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KS3 SCIENCE-Chemistry QCA Unit 8F Compounds and mixtures

KS3 Quizzes or task sheets based on this summary: four word-fill worksheets * multiple choice quiz * X-word

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* KS3 Science multiple Choice Quizzes for chemistry, worksheets and practice chemistry questions for pupils revising Key Stage 3 science SATs tests revision help for secondary students *

More advanced GCSE work based on 8F: GCSE m/c tests * Atomic structure * Periodic Table * Chemical Bonding * Elements, Compounds, Mixtures and their Separation

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8F Compounds and mixtures

    QCA 8F "Compounds and mixtures" Multiple Choice Questions for Science SATs revision on comparing the properties and differences between elements, compounds and mixtures, melting and boiling points, idea of pure/impure.

8Fwf1-5 five handy linked word-fill worksheets * 8Fwf2 * 8Fwf3 * 8Fwf4 * 8Fwf5 *

The BIG hard on-line crossword puzzle (with letter hints), printout of the BIG version

OR the smaller EASIER (with letter hints), printout of the smaller EASIER version

matching pair quiz or drag-drop version-printout

The 8F crossword and word-fill

* KS3 Science multiple Choice Quizzes for chemistry, worksheets and practice chemistry questions for pupils revising Key Stage 3 science SATs tests revision help for secondary students *

In this unit you will learn to ..

• distinguish between elements and compounds and how they are represented by symbols and formulae - these show the relative numbers and types of atom present
• recognise chemical change as a process in which atoms join together in new ways
• distinguish between compounds and mixtures
• distinguish between chemical reactions in which new compounds are formed and the formation of mixtures
• investigate temperature changes as liquids cool
• use line graphs and choose appropriate scales for eg time, temperature or mass data.
• distinguish between elements, compounds and mixtures in terms of the particles they contain
• 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
• know mixtures do not change state at fixed temperatures

• can name some elements
• know that there are approximately 100 elements which are the building blocks for all materials
• know that elements are composed of tiny particles called atoms
• know that compounds are formed when atoms of different elements join
• have explored a number of chemical reactions
• have made and separated mixtures

• words with precise scientific meaning, eg element, compound, mixture, atom, composition, pure
• names of compounds, eg sodium carbonate, calcium chloride, hydrochloric acid

How are elements and compounds different?

• that elements contain only one kind of atom
• that compounds contain more than one kind of atom chemically bonded (joined) together
• that formulae indicate the (relative) numbers of atoms in a compound
• distinguish between elements and compounds in terms of names and symbolic formulae

How do compounds differ from the elements from which they are made?

• that compounds contain elements that are chemically combined
• that the properties of a compound are different from those of the elements from which it is made
• that a compound always contains the same elements in fixed proportions and relate this to interpreting formulae for compounds in terms of the relative numbers of atoms of different elements
• effect of heating a mixture of iron and sulphur powders in ignition tubes - a red glow and no yellow powder left after their tube has cooled - what evidence for suggesting chemical change - to extract the contents - does it still contains a mixture or if a new chemical (compound) has been made?  write a word, picture or symbol equations for the reaction
• show that the compound iron sulphide behaves differently from its constituent elements sulphur and iron, eg by adding a small amount of dilute acid to both and observing the differences in the way the mixture behaves compared to the compound.
• names of compounds eg water, carbon dioxide, copper carbonate - compare the compounds with the elements from which they are made - describe differences between compounds and the elements from which they are made
• consider the formulae of some of the oxides made in unit 8E ‘Atoms and elements’, eg magnesium, sodium and aluminium oxides, and the fact that compounds are made from elements in fixed proportions - pictures showing particles in examples of elements, compounds and various mixtures of elements and/or compounds

Do compounds react chemically?

• that compounds can react chemically
• observe a number of test tube chemical reactions in which visible changes occur, eg mixing sodium carbonate solution and iron(II) chloride solution; adding dilute hydrochloric acid to solid magnesium carbonate; adding dilute ammonia solution to copper sulphate solution; heating sucrose
• identify appropriate indications of chemical reactions
• state that chemical reactions took place between the compounds
• note that some physical changes also involve colour changes and gas evolution, and that a chemical reaction is distinguished by changes in the ways the atoms are bonded together.

Are there other sorts of material besides elements and compounds?

• reminder about differences between compounds and mixtures eg in unit 7H ‘Solutions’ and show them examples of mixtures they may have encountered, eg iron and sulphur, chalk in water, seawater, air, soil, rocks, ink, shaving foam
• and drawing diagrams to illustrate the particles in elements and compounds and extending this to mixtures
• criteria for deciding whether something is a mixture or not
• the idea that compounds can be represented by a formula whereas mixtures vary in composition and have no fixed formula, eg by showing samples of compounds together with molecule models, and contrasting these with samples of mineral water which is a mixture
• the meaning of ‘pure’ when applied to a material, eg What is ‘pure’ orange juice? What is ‘pure’ water?
• what is meant by ‘pure’ and ‘impure’ and link to eg the illustrations of elements, compounds and mixtures made earlier in the activity
• name some everyday mixtures, eg air (gases), seawater and mineral water (which are both liquid water containing dissolved gases and solids)
• identify that mixtures (eg above) can vary in composition and can be separated (eg in unit 7H ‘Solutions’)
• the idea of rocks as mixtures is explored more fully in unit 8G ‘Rocks and weathering’ and unit 8H ‘The rock cycle’ but handy to use the same rock samples in this activity
• name the main gases present in air and give approximate proportions of these (the particles maybe element atoms, element molecules and compound molecules)
• explain clearly how air can be separated into its components - if cooled enough under pressure it will liquify
• describe clearly some uses of the components of air
• related work on photosynthesis and respiration in unit 8B ‘Respiration’, unit 9B ‘Fit and healthy’ and unit 9C ‘Plants and photosynthesis’, and air pollution in unit 9G ‘Environmental chemistry’.
• that elements and compounds melt and boil at particular temperatures and the temperatures are characteristic of these substances (note boiling point is always above the melting point!)
• that mixtures do not melt or boil at fixed temperatures
• look back at work on elements in unit 8E ‘Atoms and elements’ and to identify boiling points and melting points of some of these elements - note very high temperatures at which some metals melt
• demonstration of the differences in the boiling point of tap water and salt solution which illustrates that mixtures do not have fixed melting or boiling points and they are different than the values for pure substances
• describe how the melting point or boiling point of a mixture varies with composition
• a temperature line was constructed in unit 8I ‘Heating and cooling’ - can investigate how temperature changes as they cool (surrounded by an ice/salt mixture) liquids eg pure and impure stearic acid.