KS3 CHEMISTRY: Pure and Impure Substances … terms of Chemistry: Pure and impure substances all pupils will: name some soluble and insoluble solids; ... mixture, atom, composition,

KS3 CHEMISTRY:Pure and Impure Substances

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About this section of the curriculumPupils 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.

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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.

Produced in partnership with the Association for Science Education

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Learning demandThe 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-stage-three-national-strategy-training-materials

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Produced in partnership with the Association for Science Education

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.

www.timstar.co.ukProduced in partnership with the Association for Science Education

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

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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.

ExpectationsWithin 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

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Produced in partnership with the Association for Science Education

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

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Produced in partnership with the Association for Science Education

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 learningThrough 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

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PAGE 6

Produced in partnership with the Association for Science Education

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.

ResourcesResources include: Equipment Links:• simulation software, three-dimensional models to illustrate particle arrangement and movement in solids, liquids and gases

• samples of rocks that are mixtures

IGNEOUS ROCK SAMPLE PACKSMETAMORPHIC ROCK SAMPLES PACK CLASS ROCK SET

• 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

• temperature sensor and softwareVISION DATALOGGERTEMPERATURE SENSOR

• 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

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PAGE 7

Produced in partnership with the Association for Science Education

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 learningPupils could:

• visit libraries or museums to find out more about the mixtures of rock particles in different sedimentary rocks

• use 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

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Produced in partnership with the Association for Science Education

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 PracticalThe 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

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PAGE 9

Produced in partnership with the Association for Science Education

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.

www.timstar.co.uk

PAGE 10

Produced in partnership with the Association for Science Education

Possible practical activities Purpose Equipment Links

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

http://www.nuffieldfoundation.org/practical-chemistry/separating-sand-and-salt

A1 B1 A3 C2

Iron filings fine IR3206Sulphur fine powder SU6040Sand, fine white SA5278Sodium chloride SO5528Calcium carbonate precipitated CA1846Ink, brown CH90652Ink, royal blue CH90654Ink, green CH90656Ink, blue/black CH90660Chromatography sheets CH04020Bar 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:

• 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

A3 B2 C2

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

Sucrose SU6001Copper sulphate 5 water CO2260Thermometer -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

• which are compounds explain how air can be separated into its components

• describe some uses of the components of air

C1

Possible practical activities

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.

www.timstar.co.uk

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Produced in partnership with the Association for Science Education

Possible practical activities Purpose Equipment Links

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

Aluminium potassium sulphate 12 water AL1162Evaporating basin BA01626Watch glass WA17510Filter 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.

http://www.nuffieldfoundation.org/practical-chemistry/recovering-pure-water-solution-using-water-condenser

A3 B1 C1

14/23 Single joint set (BU’M set) JG93080Copper sulphate 5 water CO2260

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

Separating funnel 250ml FU08470Vegetable oil OI4408

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

http://www.nuffieldfoundation.org/practical-chemistry/extracting-iron-breakfast-cereal

B1 C1

Magnetic stirrer ST150510Stirring bar 25mm ST14425Stirring bar retriever ST14470Mortar and pestle 100mm MO11340Neodymium 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

C1

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.

A3 C1

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.

www.timstar.co.uk

PAGE 12

Produced in partnership with the Association for Science Education

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

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

A temperature sensor attached to a computer could be used in this activity

A3 B2 C2

Stearic acid ST5950Thiele melting point apparatus ME10384Melting point apparatus ME10351Melting point tubes 75mm ME10370Vision datalogger DA130585Temperature sensor DA130870

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

Sodium chloride SO5528Vision datalogger DA130585Temperature sensor DA130870