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Patterns of reactivity

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Unit guide

Where this unit fits in

Prior learning

This unit builds on: unit 8E Atoms and elements, unit 8F Compounds and mixtures and unit 9E Reactions of metals and metal compounds. Ideas in this unit are developed further in 9G Environmental chemistry and 9H Using chemistry.

To make good progress, pupils starting this unit need to: • be able to explain explain the differences differences between elements and compounds • have represented elements elements and compounds by symbols and formulae • have represented chemical chemical reactions by word questions • know that many many metals react with oxygen to form oxides • be able to make generalisations generalisations about the reaction of metals with acids.

The concepts in this unit are: different metals show similar reactions reactions but the rate of reaction varies; metals can be arranged in order of reactivity – the reactivity series is a very useful tool for understanding and predicting metal reactions.

This unit leads onto: work in key stage 4 on metals and their compounds.

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This unit relates to: unit 9E Reactions of metals and metal compounds.

Framework yearly teaching objectives – Particles • Identify Identify evidence which indicates that a chemical reaction has taken place, such as the association of energy transfer with chemical change. • Recognise that chemical reactions reactions can be modelled by assuming that atoms can rearrange themselves, themselves, and that this can happen in only a limited number of ways, for example: A + B→ AB, AB + CD → AD + CB. • Use the particle rearrangement rearrangement model to: predict the names and formulae for products products that might be formed from given reactants; write word and symbol equations for some simple reactions. • Identify Identify differences in reactivity of metals to construct construct a reactivity series; use this to explain uses of metals and make predictions predictions about the reactions of metals.

Expectations from the QCA Scheme of Work At the end of this unit …

… some pupils will not have made so much progress and will …

… most pupils will …

… some pupils will have progressed further and will …

in terms of scientific enquiry NC Programme of Study Sc1 2b, c, d, e, f, g, h, i, j, m, o • select and make effective use of secondary sources sources about the origins and uses of metals • identify identify relevant observations and describe patterns in these • suggest a workable approach approach to investigating the the reaction of metals with acids, identifying variables to be controlled • explain results using scientific scientific knowledge knowledge and understanding.

• select information information from secondary sources about the origins and uses of metals • describe observations observations and identify where there are similarities • suggest how reaction reaction with acids might might be investigated, investigated, controlling controlling variables identified for them • relate results to scientific knowledge knowledge and understanding.

• synthesise information information from secondary sources • point out where where reactions do not fit the pattern expected.

in terms of materials and their properties NC Programme of Study Sc3 1d, 3a, b, c, d, h • identify identify and describe similarities in chemical reactions • identify identify differences in the reactivity of different metals and use these to explain some everyday uses and occurrence of metals • represent chemical reactions reactions by word equations.

• describe how some metals metals react with water, • use the reactivity series to make predictions predictions acids and oxygen about the reactions of metals • give some uses of metals, relating these these to • relate the reactivity reactivity of a metal to its uses, the reactivity of the metal. how it occurs and when it was first extracted and used • represent represent some reactions by symbol equations. equations.

Suggested lesson allocation (see individual lesson planning guides) Direct route F1

F2

F3

Losing that shine

Corrosivee liquids Corrosiv

Changing places

F4

F5 Who’s top of the Reactivity league? in action

F6

Booster 4

Variables together together – Think about variables that interact

Focus on particles 2 – Chemical changes

Extra lessons (not in Pupil book) Review and assess progress (distributed appropriately)

Misconceptions Pupils often think that a faster reaction produces more product rather than simply getting to the same end point sooner. Additional information The anomalous position of aluminium has not been introduced in this unit. Health and safety (see activity notes to inform risk assessment) Risk assessments are required for any hazardous activity. In this unit pupils observe reactions of alkali metals, use metals, acids and solutions of salts which may be hazardous and also use flammable metals and observe what happens when they burn. They observe the thermit reaction, work with coarse mesh filings of metals and plan and carry out their own investigation into the reaction of metals with acids. © Harcourt Education Education Ltd 2004 Catalyst 3 This wor This work kshe hee et ma may ha hav ve be bee en alte altere red d fro from m the the or orig igin ina al on th the e CDCD-R ROM.

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Lesson planning guide

Learning objectives i Find Find out out what what happ happens ens when when meta metall react reactss with with oxyg oxygen. en. ii Metals Metals react react with oxyge oxygen n at differen differentt rates and and release release differe different nt amoun amounts ts of energy energy.. iii Be able to to write word word equati equations ons for for the the reaction reaction of of metals metals with oxygen oxygen.. iv Atom Atomss contai contain n electr electron onss and and proto protons ns.. (extension (extension only ) Scientific enquiry v Use informa information tion about about the the corrosion corrosion of metal metal objects objects to sugges suggestt patterns patterns.. (Framework (Framework YTO YTO Sc1 9f)

Suggested alternative starter activities

(5–10 minutes)

Introduce the unit

Share learning objectives

Brainstorming

Unit map for Patterns of reactivity.

• Describe what happens when metals corrode. • Explain patterns patterns in the the way metal objects corrode. (Sc1)

Pupils consider the life of an iron bridge. Catalyst Interactive Presentations 3

Capture interest (1)


Show pupils fake gold jewellery and discuss whether it will corrode.

Show photos of different metals and discuss how they change over time. Catalyst Interactive Presentations 3

Suggested alternative main activities Activity

Learning objectives see above

Description

Approx. timing

Textbook F1

i, ii and iii

Teacher-led explanation and questioning OR Pupils work individually, in pairs or in small groups through the in-text questions and then onto the end-of-spread questions if time allows.

Activity F1a Practical

i, ii and iii

Reactive metals and oxygen Demonstration of reactions of more reactive metals with oxygen.

Activity F1b Paper

i, ii, iii and v Tarnished metal Pupils answer questions about gold, iron and chromium corroding under different conditions.

Activity F1c Paper

iv

Inside the atom The most able pupils are introduced to the concept of atomic structure.

Suggested alternative plenary activities

Target group C

H

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20 min

R/G

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10 min

✔

20 min

✔

15 min min

✔

(5–10 minutes)

Review learning

Sharing responses

Group feedback

Word game

Looking ahead

Pupils make key fact cards and use them to test each other.

Whole-class discussion summarising ideas about what causes metals to corrode at different rates.

Pupils combine into larger groups to compare their responses to Activity F1b.

Pupils complete sentences with missing words to show key points of lesson.

Pupils think about other substances that react with metals using the context of an iron bridge. Catalyst Interactive Presentations 3

Learning outcomes Most pupils will ...

Some pupils, making less progress will ...

Some pupils, making more progress will ...

• appreciate that different different metals react with oxygen • recall the basic metal/oxygen metal/oxygen reaction. at different rates • link rate of reaction reaction to reactivity • appreciate that more more reactive metals release more energy.

• understand understand and apply the concept of reactivity in a wider range of situations.

Key words oxide, reactive, unreactive, reactivity

Out-of-lesson Out-of-lesson learning Homework F1 Textbook F1 end-of-spread questions Activity F1b Activity F1c

© Harcourt Education Education Ltd 2004 Catalyst 3 This wor This work kshe hee et ma may ha hav ve be bee en alte altere red d fro from m the the or orig igin ina al on th the e CDCD-R ROM.

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Losing that shine

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Learning objectives i Find Find out out what what happ happens ens when when meta metall react reactss with with oxyg oxygen. en. ii Metals Metals react react with oxyge oxygen n at differen differentt rates and and release release differe different nt amoun amounts ts of energy energy.. iii Be able to to write word word equati equations ons for for the the reaction reaction of of metals metals with oxygen oxygen.. iv Atom Atomss contai contain n electr electron onss and and proto protons ns.. (extension (extension only ) Scientific enquiry v Use informa information tion about about the the corrosion corrosion of metal metal objects objects to sugges suggestt patterns patterns.. (Framework (Framework YTO YTO Sc1 9f)


(5–10 minutes)

Introduce the unit


Brainstorming


• Describe what happens when metals corrode. • Explain patterns patterns in the the way metal objects corrode. (Sc1)








Description

Approx. timing

Textbook F1

i, ii and iii



i, ii and iii

Reactive metals and oxygen Demonstration of reactions of more reactive metals with oxygen.

Activity F1b Paper

i, ii, iii and v Tarnished metal Pupils answer questions about gold, iron and chromium corroding under different conditions.

Activity F1c Paper

iv

Inside the atom The most able pupils are introduced to the concept of atomic structure.


Target group C

H

E

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20 min

R/G

G

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10 min

✔

20 min

✔

15 min min

✔

(5–10 minutes)

Review learning

Sharing responses

Group feedback

Word game

Looking ahead

Pupils make key fact cards and use them to test each other.

Whole-class discussion summarising ideas about what causes metals to corrode at different rates.

Pupils combine into larger groups to compare their responses to Activity F1b.

Pupils complete sentences with missing words to show key points of lesson.

Pupils think about other substances that react with metals using the context of an iron bridge. Catalyst Interactive Presentations 3




• appreciate that different different metals react with oxygen • recall the basic metal/oxygen metal/oxygen reaction. at different rates • link rate of reaction reaction to reactivity • appreciate that more more reactive metals release more energy.

• understand understand and apply the concept of reactivity in a wider range of situations.

Key words oxide, reactive, unreactive, reactivity

Out-of-lesson Out-of-lesson learning Homework F1 Textbook F1 end-of-spread questions Activity F1b Activity F1c


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Corrosive Corrosive liquids

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Learning objectives i Find Find out out what what happ happen enss when when meta metall reac reacts ts with with acid acid.. ii Find Find out out what what happen happenss when when metal metal reac reacts ts with with wate waterr. iii Metals Metals react react with acid and water water at different different rates. rates. iv Electron Electronss are arrang arranged ed in shells shells roun round d the nucleus nucleus of of an atom. atom. (extension (extension only ) Scientific enquiry v Describe Describe pattern patternss in the reacti reactivity vity of of metals metals using using experimen experimental tal data. data. (Framew (Framework ork YTO YTO Sc1 9f) vi Present Present observ observatio ations ns usin using g tables. tables. (Framewo (Framework rk YTO YTO Sc1 9e)


(5–10 minutes)

Recap last lesson


Problem solving

Quick quiz in groups about metals reacting with air.

• Describe what happens Chemical changes in a when metals react with blacksmith’s. water and acids. • Predict how how reactive a metal is from experimental experimental observations. (Sc1)

Brainstorming

Capture interest

Corrosion of coins in treasure chests.

Show a video clip of reaction of group I metals, including rubidium and caesium, with water. water. Catalyst Interactive Presentations 3



Description

Approx. timing

Textbook F2

i and ii



i, ii, iii, v and vi

Reacting metals with water Pupils watch a demonstration and

Target group C

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20 min

R/G

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10 min

✔

answer questions.

Activity F2b Practical

i, iii and v

Reacting metals with acids Pupils carry out an experiment to react metals with dilute hydrochloric acid.

15 min

✔

✔

(✔)

Activity F2c ICT

i and ii

Relatively reactive Pupils use a database to classify metals in order of reactivity.

15 min

✔

✔

✔

Activity F2d Paper

iv

Electrons in atoms The most able pupils are encouraged to make the 15 min link between the periodic table and the arrangement of electrons in atoms.


✔

(5–10 minutes)

Review learning

Sharing responses

Group feedback

Word game

Looking ahead

True/false quiz.

Pupils work in groups to discuss the outcomes of Activity F2b.

Whole group discussion relating to safety precautions when working with metals and acids.

Play ‘What am I?’ to guess the metal.

Class discussion about trends in reactivity.



• understand understand the basic metal/acid reaction • recall the basic metal/acid metal/acid reaction reaction • appreciate that more more reactive metals produce produce the • recall that some metals react with water. water. same amount of hydrogen faster rather than producing more hydrogen (all else being equal) • understand understand that some metals react with water, but that this is a slower reaction than that with acid.

Key words corrosive, acid, salt, red only : base, alkali

Some pupils, making more progress will ... • appreciate the emergent emergent pattern of reactivity.

Out-of-lesson Out-of-lesson learning Homework F2 Textbook F2 end-of-spread questions Activity F2d


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Changing places

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Learning objectives i A simple model for displacement reactions. ii How relative reactivity controls displacement. iii Atoms can gain or lose electrons during a reaction. (extension only ) Scientific enquiry iv Observe patterns in data. (Framework YTO Sc1 9f) v Use data to make interpretations and recognise the importance of negative results.


(5–10 minutes)

Recap last lesson


Problem solving

Word game

Capture interest

Whole group discussion focusing on how the reactivity of metals varies.

• Describe what happens in metal displacement reactions. • Use a simple model to explain how reactivity affects displacement reactions. (Sc1)

Pupils use their knowledge of metal reactions to suggest tests to identify five different metals.

Matching exercise to match substances with their descriptions.

Demo of copper-plating iron objects.



Description

Approx. timing

Textbook F3

i and ii



Target group C

H

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R/G

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i, ii, iv and v Displacement reactions Pupils investigate displacement reactions of 20 min three metals.

✔

✔

Activity F3b Practical

i, ii, iv and v Displacement in action Pupils carry out displacement reactions to plate metals.

✔

Activity F3c Paper

iii

Atoms and ions The most able pupils look at what happens in terms of electrons during displacement reactions.


20 min

15 min 15 min

✔

(5–10 minutes)

Review learning

Sharing responses

Group feedback

Word game

Game to predict if a reaction will happen between named pairs of metals and metal compounds.

Pupils feed back their outcomes of Activity F3a and discuss why negative results are important in experiments.

Groups make short Anagram game. presentations to show their ideas about displacement from Activity F3b.

Looking ahead Pupils are asked to suggest one metal that would displace all the metals used today, and one that would not.



• understand qualitatively what happens in a • appreciate that some metals can push others displacement model using the ‘reaction race’ analogy out of their compound • understand that a more reactive metal will • know that displacement reactions can release displace a less reactive metal from its compound a lot of energy • know that displacement reactions can release a lot • be able to use patterns of reactivity to of energy explain displacement reactions. • appreciate that the ‘reactions race’ idea can be used to stop iron rusting.

Key words displace, displacement reaction

Some pupils, making more progress will ... • use the particle model to understand what is happening in a displacement reaction • appreciate what is shown by a balanced chemical equation • recognise that negative results are useful to prove a pattern.

Out-of-lesson learning Homework F3 Textbook F3 end-of-spread questions Activity F3c

©Harcourt Education Ltd 2004 Catalyst 3 This worksheet may have been altered from the original on the CD-ROM.

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Who’s top of the league?

F4


Learning objectives i Know about the reactivity series. ii Know that a more reactive metal can displace a less reactive metal from its compounds.

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Scientific enquiry iii Draw conclusions from data, interpreting patterns and using them to make predictions. (Framework YTO Sc1 9f) iv Present and interpret observations using charts. (Framework YTO Sc1 9e)

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UG

(5–10 minutes)

Recap last lesson Share learning objectives

Problem solving

Brainstorming

Quick quiz about displacement reactions.

Pupils work out the relative reactivity of lead and zinc from a demonstration of displacement.

In groups, pupils Making an ‘initial badge’ by discuss how to find displacement. out the reactivities of different metals.

• State the reactivity series for some metals. • Predict what displacement reactions will work using the reactivity series. (Sc1)

Capture interest



Description

Approx. timing

Textbook F4

i and ii


Activity F4a Paper

i, ii, iii and iv

Using reactivity data Pupils use data from two experiments, one involving temperature change, to rank metals in order of reactivity.

Target group C

H

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20 min

R/G

G

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30 min

✔

(✔)

Advance warning Tell pupils which metal they will be researching in Activity F5a. Ask them to carry out web searches to find information on its properties, uses and extraction.


(5–10 minutes)

Review learning

Sharing responses

Group feedback

Word game

Looking ahead

The class produces a list of key facts about metal reactivity.

Pupils compare the outcomes of Activity F4a.

Group work to make reactivity series display.

Play ‘React or not?’ card game.

Pupils discuss how to choose the right metal for the job.



• use the data given to arrange the ten metals into a correct reactivity series • use this reactivity series to make predictions.

• appreciate that metals can be arranged in order • appreciate the wider significance of the according to their reactivity. reactivity series and how it may be applied • be able to suggest experiments to deduce the reactivity of different metals.

Key words reactivity series


Out-of-lesson learning Homework F4 Textbook F4 end-of-spread questions Activity F4a


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Reactivity in action

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Learning objectives i How the reactivity series can be used. ii How reactivity and metal properties affect the way metals are used. Scientific enquiry iii Apply recognised patterns to understand/predict metal usage. (Framework YTO Sc1 9f) iv Search for and choose secondary data to explain the uses of metals. (Framework YTO Sc1 8d)


(5–10 minutes)

Recap last lesson


Problem solving (1)

In groups pupils write definitions of key words.

• Explain why different metals are How can copper be chosen for different jobs. reclaimed from spoil • Select relevant information about heaps? metals using different sources. (Sc1) • Select a suitable method of presentation to communicate information. (Sc1)



Show photos of the range, uses and extraction of metals. Catalyst Interactive Presentations 3

Demonstration of thermit reaction. Catalyst Interactive Presentations 3



Description

Approx. timing

Textbook F5

i and ii


Activity F5a Discussion

i, ii, iii and iv

Uses of metals Pupils research the extraction and uses of metals and 30 min make a presentation.


20 min

Target group C

H

E

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R/G

G

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✔

✔

✔

(5–10 minutes)

Review learning

Sharing responses

Group feedback

Word game

Looking back

Brainstorm of how metals are used.

Presentations of outcomes of Activity F5a.

Groups combine to discuss how they carried out their research in Activity F5a.

Pupils match metals to their Pupils revise and uses. consolidate knowledge from the unit.



• understand how metal reactivity affects • appreciate why some metals are used for the uses to which metals may be put particular purposes • understand how the reactivity series can • be able to find out facts about a metal. be used to get metals from their compounds • be able to carry out focused research.

Key words None

Some pupils, making more progress will ... • understand how metal discovery was closely linked to the reactivity series • research complex ideas and be selective about which information to use • be able to use the reactivity series to make predictions.

Out-of-lesson learning Homework F5 Textbook F5 end-of-spread questions Read fiction and poems, e.g. Charcoal Burners, about the search for metals


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Variables together – Think about variables that interact

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Learning objectives i Know how iron rusts and that the two variables interact. ii Know that some conditions make iron rust faster. iii Know some techniques for rust prevention. The structure of this lesson is based around the CASE approach. The starter activities give concrete preparation. The main activities move away from the concrete towards a challenging situation, where pupils need to think. The extended plenary gives pupils time to discuss what they have learnt, to negotiate a method to commit to paper and express their ideas verbally to the rest of the class. Scientific enquiry iv Consider strategies used when planning experiments. (Framework YTO Sc1 9b) v Draw conclusions from data and appreciate the limitations of the data. (red only ) (Framework YTO Sc1 9g)


(5–10 minutes)

Bridging to the unit

Setting the context

Concrete preparation

Display of corroded objects to link to previous lessons.

Show car adverts and discuss why it is important to understand rusting.

Using a bike as an example, pupils make a list of factors that may affect whether or not iron rusts.



Description

Textbook F6

i, ii and v



i, ii, iii, iv and v

Variables in rusting Pupils analyse the results of an experiment set up to investigate rusting.


Approx. timing

Target group C

H

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30 min

R/G

G

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20 min

✔

(5–10 minutes)

Group feedback

Bridging to other topics

Groups feed back to the whole group on the outcomes of their investigations.

Focus on variables that interact in rusting and in other examples in science.



• interpret the data so that they understand how it shows that both oxygen and water are needed to make iron rust • be able to suggest some strategies for investigating rust prevention.

• know that both oxygen and water are needed to • appreciate the limitations of given data and make iron rust suggest ways to improve the investigation • know that using a barrier to oxygen and water • be able to develop a complex strategy for stops iron rusting. investigating multiple variables that affect the rusting of iron • be able to interpret their results to evaluate rust prevention techniques and identify factors that increase rate of rusting.

Key words variable, interact, red only: independent, dependent


Out-of-lesson learning Textbook F6 end-of-spread questions


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Patterns of reactivity

Unit map

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Preventing rusting

Metals reacting with air

Patterns of reactivity Reactivity series and uses of metals

Metals reacting with water and acids Metals displacing metals

Copy the unit map and use these words to help you complete it. You may add words of your own too. copper corrosion displacement energy extraction gold hydrogen iron less reactive metal hydroxide


metal oxide more reactive ore oxygen potassium rusting salts temperature thermit reaction

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Losing that shine

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Starters

Suggested alternative starter activities (5–10 minutes) ?

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UG LP

Introduce the unit


Brainstorming


• Describe what happens when metals corrode. • Explain patterns in the way metal objects corrode. (Sc1)






Introduce the unit 



Either draw the outline of the unit map on the board then ask pupils to give you words to add, saying where to add them. Suggest some words yourself when necessary to keep pupils on the right track. Or give out the unit map and ask pupils to work in groups deciding how to add the listed words to the diagram. Then go through it on the board as each group gives suggestions.

➔ Unit map

Share learning objectives 

Write learning objectives on the board and illustrate why it is important that we know about these ideas.



Tell pupils that iron is used in far greater amounts than any other metal, e.g. in cars, electrical appliances, bridges, machinery in factories, buildings etc. However, it has to be replaced because it rusts away so that the products or machinery are unsafe or stop working.



Understanding why metals corrode has helped scientists and engineers develop methods of preventing corrosion, e.g. most cars have a 5 year anti-corrosion warranty because the iron undercarriage is now sealed in plastic, oil protects the engine and the bodywork is sealed in zinc and paint to stop corrosion.

Brainstorming Show pupils the photograph of the iron bridge. A local alternative could be used.

➔ Catalyst Interactive



Write the suggested questions on the board. Ask pupils to work in groups to brainstorm their ideas and then feed back to the class.



Focus discussion on the idea that iron reacts to form rust and that this can be prevented by coating the iron in an airtight coating (most modern bridges are alloyed).

Questions 1 Why is iron a good material for building bridges? 2 What changes happen as the bridge gets older? Why do they happen? 3 How long will the bridge last? 4 What can be done to make a bridge last longer?



Capture interest (1) 

Show pupils a display of ‘gold’ cheap jewellery and compare prices to real gold in a catalogue.



Discuss the cost of real versus fake and what will happen to the cheap ‘gold’.



Discuss the idea that ‘cheap’ jewellery often contains cheaper metals like iron that react with substances in the air (and people, which causes allergic reactions). Gold does not react.


Show pupils photos of metal objects of different ages.



Ask them why they think metal objects corrode at different rates.



Focus on the idea that different metals corrode at different rates, and the conditions they are under can affect the rate of change.


Presentations 3

Equipment cheap ‘gold’ jewellery (it does not matter if it is already tarnished); pictures of real gold jewellery in a catalogue showing prices ➔ Catalyst Interactive

Presentations 3

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Corrosive liquids

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Recap last lesson


Quick quiz in groups about metals reacting with air.

• Describe what happens when Chemical changes in a metals react with water and blacksmith’s. acids. • Predict how reactive a metal is from experimental observations. (Sc1)

UG LP

Problem solving

Brainstorming

Capture interest

Corrosion of coins in treasure chests.

Show a video clip of reaction of group I metals, including rubidium and caesium, with water. Catalyst Interactive Presentations 3

Recap last lesson 

Write the questions on the board.



Pupils work in pairs to answer the questions.



Pairs combine into a group of four to compare answers.



A spokesperson feeds back any areas of uncertainty to whole class as a short plenary.


Ask pupils to write a list of FAQs they would put on a website telling people about acids. Collect suggestions as a whole-class activity, steering pupils towards those related to the objectives. Conclude by highlighting the questions you want them to be able to answer at the end of the lesson.

Questions 1 Why does gold stay shiny but iron goes rusty very quickly? 2 Why are sodium and potassium stored in dark jars full of oil? 3 What is used up in the air when shiny zinc goes dull? 4 Magnesium is used to make blue flashes in fireworks. It reacts with oxygen. What does magnesium make when it reacts with oxygen? Answers 1 Gold is unreactive; iron is much more reactive; 2 The jars keep light, water and oxygen away from the very reactive metals; 3 oxygen; 4 Magnesium oxide.

Problem solving 

Remind pupils of the differences between physical (e.g. no new substances made, can be easily reversed, for example, state changes) and chemical (e.g. new substances made, not easily reversed) changes.



Pupils look at the contexts described on the pupil sheet. They decide which is a chemical and which is a physical change and give evidence for their ideas.



They should realise that the re-shaping of iron is a physical change, but rusting is a chemical change.

➔ Pupil sheet

Brainstorming 



Tell pupils that two treasure chests of ancient gold and metal coins have been found – one on land, one in the sea. Ask them what they expect to see when they open the chests. Make a list of their ideas on the board. Focus discussion on the idea that most metals corrode much faster in water (after 100 years, very few metal objects are left on the Titanic , for example) than in air, but very unreactive metals, such as gold, do not corrode at all.

Capture interest 

Pupils watch video clips of very reactive metals reacting with water. Compare this to the much slower processes of more common metals corroding in wet conditions.


➔ Catalyst Interactive Presentations 3

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XX F2

Corrosive liquids

Starters

Problem solving

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Joe is a blacksmith. He makes iron shoes for horses.

UG LP TN

Joe heats iron until it is so hot that it can easily be bent to fit the horse's foot. When it cools down it looks grey and shiny.

Joe has some old shoes in his shop. They used to be grey and shiny but are now covered in lumps of red rust. Questions

Which change in Joe’s shop is a physical change ? Which is a chemical change ? 2 Use ideas from the diagrams to explain how you can tell. 1


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Changing places

F3 M

Starters


Recap last lesson


Problem solving

Word game

Capture interest

t

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Whole group discussion focusing on how the reactivity of metals varies.

Demonstration of copperplating iron objects

_

Pupils use their knowledge of metal reactions to suggest tests to identify five different metals.

Matching exercise to match substances with their descriptions.

^

• Describe what happens in metal displacement reactions • Use a simple model to explain how reactivity affects displacement reactions. (Sc1)

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UG LP


Ask pupils to suggest ways that different metals behave differently.



Use pupil responses to make a list on the board.



Encourage pupils to think in terms of the differences in reactions of more reactive and less reactive metals.



Focus on the difference in reactivity of metals with oxygen, water and acids.


Write learning objectives on board and illustrate why it is important that we know about these ideas.



Tell pupils that when metals are taken from the ground they are usually in the form of compounds in rocks. Engineers and scientists use data about the reactivity of the metals to decide how to extract the useful metal and what metals are suitable to use for different purposes.

Word game 

Pupils link each substance to the correct description on the pupil sheet.

➔ Pupil sheet

Answers copper: 4; hydrogen: 3; iron: 2; oxygen: 1; sodium: 5; sulphuric acid: 6

Problem solving 



Tell pupils to think about five grey metals: sodium, silver, calcium, magnesium and iron. Ask them to work in small groups to make a list of tests they could do, with the results they would expect, to prove which is which.

Answers Suggestions should include testing with water or acid, or leaving for a week or so in air.


Put an iron object, such as a key, into a petri dish containing dilute copper sulphate (it is best to use ‘one I made earlier’ as this takes a few minutes to work).

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Show pupils that the key has become plated with copper.

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Equipment petri dish containing dilute (approx 1 mol/dm3 will work) copper sulphate; iron object such as a key

Tell them that this has happened because iron and copper have different reactivities.


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Changing places

F3

Starters

Word game

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Match these words to the correct descriptions.

copper

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hy dr ogen

iron

ox ygen

sulphur ic acid

sodium

UG LP TN

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I react with metals to make them look dull.

I react slowly with acids.

I am a gas that fizzes when metals react with acids.

4

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I am a lazy metal that does not react with acids.

I am a metal but don’t touch me! I am so reactive I will burn your fingers!

I make metal sulphates when I react with metals.


Sheet 1 of 1

Changing places

F3

Starters

Word game Match these words to the correct descriptions.

copper

hy dr ogen

iron

ox ygen

sulphur ic acid

sodium

1

2

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I react with metals to make them look dull.

I react slowly with acids.

I am a gas that fizzes when metals react with acids.

4

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I am a lazy metal that does not react with acids.

I am a metal but don’t touch me! I am so reactive I will burn your fingers!

I make metal sulphates when I react with metals.


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UG LP

Recap last lesson


Problem solving

Brainstorming

Capture interest

Quick quiz about displacement reactions.

• State the reactivity series for some metals. • Predict what displacement reactions will work using the reactivity series. (Sc1)

Pupils work out the relative reactivity of lead and zinc from a demonstration of displacement.

In groups, pupils discuss how to find out the reactivities of different metals.

Making an ‘initial badge’ by displacement.


Pupils write down their answers to verbal questions.

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Ask pupils to mark each other’s answers. Groups feed back by a spokesperson raising a hand to identify which questions more than one person in their group answered wrongly.


Ask pupils to write a list of FAQs they would put on a website telling people about displacement. Collect suggestions as a whole-class activity, steering pupils towards those related to the objectives. Conclude by highlighting the questions you want them to be able to answer at the end of the lesson.

Questions 1 What is the word for when zinc pushes copper out of copper sulphate solution? 2 What metal is made when zinc reacts with copper sulphate solution? 3 We use this piece of equipment to show that energy is given out when zinc reacts with copper sulphate solution. 4 Name one metal that will not react with copper sulphate solution. 5 Magnesium is very reactive. Does magnesium react with copper sulphate? Answers 1 displacement; 2 copper; 3 thermometer/ temperature probe; 4 gold/silver/copper; 5 yes

Problem solving 

Demonstrate the displacement of lead by dipping a cleaned zinc strip in a solution of lead nitrate in a boiling tube.

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Ask pupils to work in groups to decide which is the most reactive metal, lead or zinc.

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Ask pupils to suggest some other experiments to prove this.

➔ Teacher and technician sheet

Brainstorming 

Allow pupils time in their groups to think of some ideas to answer the question. Ask a spokesperson from each group to feed back ideas and make a whole class summary on the board.

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Look for several methods, e.g. rates of tarnishing, reaction with oxygen, water, acids and displacement reactions, measuring energy changes during reactions.

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For less able pupils, it may be simpler to give actual examples of metals for them to think about, e.g. ‘How can you tell that sodium is more reactive than iron?’.

Question 1 How can you find out the reactivities of different metals?


Show pupils how an ‘initial badge’ can be made by displacement.


➔ Teacher and technician sheet

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F4

Problem solving

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Starters Wear eye protection.

Teacher and technician sheet

zinc strip

Lead nitrate is toxic, avoid contact with skin.

UG LP TN

boiling tube

lead nitrate Equipment 

lead nitrate (0.4 mol/dm3)

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zinc strip cleaned as described in Activity F3b

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boiling tube and rack

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(optional) digital microscope and light projector

1 Show pupils the displacement of lead by zinc (it is best to set this up in advance to get larger crystals forming). A digital microscope can be used to show the crystals of lead forming on the zinc strip. 2 Write the equation for the reaction on the board (more able pupils can be asked to deduce the right hand side). zinc +lead nitrate → lead +zinc nitrate 3 Ask them to consider the answers to these questions in their groups. Which is more reactive, lead or zinc? [zinc] What other experiments could you do to prove it? [add lead to zinc nitrate – no reaction; add both metals to dilute acid, zinc reacts faster; watch tarnishing reaction in air, zinc reacts faster]


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F4

Starters

Capture interest

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zinc strip

zinc strip

UG LP TN

clear nail varnish

copper sulphate solution initial

boiling tube

Equipment 

copper sulphate (1 mol/dm3)

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zinc strip cleaned as described in Activity F3b

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boiling tube and rack

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clear nail varnish

1 Write an initial on the zinc strip using clear nail varnish. 2 Ask pupils to predict what will happen when the strip is left in copper sulphate solution. 3 Carry out the demonstration – after a few minutes the zinc will be copper plated, but the protected area will stay silver coloured.


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Recap last lesson


Problem solving



In groups pupils write definitions of key words.

• Explain why different metals are chosen for different jobs. • Select relevant information about metals using different sources. (Sc1) • Select a suitable method of presentation to communicate information. (Sc1)

How can copper be reclaimed from spoil heaps?

Show photos of the range, uses and extraction of metals. Catalyst Interactive Presentations 3

Demonstration of thermit reaction. Catalyst Interactive Presentations 3

UG LP


Write the key words that the pupils have met so far in the topic on the board.

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Pupils work in small groups to write down what they think each term means.

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Ask a spokesperson to feed back and summarise an acceptable explanation for each term on the board.

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Pupils copy the whole-class summaries to keep for revision.

Key words displacement, metal reactivity, corrosive, corrosion, salt


Write learning objectives on board.

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Ask pupils to brainstorm what metal objects they have used so far in their day.

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Highlight that for each purpose the ‘right’ metal needs to be chosen or these various objects would not work or would have too short a lifespan. This illustrates that it is important to know how metals react.

Problem solving 

Pupils look at the description of reclaiming copper from waste spoil heaps on the pupil sheet (this can be shown as an OHT) and work through the task.

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Possible ideas include, concentrating by evaporation (cheap in hot countries, no fuel needed), add iron (cheap metal more reactive than copper). M ore able pupils may take this further by suggesting filtration to remove the copper formed. Excess iron in the copper can be removed by reacting it with dilute acid. (This process is already in use – it involves bacterial leaching.)

➔ Pupil sheet


Show pupils the photographs. Highlight the huge scale of the uses of metals and how important they are to our lives, work and wealth.

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Explain that most examples use alloys that are mixtures of metals: this alters the properties of the material.

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Focus on the huge range of uses for metals in industry and the importance of choosing the right metal for each use to ensure that the products function properly and have an appropriate lifespan.


Presentations 3


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Demonstration of the thermit reaction to illustrate the ideas covered in the book.

➔ Teacher and

Show pupils photo of the thermit reaction being used.


technician sheet Presentations 3


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F5

Problem solving

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Copper is very expensive. Supplies of copper in the ground are running out. Scientists are working to devise a way of reclaiming u copper from waste heaps. _

UG LP

This diagram shows the first stage of the process. The process needs to work on a very big scale so needs to be cheap.

TN

spray with dilute sulphuric acid waste heap containing tiny amounts of copper compounds water running off contains very dilute copper sulphate solution

Your task is to work out how copper can be made from the very dilute copper sulphate solution. Work as a group to think about the problem. You need to consider... 

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The solution is very dilute and needs to be made more concentrated. How can you do this cheaply? What can you add to copper sulphate that will react to form copper? (Hint – think displacement!) Think about cost in your answer. How could you get clean copper solids after the reaction has finished? Choose a spokesperson to feed back your ideas to the whole class.


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Wear eye protection.


magnesium ribbon

UG LP

Carry out the reaction behind tall safety screens.

iron oxide and aluminium powder clay pot

TN

sand bucket

Equipment 

iron oxide

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dry sand

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aluminium powder

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barium peroxide and magnesium powder ‘starter’

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large crucible or small plant pot

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long fuse of magnesium ribbon

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bucket

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Bunsen burner and spill or small gas blow lamp

Note: the iron oxide and aluminium powder must be very well mixed. The fuse needs to be long enough to give the teacher the opportunity to stand well back.

1 Set up the apparatus behind tall safety screens. It is wise to practise carrying out the reaction beforehand. 2 Alternatively, the reaction can be carried out outside with all the pupils standing well back (3–4 metres) and wearing eye protection. 3 To initiate the reaction make a hole in the thermit mixture, gently pour in the ‘starter’ and insert the magnesium ribbon fuse. 4 Light the magnesium fuse using a spill. Alternatively, the magnesium fuse can be lit using a hand-held Bunsen burner (great care!) or a butane blowlamp. 5 Stand well back! The reaction is very spectacular with lots of flames and sparks. 6 Show pupils the photograph of the reaction in use on the railways. 7 Draw attention to the word equation. The iron produced is molten at the very high temperature of the reaction and seals the two rails together Equation iron oxide +aluminium → aluminium oxide +iron

8 Highlight the importance of this reaction to the development of the railways.

Safety note All present need eye protection. If done outside a calm windless day is essential. Staff who have not done this before require practice in the procedure under the supervision of an experienced member of the science department. The procedure must be very closely followed. Tried and tested variations appear in a number of ASE and CLEAPSS publications. No others shoul d be used.


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Variables together – Think about

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UG LP

Bridging to the unit

Setting the context

Concrete preparation

Display of corroded objects to link to previous lessons.

Show car adverts and discuss why it is important to understand rusting.

Using a bike as an example, pupils make a list of factors that may affect whether or not iron rusts.

Bridging to the unit 

Show pupils a display of heavil y corroded objects.

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Ask them questions to check their understanding of corrosion.

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Write the word equation for rusting on the board.

Equipment heavily corroded objects, e.g. old nails, bolts, etc. Questions 1 What is needed for iron to go rusty? 2 What does the iron react with? 3 What is the chemical name for rust? 4 What conditions make iron rust faster?

Setting the context 

Show car adverts either from magazines or as recorded clips from TV. Stress that car manufacturing is a huge business and that rusting causes car bodywork to be less safe and engines to break down. Stress that no other metal can replace iron due to costs.

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Understanding the rusting process has enabled better corrosion prevention techniques to be used. Car manufacturers now give 5 year anti-corrosion warranties.

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Ask pupils to suggest ways that cars are protected from rusting (e.g. painting, oiling, sealing undercarriages, use of plastics and alloys for smaller components).

Answers 1 oxygen and water; 2 oxygen; 3 iron oxide; 4 acidic, salt, etc.

Concrete preparation 

Either look at a bike and ask pupils to think about why bike parts go rusty and to list how iron is prevented from rusting.

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Or ask pupils to think about cars and bikes and make a list of ways that iron is prevented from rusting.

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Focus on conditions of rusting, e.g. wet bikes, and how bike parts are protected, e.g. plastic coatings, greased chains, alloys, paint/varnish.

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List pupils’ ideas on the board and use them to decide what factors affect iron rusting.


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Reactive metals and oxygen

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Teacher activity notes

Type

Purpose

Differentiation

Practical

Demonstration to show pupils that metals react at diff erent rates with oxygen in the air to form metal oxides.

Core No pupil sheets

Running the activity

Show pupils jars containing sodium and either lithium or potassium stored under oil. Point out that these metals are so reactive that they are stored in dark bottles under oil to exclude UG LP air and light. TC

Demonstrate the reaction of each metal with air as follows.

1 Remove a piece of the metal from the oil using forceps and place on a ceramic tile. The oil can be removed, if necessary, using a tissue. 2 Cut the metal using a scalpel to reveal a shiny surface. 3 Ask pupils to watch as the surface quickly becomes dull as the metal tarnishes. This can be seen more clearly using a digital mi croscope linked to a light projector, if available. 4 Discuss the reaction between the metal and oxygen and write a word equation on the board to show a metal oxide is formed. Tell pupils that many (but not all) other metals react with oxygen but the reactions are much slower. More able pupils may notice that the rate of tarnishing varies between the metals they see. Show pupils samples of shiny and heavily corroded iron. Draw attention to the fact that the reaction is similar, but too slow to be seen happening. For your information: lithium +oxygen → lithium oxide 4Li +O2 → 2Li 2O sodium +oxygen → sodium oxide 4Na +O2 → 2Na2O potassium +oxygen → potassium oxide 4K +O2 → 2K 2O iron +oxygen → iron oxide 2Fe +3O2 → 2FeO 3

Expected outcomes All metals tarnish very quickly in air. Potassium reacts fastest, then sodium and lithium slowest of all (there is no need to show pupils all three). This is related to the relative reactivity of the metals, which increases down group I of the periodic table.

Safety notes Eye protection should be worn. The reactive metals should be stored in a secure place out of the reach of the pupils until needed, and returned to safe storage immediately after the demonstration.

ICT opportunities Use of a digital mi croscope and light projector. Pupils search the Internet for reactions of metals with oxygen. Relevant sites include: WebElements Periodic Table RSC’s chemical science network: visual interpretation of the Table of Elements


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Reactive metals and oxygen

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Technician activity notes

Type

Purpose

Differentiation

Practical

Demonstration to to sh show pupils th that me metals re react at at di different ra rates wi with ox oxygen in the air to form metal oxides.

Core No pupil sheets

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Equipment needed

UG LP

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TN

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small piece of sodium and either lithium or potassium stored under oil samples of heavily corroded iron e.g. nails and bolts

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white whi te tile til e, sc scalpe alpel, l, forceps forceps

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(optional) digital microscope and light projector

For your information Running the activity Show pupils jars containing sodium and either lithium or potassium stored under oil. Point out that these metals are so reactive that they are stored in dark bottles under oil to exclude air and light. Demonstrate the reaction of each metal with air as follows.

1 Remove a piece of the metal from the oil using forceps and place on a ceramic tile. The oil can be removed, if necessary, using a tissue. 2 Cut the metal using a scalpel to reveal a shiny surface. 3 Ask pupils to watch as the surface quickly becomes dull as the metal tarnishes. This can be seen more clearly using a digital microscope linked to a light projector, if available. 4 Discuss the reaction between the metal and oxygen and write a word equation on the board to show a metal oxide is formed. Te Tell pupils that that ma many (bu (butt not not all) all) othe otherr me metals tals rea react with oxy oxyg gen but but the the rea reactions ctions are much much slowe slowerr. More able pupils may notice that the rate of tarnishing varies between the metals they see. Show pupils samples of shiny and heavily corroded iron. Draw attention to the fact that the reaction is similar, but too slow to be seen happening. For your information: lithium +oxygen → lithium lithi um oxide oxide 4Li +O2 → 2Li 2O sodium odi um +oxyge + oxygen n → sodium oxide oxi de 4Na +O2 → 2Na2O potassium +oxygen → potass potassium iu m oxide ox ide 4K +O2 → 2K 2O iron +oxygen +oxygen → iron oxide 2Fe +3O2 → 2FeO 3

Expected outcomes All Al l metals metals tarn tarnish ish very quickly qui ckly in i n ai r. Potas Potassium iu m reacts reacts faste fastes st, the th en sodium odi um and l ithi it hium um slowest slowest of all (there i s no ne n eed to show pupils pupi ls all thre thr ee). Thi Th i s is relate related d to the th e relative relative rea reactivity ctivi ty of the metals metals,, which wh ich i ncreas ncreases down group I of the periodic table. Safety notes Eye protection should be worn. The rea reactive ctive meta metals ls should be store tored in a secure place place out of the rea reach of the pupils pupils until nee needed, ded, and returned to safe storage immediately after the demonstration.

ICT opportunities U se of a digital mi croscope croscope and light li ght proj ector. ctor. Pupils Pupi ls sea search the th e Inte In ternet rnet for rea reactions ction s of metals metals with wi th oxygen. oxygen. Relevant sites include: WebElements Periodic Table RSC’s chemical science network: visual interpretation of the Table of Elements © Harcourt Education Education Ltd 2004 Catalyst 3 This This work workshee heet ma may hav have bee been alte altered red fro from m the the orig origin ina al on the the CD-R CD-ROM.

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Tarnished metal


Type

Purpose

Differentiation

Paper

Pupils answer qu questions about gold, iron an and chromium corroding under di different conditions.

Core


Pupils work independently or in small groups to answer the questions on the worksheets. Less able pupils may need support to help them think about what UG LP conditions apply to each diagram, e.g. ‘wet’ ‘dry’ ‘no air’ etc.

ICT opportunities Pupils could search the Internet for ‘Stainless steel composition’. Stainless steel is made from chromium added to iron. The chromium stops the iron from rusting rustin g so so tha th at it i t can be use used for fo r surgical surgical instrume i nstruments, nts, ‘hypoall ‘h ypoalle ergeni rgenic’ c’ jewe jewelle llery ry and cutle cutlery ry.. Alloying Alloying is more more efficient fficient tha than n plating plating beca becaus use e the plating is prone to flaking off.

Answers 1 1 Dry, plenty of air, hot. 2 Cold, no air, wet. 3 Warm, wet, plenty of air. 4 Warm, wet, plenty of air. 5 Cold, wet, plenty of air. 2 Box 5 shows that chromium does not corrode when it is wet. Box 3 shows that iron corrodes quickly when it is wet. (Note that both pieces of information in formation are neede needed.) d.) 3 Iron does not rust in diagram 1 because there is no water. In diagram 2 there is no air. Iron rusts quickly in diagram 3 because there is air and water (and it is warm).

© Harcourt Education Education Ltd 2004 Catalyst 3 This This work workshee heet ma may hav have bee been alte altered red fro from m the the orig origin ina al on the the CD-R CD-ROM.

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Tarnished metal

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Metals tarnish when they react with oxygen in the air.

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These diagrams show how different metals tarnish (go dull) and corrode under different conditions. conditions.

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1

Archaeologists have found gold and iron objects buried in the dry sands of the Egyptian desert. They look new even though they are thousands of years old.

2

A Viking knife made of iron was found buried under wet, airtight clay. It was only a little rusty after being buried for over a thousand years.

3

Iron door hinges in a warm, wet bathroom go very rusty after only a few weeks.

4

Gold rings stay shiny for years, even though people wear them all the time.

5

Old car bumpers used to be plated with chromium . This metal stays shiny even when it keeps getting wet.

UG LP TN

1

2

3

Activity Core

Describe the conditions in each diagram, for example, ‘very wet with lots of air’. What information shows that iron is more reactive than chromium? Explain why the iron objects have corroded at different rates.


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Inside the atom

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Type

Purpose

Differentiation

Paper

To stretch the most able pupils, by dealing with the concept of atomic structure.

Extension


A pupil capable of dealing with the concept of atomic structure should be capable of working through this sheet alone. However, with a very able class, the teacher may wish to talk about atomic structure and then give pupils the sheet to complete in class or for UG LP homework. ^

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Expected outcomes Completed questions showing understanding of the concept.

Pitfalls Atomic structure is a KS4 topic and should only be broached with pupils who are comfortable with using scientific models and with formal scientific thinking. Each school should consider whether they wish to broach this KS4 concept during the KS3 course.

Answers 1 11 protons 2 11 electrons 3 a 2 electrons b 8 electrons c 1 electron 4 (Possible answer) In a cell. They are both in the middle.

5 –11 ++11 =0 6 a 6 protons b 6 electrons c


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Inside the atom

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UG LP TN

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Activity Extension

You are going to learn about a model that scientists use to describe what is inside the atom. Atoms have a central part called the nucleus. The nucleus contains the protons. Whizzing around the nucleus are the electrons . The electrons are grouped together. The group closest to the nucleus is said to make up the ‘inner shell’, and the second closest group makes up the ‘second shell’. An atom can have up to seven ‘shells’. The sodium atom in the diagram has three shells, represented by the three circles around the central nucleus. 1 2 3

4

proton

How many protons are in the sodium atom? How many electrons are in the sodium atom? How many electrons are in: a the inner shell b the next shell c the outer shell?

electron

Where else have you heard the word ‘nucleus’? What is similar about the atom’s nucleus and the other nucleus?

The shells are filled up in order from the inside. The inner shell can take two electrons and the second shell takes eight electrons. Sodium has one more electron, which is in the outer shell. You may remember electrons from when you studied electricity. Electrons move along the wires, carrying the energy. If you made a wire out of sodium (difficult and dangerous, but not impossible) it would be the electron from the outer shell that moved between atoms, carrying the energy. Protons and electrons are charged and charge comes in both negative and positive amounts. Electrons have a charge of –1 each. Protons have a charge of +1 each. 5

Add up all the charges in the sodium atom.

Atoms in an element contain the same number of protons as electrons. This means that the overall charge of an atom in an element is zero. The number of protons in an atom is called the atomic number. For the atoms in an element, the atomic number also gives the number of electrons, because the number of protons equals the number of electrons. 6

Carbon has atomic number 6. a How many protons does it have? b How many electrons does it have? c Look at the diagram for the sodium atom. Draw a similar diagram for a carbon atom.


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Reacting metals with water

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UG LP


Type

Purpose

Differentiation

Practical

Demonstration to show pupils that very reactive metals react very quickly with water to produce a metal hydroxide and hydrogen.

Core

Running the activity Before carrying out the demonstration, ask pupils to copy the results table so that they can complete it during the demonstration. The table could be enlarged and photocopied for less able pupils.

TC

forceps small piece of metal

water and universal indicator Demonstrate the reaction of sodium with water as shown in the diagram. The sodium can be cut using forceps and a scalpel, on a ceramic tile. The piece should be wiped with a tissue to remove any oil. Add enough universal indicator solution to give a distinct green colour to the water before starting. Draw pupils’ attention to the observations that the sodium floats and fizzes (implying a gas is made) and that the universal indicator goes blue due to the formation of an alkali (sodium hydroxide). Write a word equation on the board. Sodium +water → sodium hydroxide +hydrogen

lighted spill

bung

calcium water

Repeat the demonstration using potassium and then calcium (it is easiest to use three separate troughs). Carry out the calcium experiment again, this time using a rice-grain sized piece in a test tube. Let the gas build up using a bung, and show pupils that the gas pops when a lighted splint is brought near, proving that the gas is hydrogen. This can be used as a demonstration to remind pupils how to test for hydrogen in preparation for Activity F2b. Ask a pupil to feel the test tube after the reaction has finished – it feels warm due to energy being given out during the reaction. If not already shown as a starter, Catalyst Interactive Presentations 3 shows the reaction of more reactive metals, rubidium and caesium, with water. These reactions can be shown and pupils make further observations to add to their tables.


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Reacting metals with water (continued)


Other relevant material

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Skill sheet 15: Word equations

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Expected outcomes

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Potassium reacts most vigorously, producing a flame of burning hydrogen. The universal indicator goes blue as the hydroxide is formed. Sodium reacts similarly, but not as vigorously, calcium slowest of all.

UG LP TC

Safety notes Always use a large trough of cold water. Never try to contain the sodium or potassium on the surface of the water – let it run free. All present should wear eye protection, and use a safety screen. Do not allow reactive metals to come into contact with skin.

ICT opportunities Pupils can see the reactions by going to the following website: RSC’s chemical science network: visual interpretation of the Table of Elements

Answers 1 a Potassium (or caesium if video is shown). b (Caesium, rubidium), potassium, sodium, calcium. 2 1 Reaction is faster than with sodium. 2 Universal indicator goes blue. 3 Fizzing seen, lighted spill goes pop. 4 Flames seen for potassium, calcium makes the test-tube warm. 5 Sodium floats.

3 sodium +water → sodium hydroxide +hydrogen calcium +water → calcium hydroxide +hydrogen potassium +water → potassium hydroxide +hydrogen


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F2a M

Type

Purpose

Differentiation

Practical

Demonstration to show pupils that very reactive metals react very quickly with water to produce a metal hydroxide and hydrogen

Core

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UG LP

Equipment  

TN


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troughs of water (3 if possible) sodium, potassium and calcium pieces forceps, scalpel, white tile, tissues

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universal indicator solution Bunsen burner and spills test tube, rack and bung

Other relevant material Skill sheet 15: Word equations

For your information Running the activity Before carrying out the demonstration, ask pupils to copy the results table so that they can complete it during the demonstration. The table could be enlarged and photocopied for less able pupils. Demonstrate the reaction of sodium with water as shown in the diagram. The sodium can be cut using forceps and a scalpel, on a ceramic tile. The piece should be wiped with a tissue to remove any oil. Add enough universal indicator solution to give a distinct green colour to the water before starting. Draw pupils’ attention to the observations that the sodium floats and fizzes (implying a gas is made) and that the universal indicator goes blue due to the formation of an alkali (sodium hydroxide). Write a word equation on the board.

forceps small piece of metal

water and universal indicator

sodium +water → sodium hydroxide +hydrogen Repeat the demonstration using potassium and then calcium (it is easiest to use three separate troughs). Carry out the calcium experiment again, this time using a rice-grain sized piece in a test tube. Let the gas build up using a bung, and show pupils that the gas pops when a lighted splint is brought near, proving that the gas is hydrogen. This can be used as a demonstration to remind pupils how to test for hydrogen in preparation for Activity F2b. Ask a pupil to feel the test tube after the reaction has finished – it feels warm due to energy being given out during the reaction. If not already shown as a starter, Catalyst Interactive Presentations 3 shows the reaction of more reactive metals, rubidium and caesium, with water. These reactions can be shown and pupils make further observations.

lighted spill

bung

calcium water

Expected outcomes Potassium reacts most vigorously, producing a flame of burning hydrogen. The universal indicator goes blue as the hydroxide is formed. Sodium reacts similarly, but not as vigorously, calcium slowest of all.

Safety notes Always use a large trough of cold water. Never try to contain the sodium or potassium on the surface of the water – let it run free. All present should wear eye protection, and use a safety screen. Do not allow reactive metals to come into contact with skin. ICT opportunities Pupils can see the reactions by going to the following website: RSC’s chemical science network: visual interpretation of the Table of Elements ©Harcourt Education Ltd 2004 Catalyst 3 This worksheet may have been altered from the original on the CD-ROM.

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Activity Core

Many metals react with water. Some, like iron, react too slowly to see any change happen. Others react so quickly that the ? change can be seen in a few seconds. You are going to watch u your teacher demonstrate how some reactive metals react with water. You need to write down what you see happening.

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Wear eye protection. Watch the reactions through the safety screen.

UG LP

forceps TN TC

small piece of metal

water and universal indicator

Obtaining evidence 1

Make a larger copy of this table.

Metal

Observations

sodium potassium calcium 2

Write down your observations as your teacher carries out the demonstration.

Considering the evidence 1

a b

2

Decide which metal is most reactive. Make a list of the metals in order, ‘most reactive’ to ‘least reactive’.

Eve watched the demonstration and wrote down these conclusions in her exercise book:

1. 2. 3. 4. 5.

Potassium is a more reactive metal than sodium. An alkali is made when the metals react with water. When metals react with water, hydrogen gas is made. Energy is given out during the reactions. Sodium is less dense than water.

What evidence did you see to support each of Eve’s statements? 3

The general equation for the reaction is metal +water → metal hydroxide +hydrogen Write word equations to show what happens for each reaction you saw.


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Reacting metals with acids


Type

Purpose

Differentiation

Practical

Pupils carry out an experiment to react metals with dilute hydrochloric acid.

Core (Extension), Help

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Show pupils the technique of testing for hydrogen. This can be done by emphasising the technique during the demonstration of the reaction between calcium and water in Activity F2a.

UG LP TC

Ask pupils to design their tables for recording observations before starting the practical. Emphasise the outcome that copper does not react with dilute acids.

Core: Follow instructions on Activity sheet F2b. Help: This has a table to record observations and simplified questions. Extension: Additional questions are available at the bottom of the core sheet.

Other relevant material Skill sheet 33: More word equations

Expected outcomes Core: Magnesium reacts quickly with dilute acid and produces enough hydrogen to give a definite ‘pop’. Zinc fizzes less vigorously, iron produces bubbles slowly. Help: As core, with less emphasis on Sc1. Extension: Pupils have the opportunity of practising planning and predicting skills for Sc1.

Pitfalls The QCA Scheme of Work recommends that the acids used are at concentrations of 0.4 mol/dm3. This is lower than was traditionally used for these experiments. The reactions of iron and zinc are slow at this concentration. The hydrogen ‘pop’ test is unlikely to work satisfactorily because only small quantities of hydrogen are evolved. Pupils need to look carefully to compare the rate of bubbles of hydrogen evolved.

Safety notes Wear eye protection. Wash any acid splashes off skin immediately.

Answers Core: 1 Magnesium, zinc, iron, copper. 2 Potassium, sodium, calcium, magnesium, zinc, iron, copper, gold. 3 zinc +hydrochloric acid → zinc chloride +hydrogen iron +hydrochloric acid → iron chloride +hydrogen Help: 1 Sodium, magnesium, zinc, iron, copper, gold. 2 zinc +hydrochloric acid → zinc chloride +hydrogen iron +hydrochloric acid → iron chloride +hydrogen Extension: 4 zinc +sulphuric acid → zinc sulphate +hydrogen iron +sulphuric acid → iron sulphate +hydrogen 5 a magnesium b Same volume of dilute acid; weighed samples of all four metals; measure temperature change during reactions; magnesium should be greatest.


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Purpose

Differentiation

Practical

Pupils carry out an experiment to react metals with dilute hydrochloric acid.

Core (Extension), Help

Equipment For each group: 

UG LP


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four test tubes, bungs and rack 0.4 mol/dm3 hydrochloric acid metals: iron filings, magnesium ribbon, small pieces of granulated zinc, copper turnings spatulas Bunsen burner and spills


For your information Running the activity Show pupils the technique of testing for hydrogen. This can be done by emphasising the technique during the demonstration of the reaction between calcium and water in Activity F2a. Ask pupils to design their tables for recording observations before starting the practical. Emphasise the outcome that copper does not react with dilute acids.

Core: Follow instructions on Activity sheet F2b. Help: This has a table to record observations and simplified questions. Extension: Additional questions are available at the bottom of the core sheet. Expected outcomes Core: Magnesium reacts quickly with dilute acid and produces enough hydrogen to give a definite ‘pop’. Zinc fizzes less vigorously, iron produces bubbles slowly. Help: As core, with less emphasis on Sc1. Extension: Pupils have the opportunity of practising planning and predicting skills for Sc1. Pitfalls The QCA Scheme of Work recommends that the acids used are at concentrations of 0.4 mol/dm3. This is lower than was traditionally used for these experiments. The reactions of iron and zinc are slow at this concentration. The hydrogen ‘pop’ test is unlikely to work satisfactorily because only small quantities of hydrogen are evolved. Pupils need to look carefully to compare the rate of bubbles of hydrogen evolved.

Safety notes Wear eye protection. Wash any acid splashes off skin immediately.


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Activity Core

Many metals react with acids. In this experiment you are going to look at how quickly four different metals react with dilute hydrochloric acid.

Wear eye protection. Take care when handling acid. Wash any acid splashes with lots of water.

Obtaining evidence 1

2

3

4

5

6

Design a table to present your observations. Add 2 cm depth of acid to four test tubes in a test tube rack. Set up a lighted Bunsen burner and have a bung and spill ready to test for hydrogen. Add a small piece of magnesium to the first test tube. Record the observations you see. Test the gas to see if it is hydrogen. Investigate zinc, iron and copper in the same way.

Hydrogen pops when lit.

bung lighted spill

hydrochloric acid magnesium

Considering the evidence 1 2

3

Put the four metals in order from ‘most reactive’ to ‘least reactive’. Write a full list of reactivity to include these metals: sodium, gold, calcium, magnesium, potassium, iron, copper and zinc. The general equation for reacting metals with hydrochloric acid is metal +hydrochloric acid → metal chloride +hydrogen Write word equations for the reactions of zinc and iron with hydrochloric acid.

Extension 4

Sulphuric acid reacts with metals to make a metal sulphate and hydrogen. Write word equations for zinc and iron reacting with sulphuric acid.

5

a

b

Predict which of the four metals (magnesium, zinc, iron, copper) gives out most energy when it reacts with acid. Explain your reasoning. Give an outline of an experiment that would show whether your prediction is right.


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Use this sheet to record your observations.

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Activity Help

Use this table to record what you see.

Metal

Observations

Did the gas go pop?

magnesium copper zinc iron


Put these metals in order ‘most reactive’ to ‘least reactive’. copper

2

magnesium

iron

zinc

gold

sodium

This is the equation for magnesium reacting with hydrochloric acid. magnesium +hydrochloric acid → magnesium chloride +hydrogen

Complete the equations for zinc and iron. zinc +hydrochloric acid →

+

iron +hydrochloric acid →

+


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Relatively reactive

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Differentiation

ICT

Pupils use a database to work out a reactivity series of metals.

Core, Help, Extension


Pupils allocate a ‘reactivity rating’ for the 24 common metals in the database, according to the questions in the database that relate to reactivity (see Activity sheets). The teacher can modify the database as required (e.g. the last column hidden UG LP for Core and Help, or use the sort function to hide the non-metals for Help). ^

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Core: There are three questions to apply to the database, giving a rating of 1 (most reactive) to 4 (least reactive). Pupils should use the ‘Sort’ function to organise the metals into the categories. Help: Pupils fill in their answers on the sheet, which shows them how many metals belong in each category. Extension: There are four questions to apply to the database, the extra question introduces the idea that carbon has its place in the reactivity series. Pupils rate the common metals on a scale of 1–5, deciding for themselves what combination of answers defines each category. This PC-based activity uses a Microsoft® Excel spreadsheet available on the CD-ROM that accompanies this pack.

Other relevant material Skill sheet 26: Designing a spreadsheet

Expected outcomes Pupils use data stored in the database to categorise metals according to their reactivity.

Pitfalls Make sure the pupils have selected the most common metals. You may like to show them how to split the screen, or how to hide columns, so that they can see which metal goes with which combination of answers. With less IT literate pupils, you could hide the irrelevant columns in advance, or adapt the spreadsheet to show only metals.

Answers Core: 1 1: Lithium, sodium, potassium, rubidium, caesium, strontium, barium. 2: Beryllium, magnesium, calcium. 3: Aluminium, tin, lead, chromium, manganese, iron, nickel, cobalt, zinc. 4: Copper, sil ver, platinum, gold, mercury. Help: 1 See Core 1 above. Extension: 1 1 =lithium, sodium, potassium, rubidium, caesium, strontium, barium. 2 =beryllium, magnesium, calcium. 3 =aluminium. 4 =tin, lead, chromium, manganese, iron, nickel, cobalt, zinc. 5 =copper, silver, platinum, gold, mercury. 2 The more reactive metals are in group I and group II. ©Harcourt Education Ltd 2004 Catalyst 3 This worksheet may have been altered from the original on the CD-ROM.

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Relatively reactive reactive

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Activity Core

You are going to give 24 common metals a ‘reactivity rating’ on a 1 to 4 scale, where 1 is most reactive and 4 is least reactive. You You are goin going g to to us use a data databa bas se. You You are only only to wor work on comm ommon metals tals,, so use a filter to select the common metals. There are three questions that relate to reactivity. The answers to these questions are used to decide the rating.

UG LP TN

Reactivity rating

Does it have to be stored under der oil oil or in an inert gas?

Does it react in col cold water within five minutes?

Does it react with dilute hydrochlori oric acid within five minutes?

1

yes

yes

yes

2

no

yes

yes

3

no

no

yes

4

no

no

no

1

Put each of the 24 common metals into one of the four categories.


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You are going to give 24 common metals a ‘reactivity rating’ on a 1 to 4 scale, where 1 is most reactive and 4 is least reactive. You You are goin going g to to us use a data databa bas se. You You are only only to wor work on comm ommon metals tals,, so use a filter to select the common metals. There are three questions that relate to reactivity. The answers to these questions are used to decide the rating.

Reactivity rating

Does it have to be stored under der oil oil or in an inert gas?

Does it react in col cold water within five minutes?

Does it react with dilute hydrochlori oric acid within five minutes?

1

yes

yes

yes

2

no

yes

yes

3

no

no

yes

4

no

no

no

1

Put each of the 24 common metals into one of the four categories.


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Activity Help

You are going to give 24 common metals a score to show how reactive they are. A score of 1 is the most reactive. A score of 4 is the least reactive.

UG LP

You You are goin going g to to us use a data databa bas se. You You are only only to wor work on comm ommon metals tals..

TN

The There are thr three que question tions s tha that re relate late to reactiv tivity ity. The The answer wers to the these que question tions s are used to decide the score.

Score

Does it have to be stored under oil or in an inert gas?

Does it react in cold water within five minutes?

Does it react with dilute hydrochloric acid within five minutes?

1

yes

yes

yes

2

no

yes

yes

3

no

no

yes

4

no

no

no

1 2

1

Select the metals which have ‘yes’ in the ‘Is it a common metal?’ metal?’ column. Use the filters to pick out the metals with each score. Use the table above to help you. Record your answers by writing the names of the metals in this score chart:

Score

1

2

3

4

Metals with this score


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Activity Extension


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You are going to decide on the relative reactivity of 24 common metals. You You are goin going g to to us use a data databa bas se. You You are only only to wor work on common metals. The database contains the answers to four questions about reactivity. One of the questions mentions carbon. Even though carbon is not a metal, metal, it is is us useful eful to place place it in in the the reactivity reactivity series series.. M etals etals below carbon in the series can be extracted from their compounds by reaction with carbon. Some metals cannot be extracted from their compounds by carbon. These metals are above carbon in the reactivity series.

Question

Relatively Relatively more more reac reacti tive ve less less reac reacti tive ve

Does it have to be stored under oil or in an inert gas?

yes

no

Does it react in cold water within five minutes?

yes

no

Does it react with dilute hydrochloric acid within five minutes?

yes

no

Could it be made from its compounds using carbon?

no

yes

1

2

Use the database to allocate each of the common metals to one of five categories, where category 1 contains the most reactive metals and category 5 contains the least reactive metals. Look at a periodic table while thinking about your five categories. Do you see any pattern?


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Electrons in atoms

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Type

Purpose

Differentiation

Paper

To cater for the interest in atoms that some, usually more able, pupils express in Year 9. This activity encourages the pupil to make the link between the periodic table and the arrangement of electrons in atoms.

Extension


Although the link between the periodic table and the arrangement of electrons in atoms is UG LP considered a KS4 topic, it (along with Activities F1c and F3c ) will allow access to part of the attainment target for EP in Sc3: ‘Recognising that differences in the properties of materials relate to the nature of the particles within them’. The activity is designed to be done by a pupil or a pair of pupils working alone, so more assistance is provided than is usual for an Extension activity. Pupils can either work on the sheet itself or on an enlarged photocopy of the diagram. Alternatively they can draw the atoms on a separate piece of paper. Full answers are provided below, so that pupils can mark their own work.

Expected outcomes Pupils should be able to recognise the patterns in electron arrangement and use this insight to answer questions 4 and 5.

Pitfalls Atomic structure is a not a suitable topic for the great majority of Year 9 pupils, who need to concentrate on the KS3 curriculum.

Answers 1, 2

0

1 2 H I

II

III

IV

V

VI

VII

3

4

5

6

7

8

9

He 10

Li 11

B 12

Be 13

C 14

N 15

O 16

F 17

Ne 18

Al

Si

P

S

Cl

Ar

Na

Mg

19

20

K

Ca

3 The number of electrons in the outer shell equals the group number for groups I–VI I. 4 All their electron shells are full, even the outer one. 5 a Hydrogen has one electron in its outer shell and therefore belongs in group I. b Hydrogen has one electron missing in its outer shell, and therefore belongs in group VII with the other elements that have one electron missing in their outer shells. ©Harcourt Education Ltd 2004 Catalyst 3 This worksheet may have been altered from the original on the CD-ROM.

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Electrons in atoms

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You are going to work out the electron arrangement of the first 20 elements in the periodic table. The rules for arranging electrons are as follows: 



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Activity Extension





The atomic number gives the number of protons and therefore the number of electrons. Fill the ‘shells’ from the inside outwards. The inner shell can take up to two electrons. The second and third shells take up to eight electrons.

Remember: In any element, the number of protons equals the number of electrons. 1

Fill in the electrons for the first 10 elements. Two are done for you, so that you can check you are doing it correctly. 1 2

2

3

4

5

H Group I 3

4

5

6

7

8

9

He 10

Li 11

Be 12

B 13

C 14

N 15

O 16

F 17

Ne 18

Na 19

Mg 20

Al

Si

P

S

Cl

Ar

K

Ca

Group I has been labelled on the diagram above. Label the other groups: II, III, IV, V, VI, VII and 0. Look at groups I to VII. Describe the relationship between the number of electrons in the outer shell and the group number. Look at group 0. What do the atoms of the three elements in group 0 (helium, neon and argon) have in common? In this version of the periodic table, hydrogen has been put in group I. However, some versions of the periodic table put hydrogen in group VII. a

b

Give one reason, based on its arrangement of electrons, why hydrogen should be in group I. Give one reason, based on its arrangement of electrons, why hydrogen should be in group VII.


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Displacement reactions

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Type

Purpose

Differentiation

Practical

Pupils use test tube displacement reactions to investigate reactivity of three metals

Core, Help

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Pupils follow the Activity sheet. They establish whether copper or zinc is more reactive, before comparing magnesium to copper and zinc to copper.

UG LP

Core: Pupils follow the instructions on the sheet and draw up their own table of results.

TC

Help: The teacher shows pupils what to do, then they record their results and complete the equations on the Activity sheet.


Expected outcomes Zinc displaces copper from copper sulphate solution. Brown copper will be seen; the blue solution of copper sulphate will get paler and the test tube will become warm. There is no reaction between copper and zinc sulphate solution. Magnesium displaces copper from copper sulphate solution. Brown copper will be seen, the blue solution of copper sulphate will get paler and the test tube will become warm. There is no reaction between copper and magnesium sulphate solution. Magnesium displaces zinc from zinc sulphate solution. There are no colour changes to be seen, but the test tube will become warm. There is no reaction between zinc and magnesium sulphate solution.

Pitfalls Pupils find displacement reactions very confusing and will need support to understand what they see.

Safety notes Eye protection should be worn at all times. Any splashes should be immediately rinsed.

Answers Core:

Help:

1 Zinc +copper sulphate, magnesium +copper sulphate, magnesium +zinc sulphate. Colour changes and/or warming show this. 2 no 3 yes 4 zinc 5 Zinc +copper sulphate → copper +zinc sulphate 6 magnesium 7 Magnesium +copper sulphate → magnesium sulphate +copper 8 magnesium 9 Magnesium +zinc sulphate → magnesium sulphate +zinc 1 2 3 4 5 6

zinc Zinc +copper sulphate → copper +zinc sulphate Magnesium Magnesium +copper sulphate → magnesium sulphate +copper magnesium Magnesium +zinc sulphate → magnesium sulphate +zinc


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Practical

Pupils use test tube displacement reactions to investigate reactivity of three metals.

Core, Help


UG LP TN




6 test tubes test tube rack

For the class: 



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4 ×250 cm3 0.5 mol/dm3 copper(II) sulphate solution, with labelled small beaker and graduated plastic dropping pipette 4 ×250 cm3 0.5 mol/dm3 magnesium sulphate solution, with labelled small beaker and graduated plastic dropping pipette 4 ×250 cm3 0.5 mol/dm3 zinc sulphate solution, with labelled small beaker and graduated plastic dropping pipette



4 small pots of copper turnings, with spatula



4 small pots of magnesium turnings, with spatula



4 small pots of zinc turnings, with spatula


For your information Running the activity Pupils follow the Activity sheet. They establish whether copper or zinc is more reactive, before comparing magnesium to copper and zinc to copper. Core: Pupils follow the instructions on the sheet and draw up their own table of results. Help: The teacher shows pupils what to do, then they record their results and complete the equations on the Activity sheet. Expected outcomes Zinc displaces copper from copper sulphate solution. Brown copper will be seen; the blue solution of copper sulphate will get paler and the test tube will become warm. There is no reaction between copper and zinc sulphate solution. Magnesium displaces copper from copper sulphate solution. Brown copper wil l be seen, the blue solution of copper sulphate will get paler and the test tube will become warm. There is no reaction between copper and magnesium sulphate solution. Magnesium displaces zinc from zinc sulphate solution. There are no colour changes to be seen, but the test tube will become warm. There is no reaction between zinc and magnesium sulphate solution.

Pitfalls Pupils find displacement reactions very confusing and will need support to understand what they see. Safety notes Eye protection should be worn at all times. Any splashes should be immediately rinsed. ©Harcourt Education Ltd 2004 Catalyst 3 This worksheet may have been altered from the original on the CD-ROM.

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You are going to carry out some displacement reactions to decide which metal is more reactive. You are going to use ‘turnings’, which are small, curved pieces of metal. Remember – In a displacement reaction, the more reactive metal displaces the less reactive metal from its compound.

Activity Core

Wear eye protection. Wash any splashes of solutions off your skin immediately.

Obtaining evidence You are going to try reacting zinc with copper sulphate solution, then copper with zinc sulphate solution. 1 2

3 4 5 6 7

8 9

10 11

Draw up a table to record your observations. Put about 2 cm3 of copper sulphate solution in a test tube. Add 1 small spatula of zinc turnings. Write down your observations in your table. Put about 2 cm3 of zinc sulphate solution in another test tube. Add 1 small spatula of copper turnings. Write down your observations in your table. Now you are going to try reacting magnesium with copper sulphate solution, then copper with magnesium sulphate solution. Draw up a table to record your results. Carry out the tests as you did in steps 2 to 7 above. Finally you are going to try reacting first zinc with magnesium sulphate solution, then magnesium with zinc sulphate solution. Draw up a table to record your results. Carry out the tests as you did in steps 2 to 7 above.

copper sulphate zinc turnings


2 3 4 5 6 7 8 9

In which test tubes did a chemical reaction take place? How did you know? Did copper displace zinc from the zinc sulphate? Did zinc displace copper from the copper sulphate? Which is the more reactive metal, zinc or copper? Write a word equation for the reaction that happened. Which is the more reactive metal, copper or magnesium? Write a word equation for the reaction that showed this. Which is the more reactive metal, zinc or magnesium? Write a word equation for the reaction that showed this.


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Activity Help

You are going to carry out some displacement reactions to decide which metal is more reactive. You are going to use ‘turnings’, which are small, curved pieces of metal. Your teacher will show you what to do. Record your observations and fill in the answers below. Remember – In a displacement reaction, the more reactive metal displaces the less reactive metal from its compound.

Reactants

Observations

Which metal displaced which?

zinc and copper zinc copper sulphate solution copper zinc sulphate solution

magnesium and copper magnesium copper sulphate solution copper magnesium sulphate solution

zinc and magnesium zinc magnesium sulphate solution magnesium zinc sulphate solution 1

Which is the more reactive metal, zinc or copper?

2

Complete this word equation: zinc +copper sulphate →

3

Which is the more reactive metal, magnesium or copper?

4

Complete this word equation: magnesium +copper sulphate →

5

Which is the more reactive metal, zinc or magnesium?

6

Complete this word equation: magnesium +zinc sulphate →


+

+

+

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Displacement in action


Type

Purpose

Differentiation

Practical

Pupils look at zinc displacing copper and consider other applications of displacement.

Core

Running the activity Pupils set up the experiment as shown on Activity sheet F3b.

Pupils work in groups to explain their ideas about what is happening. They need to link UG LP their observations of copper plating the zinc strip to the idea that zinc is more reactive than copper. More able pupils may be encouraged to think about what would happen to TC the colour of the copper sulphate solution over time. Pupils should then consider the two descriptions in the boxes and discuss the questions as a group.

Expected outcomes The zinc strip becomes coated with copper. If left for longer, the copper may start to form clumps and sink to the bottom of the tube. Over time, the colour of the solution may fade.

Safety notes Wear eye protection and wash any splashes off skin immediately.

Answers 1 Zinc cannot be plated onto iron by displacement. Zinc is more reactive than iron. 2 Silver can be plated onto iron by displacement. Silver is less reactive than iron.


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Differentiation

Practical

Pupils look at zinc displacing copper and consider other applications of displacement.

Core


UG LP

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TN


boiling tube and rack 0.4 mol/dm3 copper sulphate solution zinc strip approx same length as boiling tube and narrow enough to fit in boiling tube

Zinc strip should be cleaned shortly before use by dipping into dilute hydrochloric acid, then dilute sodium hydroxide and then rinsing. Strips can be reused by washing and treating with dilute acid as above.

For your information Running the activity Pupils set up the experiment as shown on Activity sheet F3b. Pupils work in groups to explain their ideas about what is happening. They need to link their observations of copper plating the zinc strip to the idea that zinc is more reactive than copper. More able pupils may be encouraged to think about what would happen to the colour of the copper sulphate solution over time. Pupils should then consider the two descriptions in the boxes and discuss the questions as a group.

Expected outcomes The zinc strip becomes coated with copper. If left for longer, the copper may start to form clumps and sink to the bottom of the tube. Over time, the colour of the solution may fade. Safety notes Wear eye protection and wash any splashes off skin immediately.


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Displacement reactions can be used to put a thin coating of one metal on another. You are going to see how this works. 1

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Fill a boiling tube about half full with copper sulphate solution. Stand a zinc strip in the tube. Look at the strip after a few minutes. Work as a group to think about what you see. Make a large coloured diagram of your observations. Write explanations in bubbles around your diagram to explain the changes. Your explanation should include: 





5

a word equation ideas about reactivity of metals ideas about displacement.

Wear eye protection. Wash any splashes of copper sulphate solution off your skin immediately.

strip of zinc

copper sulphate

Look at the boxes below. Work as a group to answer the questions. Galvanised iron is used to make barriers and fences. It is made by putting a thin coating of zinc on iron. Putting a thin layer of one metal on another metal is called plating. 1

Can iron be plated with zinc by dipping iron into zinc sulphate solution?

Explain your reasoning.

Silver plated jewellery is made by putting a thin plating of silver on another metal, such as iron. 2

Can iron be plated with silver by dipping iron into a solution of a silver salt?

Explain your reasoning.


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Atoms and ions

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Type

Purpose

Differentiation

Paper

To give the most able of able pupils extension work which will help satisfy their curiosity about what is happening during reactions, using the example of a displacement reaction

Extension


It is assumed that these rare pupils will be working alone. However, the activity UG LP may generate more questions than it answers!

Expected outcomes The pupil understands the sheet and can manage the questions without further help. If they need more help, they are probably not working at the necessary level.

Answers 1 a A positive ion is an atom that has lost electrons. b Na+ is an atom of sodium that has lost one electron and is now a positive ion. c Al3+ is an atom of aluminium that has lost three electrons and is now a positive ion. 2 Lithium +beryllium ions → lithium ions +beryllium 2Li +Be2+ → 2Li + +Be

+3

+3

2 electrons from lithium

+4

beryllium ion


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Atoms and ions

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Activity Extension

You are going to learn about atoms losing or gaining electrons during reactions. Read the following information carefully, then answer the questions.

Atoms and ions


In sodium metal, each atom of sodium has 11 electrons.

If you put a sodium compound with aluminium metal, nothing happens. Aluminium is less reactive than sodium, so aluminium cannot displace sodium from its compound.

+11

An atom of sodium in a compound like sodium chloride or sodium oxide has lost an electron. It still has 11 protons in its nucleus, but it now has only 10 electrons.

If you put an aluminium compound with sodium, a reaction occurs. Energy is given out, a sodium compound is made and the aluminium ends up as the metal.

Each proton has a charge of +1, so the nucleus has a charge of +11. Each electron has a charge of –1, so the electrons have a charge of –10. Overall the atom has a charge of +1. We call a charged atom an ion. Sodium atoms in compounds are +1 ions. These are written as Na+.

sodium +aluminium ions → sodium +aluminium + 3Na + Al3+ → 3Na + Al

+11

1 electron 'lost'

Reactive metals, like sodium, are not found in nature. All the sodium atoms are found as sodium ions in compounds. Sodium atoms always react to lose their outer electrons and form sodium ions.

3 electrons from sodium → aluminium

In aluminium metal, the atoms +13 have 13 electrons each. In aluminium compounds, all 3 outer 3 electrons 'lost' electrons have been lost. This means the aluminium compound contains +3 ions. 1

In the example above, sodium is more reactive than aluminium, so aluminium ends up with the ‘unwanted’ electrons.

Explain, in your own words, what these scientific terms mean: a

2

You can think of displacement reactions as a competition between metals to become ions, by getting rid of ‘unwanted’ outer electrons. The more reactive a metal, the more effective it is at getting rid of these outer electrons.

positive ion

b

Na+

c

Al3+

Lithium (Li) has atomic number 3, so it has one electron in its outer shell. Lithium loses its one outer electron when it becomes a compound. Beryllium (Be) has atomic number 4, so it has two electrons in its outer shell. It loses its two outer electrons when it becomes a compound. Lithium is more reactive than beryllium. What will happen when lithium metal is mixed with a beryllium compound? Represent this reaction using a word equation, a balanced symbol equation and a diagram.


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UG LP

Using reactivity data


Type

Purpose

Differentiation

Paper

Pupils use data from two experiments, one involving temperature change, to rank metals in order of reactivity.

Core (Extension)

Running the activity Pupils need experience of the types of data handling question they may encounter in the SAT for KS3 Science. This question leads pupils through an analysis of two sets of data. Pupils use data from two experiments to work out a reactivity series.

Core: The Activity sheet leads pupils through the argument. Extension: This extends the task to include asking pupils to think about ideas of energy changes in the reaction.


Expected outcomes Pupils realise that Justin’s data cannot give a full reactivity series, but that Vishal’s can. They deduce a reactivity series based on Vishal’s data.

Pitfalls There is a problem in that the larger the temperature rise, the less reactive the metal (as compared to magnesium). This will confuse many pupils, and the teacher should be able to give guidance.

ICT opportunities It would be possible to set up a spreadsheet for the results and ask pupils to produce bar charts to display them.

Answers Core: 1 B (with zinc) and C (with magnesium). There is a new substance being made because bubbles are observed. 2 a More bubbles/faster bubbles (of hydrogen). b Zinc is less reactive than magnesium. The other three are less reactive than zinc. 3 A temperature change happens when a chemical reaction occurs (due to energy being given out). 4 a Magnesium produces the largest temperature change. b Magnesium, zinc, iron, lead, copper. Extension: 5 magnesium +hydrochloric acid → magnesium chloride +hydrogen zinc +hydrochloric acid → zinc chloride +hydrogen 6 magnesium +zinc nitrate → zinc +magnesium nitrate Mg +Zn(NO3)2 → Zn +Mg(NO3)2 7 More reactive metals give out more energy when they react, leading to bigger temperature changes. Very able pupils may appreciate that it is the difference in reactivity between the two metals that determines the amount of energy given out. ©Harcourt Education Ltd 2004 Catalyst 3 This worksheet may have been altered from the original on the CD-ROM.

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Using reactivity data

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Activity Core

You are going to use secondary data from two experiments to work out a reactivity series.

Considering the evidence Experiment 1 Justin added a spatula of metal filings to 2 cm3 of dilute hydrochloric acid. He observed that bubbles were produced immediately. The diagram shows what Justin observed. Experiment 2 Vishal added a spatula of magnesium powder to five different salt solutions and measured the temperature rise. 1

2

Study Justin’s results. Explain how you know that there is a chemical reaction occurring in some of the test tubes but not others. a

b

iron

zinc

magnesium

lead

copper

Test tube Type of salt

Temperature (°C)

A

iron nitrate

36

B

zinc nitrate

15

C

magnesium nitrate

D

lead nitrate

0 41

How do Justin’s results E copper nitrate 46 show that magnesium is the most reactive metal? What can you conclude about the reactivity of the other metals from Justin’s results?

3

Study Vishal’s results. Explain how you know that there is a chemical reaction occurring in some of the test tubes but not others.

4

a b

How do Vishal’s results show that magnesium is the most reactive metal? Use Vishal’s results to put the five metals in order ‘most reactive’ to ‘least reactive’.

Extension 5 6

7

Write a word equation for one of the reactions in Justin’s experiment. Mg(NO3)2 Write a word and symbol equation for the reaction between magnesium and zinc nitrate in Vishal’s experiment. Use the Zn(NO3)2 symbols in the box to help you. Explain, using ideas about chemical change and metal reactivity, why different metals gave different temperature changes in Vishal’s experiment.


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Uses of metals


Type

Purpose

Differentiation

Discussion

Pupils carry out research about a metal. They present their findings to the whole class as part of a presentation activity.

Core Resource (C, H, E)


Finding relevant information is very time consuming. Give pupils the briefing cards at the end of lesson F4 and ask them to carry our web searches for homework. Alternatively, provide UG LP packs for each group containing relevant printouts of suitable websites. Properties and processes can be found in standard textbooks. See below for suggested websites. Tell pupils that more than one group is carrying out research into the same metal so it is important that they stick to the questions they are asked to look at. Pupils can present their information in a number of ways. They can be given OH Ts to use as visual aids to a short talk, or they can make posters, leaflets or magazines. If time allows they can produce their presentation electronicall y. Ask each group to make a short, timed presentation to the rest of the class. If pupils are confident, you can formalise this by having an orange and red card system, as is used in formal public speaking contests. When the speaker strays from the point, other pupils hold up an orange card and a red card means ‘out of time.’

Other relevant material Skill sheet 4: Web searches F5a Resource

Pitfalls Warn pupils not to copy out large amounts of information they do not understand. They do not need, for example to understand the processes in the Blast furnace or electrolysis of aluminium. They need to know in outline how the metals are extracted.

ICT opportunities It would be possible to set up a database to present properties of metals. Pupils may also like to present the properties in electronically produced tables. Useful websites… Gold:

Nine carat gold website Cambrian GoldFields Ltd: gold authentication (this site includes information about hallmarking)

Iron:

Steel Recycling Institute

Copper: Schoolscience Element properties: WebElements Periodic Table


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Uses of metals

Activity Core

You are going to work in a group to research and present information about a metal. 1

Look at the briefing card your teacher gives you. It will guide your research on a particular metal.

Think about ...

UG LP 

TN







How will you divide up the tasks in your group? How will you research your metal? You can use books or carry out web searches. You need to make sure not to copy out information you do not understand– some of the information you will find will be too technical. Use only the interesting aspects that will appeal to other people in your class. You might be able to find out some ‘Fun facts’ about your metal that you can use. How will you present the information to make it as interesting as possible for the rest of the class? You might decide to use charts, graphs, tables, posters, OHTs or write your presentation using a computer. You might consider putting your research together to make a booklet.


F5a

Uses of metals

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Activity Core

You are going to work in a group to research and present information about a metal. 1

Look at the briefing card your teacher gives you. It will guide your research on a particular metal.

Think about ... 







How will you divide up the tasks in your group? How will you research your metal? You can use books or carry out web searches. You need to make sure not to copy out information you do not understand– some of the information you will find will be too technical. Use only the interesting aspects that will appeal to other people in your class. You might be able to find out some ‘Fun facts’ about your metal that you can use. How will you present the information to make it as interesting as possible for the rest of the class? You might decide to use charts, graphs, tables, posters, OHTs or write your presentation using a computer. You might consider putting your research together to make a booklet.


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Patterns of Reactivity SOW.pdf

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