic aspects of water quality and hardness,
consider the advantages and disadvantages of
adding chlorine and fluoride to drinking water,
Summary of syllabus-specification
statements expressed as learning objectives for
AQA GCSE Science CHEMISTRY Unit
C3.2.1 Hard and soft water
a) Know that soft water readily forms lather with soap.
Know that hard water
reacts with soap to form scum and so more soap is
needed to form lather.
Know that soapless detergents do not
You should know how to measure the hardness of
water by titration with soap solution and be able to do it.
b) Know that hard water contains dissolved compounds, usually of
calcium or magnesium.
c) Know there are two types of hard water.
water remains hard when it is boiled.
water is softened by boiling.
You should be able to distinguish between
temporary hard water and permanent hard water.
d) HT only: Know that temporary hard water contains
hydrogencarbonate ions (HCO3-) that
decompose on heating to produce carbonate
ions which react with calcium and magnesium
ions to form precipitates.
e) Appreciate that using hard water can increase costs because more
soap is needed.
f) Know that hard water has some benefits because calcium
compounds are good for the development and
maintenance of bones and teeth and also help
to reduce heart disease.
g) Know and understand that hard water can be made soft by removing the dissolved
calcium and magnesium ions.
Revision Notes Hard
and soft water - causes and treatment
AQA GCSE Science CHEMISTRY Unit
C3.2.2 Purifying water
a) Appreciate that water of the correct quality is essential for life.
Appreciate that for
humans, drinking water should have sufficiently low
levels of dissolved salts and microbes.
Know that water of the correct quality is produced by:
choosing an appropriate source
passing the water through filter beds to remove
sterilising with chlorine.
b) Know that water filters containing carbon, silver and ion
exchange resins can remove some dissolved
substances from tap water to improve the taste
Detailed knowledge of specific water filters is not
Examination questions may give information about
water filters so that comparisons can be made.
You should understand the principles of how
ion exchange resins work but do not need detailed
knowledge of the structure or chemical nature of
c) Know and understand that chlorine may be added to drinking water to reduce
microbes and fluoride may be added to improve
d) Pure water can be produced by distillation.
cycle, treatment including filtration and chlorination, pollution
AQA GCSE Separate Science CHEMISTRY
for triple award
When revising, these pages
provide you with a summary of what you need to know and be able to do.
BUT remember, your primary
source of revision are your class notes, investigations and AQA GCSE
Revision notes and quizzes to
help you revise
Triple Award Separate Science AQA
Chemistry Unit 3 C3 Unit Index
GCSE Science-Chemistry courses
AQA GCSE Science A CHEMISTRY *
EDEXCEL GCSE Science
OCR GCSE 21st Century
Science A CHEMISTRY * OCR GCSE Gateway
Science B CHEMISTRY
Science-CHEMISTRY * Northern
Ireland CCEA GCSE Science-CHEMISTRY
AQA GCSE Sciences - Revision
Notes - Learning Objectives - PREVIOUS PAGE *
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