KS3 CHEMISTRY:
Pure and Impure Substances
This is one of a series of documents designed to support science departments to integrate engaging and purposeful practical and investigative science activities within their current schemes of learning.
They highlight opportunities throughout the KS3 National Curriculum and identify possible purposes for each activity relating to the ‘Getting Practical’ project.
About this section of the curriculum
Pupils should be taught about:
• the concept of a pure substance
• mixtures, including dissolving
• diffusion in terms of the particle model
• simple techniques for separating mixtures: filtration, evaporation, distillation and chromatography
• the identification of pure substances.
PAGE 1
Produced in partnership with the Association for Science Education
www.timstar.co.uk
KS3 CHEMISTRY:
Pure and Impure Substances
This is one of a series of documents designed to support science departments to integrate engaging and purposeful practical and investigative science activities within their current schemes of learning.
They highlight opportunities throughout the KS3 National Curriculum and identify possible purposes for each activity relating to the ‘Getting Practical’ project.
Learning demand
The key concepts in this section of the curriculum are the differences between elements, mixtures and compounds; what a
‘pure’ material is; how mixtures can be separated.
Compounds and mixtures are a fairly concrete concept but explaining these in terms of the particle theory is very complex
making this Unit intermediate in terms of learning demand. The more opportunities that pupils have to undertake practical
activities and explain the processes in terms of the particle theory, the more familiar it will become to pupils. For further
information and support, see the Secondary National Strategy materials: ‘Strengthening teaching and learning of particles’.
http://www.nationalstemcentre.org.uk/elibrary/resource/5318/strengthening-teaching-and-learning-of-particles-key-stagethree-national-strategy-training-materials
PAGE 2
Produced in partnership with the Association for Science Education
www.timstar.co.uk
KS3 CHEMISTRY:
Pure and Impure Substances
This is one of a series of documents designed to support science departments to integrate engaging and purposeful practical and investigative science activities within their current schemes of learning.
They highlight opportunities throughout the KS3 National Curriculum and identify possible purposes for each activity relating to the ‘Getting Practical’ project.
Where this section of the curriculum fits in
This section of work covers some aspects of the several QCA topics. The most significant links are:
7G Particle model of solids, liquids and gases
7H Solutions
8E Atoms and elements
PAGE 3
Produced in partnership with the Association for Science Education
www.timstar.co.uk
KS3 CHEMISTRY:
Pure and Impure Substances
This is one of a series of documents designed to support science departments to integrate engaging and purposeful practical and investigative science activities within their current schemes of learning.
They highlight opportunities throughout the KS3 National Curriculum and identify possible purposes for each activity relating to the ‘Getting Practical’ project.
Expectations
Within this section of the curriculum
in terms of working scientifically
all pupils will: make observations and measurements of mass and temperature and, with help, present these as line
graphs
most pupils will: make observations and measurements of mass and temperature; present results as line graphs and
interpret these using scientific knowledge and understanding
some pupils will have progressed further and will: explain how scales they chose for graphs enabled them to
present results effectively; make suggestions of additional work to test conclusions of their investigations
in terms of Chemistry: Pure and impure substances
all pupils will: name some soluble and insoluble solids; describe how pure water can be obtained from sea water and
how different colours can be separated from some inks; describe how some mixtures could be separated and recognise
changes of state in elements and compounds
most pupils will: classify some solids as soluble or insoluble and explain the meaning of the term ‘saturated solution’;
begin to use the particle model to explain what happens when a solid dissolves in water, explaining why mass is conserved;
name and describe some common mixtures and use knowledge about separation techniques to suggest how they might be
separated; identify melting and boiling points as the fixed temperatures at which elements and compounds change state,
and use the particle model to explain changes of state
some pupils will have progressed further and will: explain their criteria for classifying materials as elements,
compounds or mixtures; describe how mixtures do not change state at fixed temperatures; use the particle model to explain
a range of phenomena; make links between this section of the curriculum and others
PAGE 4
Produced in partnership with the Association for Science Education
www.timstar.co.uk
KS3 CHEMISTRY:
Pure and Impure Substances
This is one of a series of documents designed to support science departments to integrate engaging and purposeful practical and investigative science activities within their current schemes of learning.
They highlight opportunities throughout the KS3 National Curriculum and identify possible purposes for each activity relating to the ‘Getting Practical’ project.
Health and safety
Risk assessments are required for any hazardous activity. Ensure that guidance is followed by referring to the latest editions
of Safeguards in the School Laboratory, Topics in Safety and current CLEAPSS documentation.
In this section of the curriculum pupils:
• carry out a number of chemical reactions
• plan and carry out an investigation of temperature changes
• use highly flammable and harmful substances
PAGE 5
Produced in partnership with the Association for Science Education
www.timstar.co.uk
KS3 CHEMISTRY:
Pure and Impure Substances
This is one of a series of documents designed to support science departments to integrate engaging and purposeful practical and investigative science activities within their current schemes of learning.
They highlight opportunities throughout the KS3 National Curriculum and identify possible purposes for each activity relating to the ‘Getting Practical’ project.
Language for learning
Through the activities in this unit pupils will be able to understand, use and spell correctly:
• words with precise scientific meaning, e.g. element, compound, mixture, atom, composition, pure, solution, solute,
solvent, soluble, insoluble, saturated solution
• names of compounds, e.g. sodium carbonate, calcium chloride, hydrochloric acid
• words describing processes e.g. dissolving, filtering, evaporating, distilling
• words and phrases relating to explanations using the particle model, eg particle, attracted, mixing, mingling
• words with similar spelling but different meanings, and use them in a consistently correct way, e.g. affect, effect
Through the activities pupils could:
• organise facts/ideas/information in an appropriate sequence
• group sentences into paragraphs which have a clear focus
• link ideas and paragraphs into continuous text that is organised and coherent
PAGE 6
Produced in partnership with the Association for Science Education
www.timstar.co.uk
KS3 CHEMISTRY:
Pure and Impure Substances
This is one of a series of documents designed to support science departments to integrate engaging and purposeful practical and investigative science activities within their current schemes of learning.
They highlight opportunities throughout the KS3 National Curriculum and identify possible purposes for each activity relating to the ‘Getting Practical’ project.
Resources
Resources include:
Equipment Links:
• simulation software, three-dimensional models to
illustrate particle arrangement and movement in solids,
liquids and gases
IGNEOUS ROCK SAMPLE PACKS
METAMORPHIC ROCK SAMPLES
PACK
CLASS ROCK SET
• samples of rocks that are mixtures
• samples of everyday materials that are mixtures, e.g. milk powder, cola
• sources of information, e.g. video clips, about the composition of air and the uses
of its constituents, e.g. British Oxygen leaflets
• database software and other data sources showing melting points and boiling
points of elements and compounds
VISION DATALOGGER
TEMPERATURE SENSOR
• temperature sensor and software
• prepared data about:
– the solubility of different solids in water
– the solubility of solids in different solvents
– the variation of solubility of solids in water with temperature (as tables and graphs)
• chromatograms for interpretation
• software simulation of particles in mixtures
• secondary sources showing uses of chromatography, e.g. caffeine determination
in drinks, identifying traces of photoallergens (causing irritation) in germicides and
soaps, identification of sugars in urine, identification of traces of drugs in horses
PAGE 7
Produced in partnership with the Association for Science Education
www.timstar.co.uk
KS3 CHEMISTRY:
Pure and Impure Substances
This is one of a series of documents designed to support science departments to integrate engaging and purposeful practical and investigative science activities within their current schemes of learning.
They highlight opportunities throughout the KS3 National Curriculum and identify possible purposes for each activity relating to the ‘Getting Practical’ project.
Independent learning
Pupils could:
• visit libraries or museums to find out more about the mixtures of rock particles in different sedimentary rocks
•u
se the internet to research how the composition of the air has changed over time and the impact that this has had on life
on Earth; where distilled water is used and about other uses of distillation
• look at labels of household liquids to find out whether they are pure liquids or mixtures
PAGE 8
Produced in partnership with the Association for Science Education
www.timstar.co.uk
KS3 CHEMISTRY:
Pure and Impure Substances
This is one of a series of documents designed to support science departments to integrate engaging and purposeful practical and investigative science activities within their current schemes of learning.
They highlight opportunities throughout the KS3 National Curriculum and identify possible purposes for each activity relating to the ‘Getting Practical’ project.
Getting Practical
The purpose of the practical work identified in this document relate to Getting Practical: Improving Practical Work in Science
http://www.gettingpractical.org.uk/
There is a detailed paper which supports the Getting Practical project written by Robin Millar entitled Analysing practical
activities to assess and improve effectiveness: The Practical Activity Analysis Inventory (PAAI)
A copy of this paper can be found at:
http://www.york.ac.uk/media/educationalstudies/documents/research/Analysing%20practical%20activities.pdf
Getting Practical learning objectives:
A: By doing this activity, pupils should develop their understanding of the natural world
A1: Pupils can recall an observable feature of an object, or material, or event
A2: Pupils can recall a ‘pattern’ in observations (e.g. a similarity, difference, trend, relationship)
A3: Pupils can demonstrate understanding of a scientific idea, or concept, or explanation, or model, or theory
B: By doing this activity, pupils should learn how to use a piece of laboratory equipment or follow a standard practical
procedure
B1: Pupils can use a piece of equipment, or follow a practical procedure, that they have not previously met
B2: Pupils are better at using a piece of equipment, or following a practical procedure, that they have previously met
C: By doing this activity, pupils should develop their understanding of the scientific approach to enquiry
C1: Pupils have a better general understanding of scientific enquiry
C2: Pupils have a better understanding of some specific aspects of scientific enquiry
PAGE 9
Produced in partnership with the Association for Science Education
www.timstar.co.uk
KS3 CHEMISTRY:
Pure and Impure Substances
This is one of a series of documents designed to support science departments to integrate engaging and purposeful practical and investigative science activities within their current schemes of learning.
They highlight opportunities throughout the KS3 National Curriculum and identify possible purposes for each activity relating to the ‘Getting Practical’ project.
Possible practical activities
Possible practical activities
Purpose
Equipment Links
Iron filings fine
IR3206
Sulphur fine powder
SU6040
Sand, fine white
SA5278
Sodium chloride
SO5528
Investigating mixtures and their separation e.g. iron/sulfur; sand and salt; sand, salt, sawdust and iron
filings; chalk in water; seawater; air; rocks; ink.
The purpose of this activity is to explore methods of separation based on simple physical properties such
as magnetic/non-magnetic, soluble/insoluble, solid/liquid, evaporates/does not evaporate.
Emphasise that mixtures can vary in composition and establish what constitutes a pure substance
(this could be a pure element or pure compound).
Common misconception: the word ‘pure’ has a different meaning to children than the scientific meaning.
They often associate ‘pure’ with meaning no additives e.g. ‘pure’ orange juice
A1
B1
A3
C2
Calcium carbonate
precipitated
CA1846
Ink, brown
CH90652
Ink, royal blue
CH90654
Ink, green
http://www.nuffieldfoundation.org/practical-chemistry/separating-sand-and-salt
CH90656
Ink, blue/black
CH90660
Chromatography sheets
CH04020
Bar magnet Alnico
MA10130
Investigating the factors that affect the solubility of some substances e.g. sugar and copper sulfate
The purpose of this activity is to show pupils:
A3
B2
C2
• that solubility may be affected by temperature, volume of solvent, stirring, particle size etc.
• there is a saturation point
• to practise key practical skills such as identifying and controlling variables, constructing tables,
drawing graphs, pattern seeking and drawing conclusionss
Sucrose
Separating coloured compounds using chromatography.
This activity allows pupils to undertake separation of inks or dyes by chromatography and to explain the
process in terms of the particle theory. More able pupils could calculate Rf values.
http://www.nuffieldfoundation.org/practical-chemistry/chromatography-sweets
A3
B2
C1
SU6001
Copper sulphate
5 water
CO2260
Thermometer -10-110
TH15425
Researching the constituents of air, how these can be separated and why we separate them.
The purpose of this activity is for pupils to name the main gases present in air and
• give approximate proportions of these identify which of these are elements and
C1
• which are compounds explain how air can be separated into its components
• describe some uses of the components of air
PAGE 10
Produced in partnership with the Association for Science Education
www.timstar.co.uk
KS3 CHEMISTRY:
Pure and Impure Substances
This is one of a series of documents designed to support science departments to integrate engaging and purposeful practical and investigative science activities within their current schemes of learning.
They highlight opportunities throughout the KS3 National Curriculum and identify possible purposes for each activity relating to the ‘Getting Practical’ project.
Possible practical activities
Purpose
Equipment Links
Aluminium potassium
sulphate 12 water
AL1162
Purifying an impure solid (alum)
The purpose of this practical is for pupils to obtain a pure solid by dissolving, filtration, evaporation and
crystallisation.
http://www.nuffieldfoundation.org/practical-chemistry/purification-impure-solid
A3
B2
C2
Evaporating basin
BA01626
Watch glass
WA17510
Filter paper
FI07244
Recovering pure water from a copper sulfate solution
This activity allows pupils to see that the blue solution boils to give the colourless solvent (water). The
boiling point of the solvent is measured and should be steady and close to 100°C (depending on the
accuracy of the thermometer, and the pressure); it also allows them to use new apparatus.
A3
B1
C1
http://www.nuffieldfoundation.org/practical-chemistry/recovering-pure-water-solution-using-watercondenser
Separating two immiscible liquids
This activity shows pupils that some liquids do not dissolve in each other and can be separated using a
separating funnel; it also allows them to use a new piece of apparatus
http://www.bbc.co.uk/schools/gcsebitesize/science/add_edexcel/covalent_compounds/
seperationrev1.shtml
B1
C1
14/23 Single joint set
(BU’M set)
JG93080
Copper sulphate
5 water
CO2260
Separating funnel
250ml
FU08470
Vegetable oil
OI4408
Magnetic stirrer
ST150510
Stirring bar 25mm
ST14425
Extracting iron from breakfast cereals
This activity is to show pupils that iron is in breakfast cereals and that it can be easily separated using a
strong magnet
B1
C1
http://www.nuffieldfoundation.org/practical-chemistry/extracting-iron-breakfast-cereal
Stirring bar retriever
ST14470
Mortar and pestle
100mm
MO11340
Neodymium magnet
10x8mm
MA30500
Researching boiling points and melting points of some elements.
The purpose of this activity is for pupils to recognise that that changes of state of pure elements and
compounds occur at a fixed temperature and that the temperature is a characteristic of the material that
is changing state; the melting point or boiling point of a mixture varies with composition
Observing the properties of liquid nitrogen
The purpose of this activity is challenge pupils’ thinking about elements that are gases and to show that
gases can be cooled enough to liquefy and may eventually solidify.
C1
A3
C1
PAGE 11
Produced in partnership with the Association for Science Education
www.timstar.co.uk
KS3 CHEMISTRY:
Pure and Impure Substances
This is one of a series of documents designed to support science departments to integrate engaging and purposeful practical and investigative science activities within their current schemes of learning.
They highlight opportunities throughout the KS3 National Curriculum and identify possible purposes for each activity relating to the ‘Getting Practical’ project.
Possible practical activities
Purpose
Equipment Links
Stearic acid
ST5950
Thiele melting point
apparatus
ME10384
Investigating the melting and boiling points of an organic substance e.g. stearic acid and different
concentrations of stearic acid and sugar
This activity will show pupils that that mixtures do not have fixed melting or boiling points and to practise
key practical skills such as identifying variables, constructing a table, drawing a graph, pattern seeking
and drawing conclusion
A3
B2
C2
Melting point
apparatus
ME10351
Melting point tubes
75mm
ME10370
A temperature sensor attached to a computer could be used in this activity
Vision datalogger
DA130585
Temperature sensor
DA130870
Sodium chloride
Investigating the melting and boiling points of pure water and different concentrations of salt water
This activity will show pupils that that mixtures do not have fixed melting or boiling points and to practise
key practical skills such as identifying variables, constructing a table, drawing a graph, pattern seeking
and drawing conclusion
A temperature sensor attached to a computer could be used in this activity
A3
B2
C2
SO5528
Vision datalogger
DA130585
Temperature sensor
DA130870
PAGE 12
Produced in partnership with the Association for Science Education
www.timstar.co.uk