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Pupil's Book C

Chapter 2 Reactions of metals and the reactivity series

Rationale

Pupil's Book C Chapter 2 covers two units of the QCA Scheme of work, Unit 9E Reactions of metals and metal compounds, and Unit 9F Patterns of reactivity. This has been done deliberately to make the timings of the units in Year 9 more manageable. Units 9E and 9F have a lot of concepts in common, so it makes sense to treat the two as a continuum and not to break in between them. The lesson plans included here cover 12 hours of lessons, instead of the QCA recommended 15 hours. Part of this reduction is because there is now only one introduction and one revision/test session for the two QCA units. Other reductions have come by not covering in such depth concepts such as acids that are generally well learnt in Year 7. Further reduction of the time is possible. There is a lot of practical work in the unit that can be left until the post test period. Additionally the symbols and equations work may be omitted for pupils who progress less quickly. The chapter traces the content of the metals topic from properties of metals and non-metals to reactions with acids, neutralisation reactions, reactions that make salts, metal and non-metal oxides; then to occurrence of metals and their extraction; and finally to the reactivity series. Many of the reactions demonstrated to and carried out by pupils in this section will require safety screens, eye protection and risk assessments. module of several GCSE courses including the popular AQA modular course. The use of symbol equations as well as word equations is needed for a Higher level approach to GCSE.

Common misconceptions

Pupils need to be reminded that metals are a class of materials. Mixtures of metals are called alloys. These include brass, bronze, solder and the lightweight `alloy' as used in car wheels and aeroplanes. Pupils will need to be reminded about steel. Steel is a curious alloy as it contains mainly iron atoms. Steel reacts chemically in the same way as pure iron, but it is stronger and has different magnetic properties. Pupils will also need reminding about the nature of atoms and molecules. They may need a recap of the patterns in the Periodic Table. The concept of the ion is introduced in this chapter. It may be best to describe this particle as `like an atom or molecule but carrying an electric charge'. Beware of the following misconceptions: All metals rust. All metals are magnetic. Pupils don't consider different metals to be different substances, just `a different colour of metal'. All metals have similar properties to steel. There is confusion between many elements and their compounds, for example calcium in bones and milk. Pupils think that there is only one type of salt. All acids are dangerous corrosive substances. Pupils are very confused by the chemical use of the word `base'. Pupils do not associate sulphate with sulphuric acid and so on for other acids. Gases are not matter because most are invisible. Gases do not have mass. Mass and volume, which both describe an `amount of matter', are the same property. Particles of solids have no motion. Relative particle spacing among solids, liquids and gases (1:1:10) is incorrectly perceived and not generally related to the density of the states. Materials can only exhibit properties of one state of matter. Particles possess the same properties as the materials they compose. For example, atoms of copper are `orange and shiny', gas molecules are transparent, and solid molecules are hard. Melting, freezing and boiling, and condensation are often only understood in terms of water. Particles are viewed as mini-versions of the substances they comprise.

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Conceptual development

Pupils will need to build on their kinetic theory of matter and concept of conservation of matter. All of the chemical changes in this chapter are described using word equations, and symbol equations are introduced for most of these reactions. Pupils will need to be familiar with atomic symbols. It is particularly important to teach Na, K, Cu, Fe, Ag, Hg and Pb. Pupils will need to know the conventions about formulae in equations. They will need to be able to state the number of atoms represented by formulae such as Ca(OH)2 or K2SO4.

Building on previous learning

Properties of metals were covered in Pupil's Book B, Chapter 2 (QCA Unit 8E). Reactions of metals with the air and corrosion of metals have been covered significantly in Pupil's Book A, Chapters 8 and 11 (QCA Unit 7E and Unit 7F).

Future learning

A great deal of this material is revisited in the `Metals'

Pupil's Book C Chapter 2

Particles are often misrepresented in sketches. No differentiation is made between atoms and molecules. Particles misrepresented and undifferentiated in concepts involving elements, compounds, mixtures, solutions and substances. Frequent disregard for particle conservation and orderliness when describing changes. Absence of conservation of particles during a chemical change. Chemical changes perceived as additive, rather than interactive. After chemical change the original substances are perceived as remaining, even though they are altered. Failure to perceive that individual substances and properties correspond to certain types of particles (i.e. formation of a new substance with new properties is seen as simply happening rather than as the result of particle rearrangement).

Recognise that chemical reactions can be modelled by assuming that atoms can rearrange themselves, and that this can happen in only a limited number of ways, e.g. A B AB, AB CD AD CB. Use the particle rearrangement model to: ­ predict the names and formulae for products that might be formed from given reactants; ­ write word and symbol equations for some simple reactions; ­ explain why mass is conserved in chemical reactions. Describe how metals react with: ­ oxygen, water, acids and oxides; ­ solutions of salts of other metals. Identify differences in reactivity of metals to construct a reactivity series; use this to explain uses of metals and make predictions about the reactions of metals.

Match to

National Curriculum references

3.1 Classifying materials a) how materials can be characterised by melting point, boiling point and density c) that the elements are shown in the periodic table and consist of atoms, which can be represented by symbols d) how elements vary widely in their physical properties, including appearance, state at room temperature, magnetic properties and thermal and electrical conductivity, and how these properties can be used to classify elements as metals or non-metals f ) to represent compounds by formulae and to summarise reactions by word equations. 3.3 Patterns of behaviour a) how metals react with oxygen, water, acids and oxides of other metals, and what the products of these reactions are b) about the displacement reactions that take place between metals and solutions of salts of other metals c) how a reactivity series of metals can be determined by considering these reactions, and used to make predictions about other reactions d) to use indicators to classify solutions as acidic, neutral or alkaline, and to use the pH scale as a measure of the acidity of a solution e) how metals and bases, including carbonates, react with acids, and what the products of these reactions are f ) about some everyday applications of neutralisation h) to identify patterns in chemical reactions.

Suggestions

Thinking skills opportunities

The reactivity series experiments are useful activities for recognising patterns in data. The reactions of metals generally obey the same principles, but there seem to be large differences e.g. between heating magnesium and copper in air. Reconciling these differences is a `thinking challenge'.

Key vocabulary

airframes; argon; barbecue; base (chemical); carbon monoxide; chromium; coinage; conduction; corrosion; displacement reaction; ductile; electrolysis; graphite; hydrogen peroxide; hydroxide; ion; limescale; lithium; malleable; manganese; metallic; non-metallic; potassium; phosphoric acid; phosphorus; reactivity; silicon; sodium; spectator; stainless steel; tarnish; tartaric acid; thermit; titanium; tough; wooden splint

Answers

Answers to questions in Starter Activity and Finishing Off

Starter Activity

Scheme of work section

This chapter matches all the content of both Unit 9E (Reactions of metals and metal compounds) and Unit 9F (Patterns of reactivity). This is a deliberate attempt to group similar concepts together for greater teaching effectiveness.

Yearly teaching objectives

Identify evidence which indicates that a chemical reaction has taken place, such as the association of energy transfer with chemical change.

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1 Air is a mixture of gases, mainly nitrogen with onefifth oxygen. 2 A pure substance formed from two or more elements. 3 By distillation 4 It is (mainly) sodium chloride. 5 A substance made from only one type of atom. 6 The smallest particle of matter that can exist on its own. 7 They are the basic building blocks for all materials. 8 Iron, lead, copper, silver, gold ­ look at the Periodic Table, Pupil's Book B, page 151. All the `pink' elements are metals. 9 Brass is a mixture of copper and zinc. Bronze is a mixture of copper and tin. They are not pure substances. Mixtures of metals are called alloys. 10 Chlorine, sulphur, carbon, nitrogen ­ and all the `yellow' elements in the Periodic Table, Pupil's Book B, page 151. 11 One hundred million atoms, but the line is very narrow. 12 A list of all the elements in order of atomic number.

Pupil's Book C Chapter 2

13 On the left-hand side (see Pupil's Book B, page 151). 14 H Hydrogen O Oxygen N Nitrogen Mg Magnesium S Sulphur Al Aluminium C Carbon Ca Calcium 15 Na Sodium K Potassium Fe Iron Cu Copper Ag Silver Pb Lead 16 Oxides 17 Oxygen atoms join with the metal atoms to make heavier materials. 18 Molecules 19 Water H2O; carbon dioxide CO2 20 Nitrogen N2, Chlorine Cl2, Fluorine F2, Bromine Br2

Finishing Off!

1 a) b) c) 2 a) b) c) 3 a) b) c) 4 a) b) c)

Crystals of lead solid on magnesium Heat, flame and vapours Fizz, gas given off, copper carbonate disappears lead nitrate magnesium magnesium nitrate lead ethanol oxygen carbon dioxide water copper carbonate sulphuric acid copper sulphate carbon dioxide water Pb(NO3)2 Mg Mg(NO3)2 Pb C2H5OH 2O2 2CO2 3H2O CuCO3 H2SO4 CuSO4 CO2 H2O Displacement Combustion/oxidation Neutralisation/gives off gas

2 Any others of the properties above 3 Graphite/carbon 4 Any three of hydrogen, oxygen, nitrogen, chlorine, helium, argon, neon, xenon, krypton, radon. 5 Hydrogen 6 Put a lighted splint into a test tube full of the gas and it burns with a squeaky pop. 7 A ­ Add the calcium carbonate to the acid. B ­ Filter the mixture. C ­ Leave the remaining solution to evaporate and crystallise. 8 A substance that neutralises an acid to produce new water molecules. 9 The copper oxide would dissolve; the solution would turn blue. 10 Calcium chloride 11 a) Magnesium carbonate hydrochloric acid magnesium chloride water carbon dioxide b) Copper carbonate hydrochloric acid copper chloride water carbon dioxide c) Sodium carbonate sulphuric acid sodium sulphate water carbon dioxide 12 Zinc oxide sulphuric acid zinc sulphate hydrogen 13 They have reacted with other elements to form compounds. 14 Most reactive: Satisium Digitium Webium Least reactive: Earthium 15 a) A reaction b) No reaction c) A reaction 16 Sodium melts and rushes around the surface; a gas is given off. 17 Lithium water lithium hydroxide hydrogen

Answers to End-of-unit test

1 Any three of: shiny, ring like a bell, ductile, malleable, conduct electricity, conduct heat well

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Chapter 2

Target sheet

Tick off the list as you work through Chapter 2 when you are happy that you understand the following:

YTOs

Target I know what a metal looks like. I can write a list of the properties of metals. I can describe how air reacts with metals. I can describe how water reacts with metals. I can describe how acids react with metals. I can describe how acids react with metal carbonates. I can describe how acids react with metal oxides. I know what a (chemical) base is. I can carry out experiments on metals and metal compounds. I can write word equations for reactions. I can write symbol equations. I can write and use chemical formulae. I can name a salt if I know which chemicals it was made from. I can test a gas to see if it is hydrogen. I can test a gas to see if it is carbon dioxide.

Tick

I know about the reactivity series for metals. I can place metals in the reactivity series by observing them reacting. I can make predictions by using the reactivity series.

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Hodder Science Teacher's Resource C © 2003 Hodder & Stoughton Educational

Chapter 2

1 2 3 4 5 6 7

End-of-unit test

Name three properties of metals. (level 3, 1 mark) Name three more properties of metals. (level 3, 1 mark) Which non-metal element conducts electricity in one particular form? (level 3, 1 mark) Name three elements that are gases. (level 3, 1 mark) What element is given off when metals react with acids? (level 4, 1 mark) How do you test for the element that is the answer to Question 5? (level 4, 1 mark) Fill in the missing stages in these instructions for making a salt.

Keep adding the carbonate until no more fizzing occurs and some solid is left in the mixture Reduce the volume of the solution by boiling

Measure out the correct amounts of calcium carbonate and hydrochloric acid

A (level 3, 1 mark)

B (level 4, 1 mark)

C (level 3, 1 mark)

8 What is a chemical base? (level 5, 1 mark) 9 If copper oxide (black powder) was mixed with warm sulphuric acid (colourless solution) and stirred, what two things could you expect to see happen? (level 5, 2 marks) 10 What salt is made when calcium reacts with hydrochloric acid? (level 3, 1 mark) 11 Copy and complete: a) Magnesium carbonate hydrochloric acid _____________ water carbon dioxide (level 4, 1 mark) b) Copper carbonate hydrochloric acid copper chloride _______ ______ (level 5, 2 marks) c) _____________ _____________ sodium sulphate water carbon dioxide (level 5, 2 marks) 12 Put this symbol equation into words: H2 (level 5, 2 marks) ZnO H2SO4 ZnSO4 13 Explain why very few metal elements are found as unreacted metal in the Earth's crust. (level 6, 1 mark) 14 Here are the results of some displacement reactions. List the metals in order of reactivity with the most reactive first. no reaction a reaction is seen

Satisium nitrate solution Satisium Earthium Webium Digitium ­ Earthium nitrate solution ­ Webium nitrate solution ­ Digitium nitrate solution ­

(level 6, 1 mark) 15 If these mixtures were heated, would there be a reaction between the two substances? (Reactivity series: Magnesium > Aluminium > Zinc > Iron > Copper) a) Copper oxide magnesium powder b) Aluminium oxide zinc powder c) Iron oxide aluminium powder (level 6, 3 marks) 16 What two things do you see happen when sodium is put into cold water? (level 7, 2 marks) 17 Write a word equation for the reaction between lithium and water. (level 7, 1 mark)

Hodder Science Teacher's Resource C © 2003 Hodder & Stoughton Educational 27

Pupil's Book C Chapter 2

2.1 We need metals

Rationale

Pupils will know a great deal about metals from Year 7 (reactions of acids and metals) and Year 8 (metal atoms as building blocks for compounds). This spread could be shortened or omitted to make room in the crowded Year 9 programme if pupils fully understand about the properties of metals. used and link it to a possible name for the metal. There are cards to print out with the properties and names of the metals.

Homework

Homework 2.1 Which metal for the job?: Pupils have to match up metals to one of their common uses.

Suggested starter

Learning outcomes

Most pupils will learn: the properties of metals and how they relate to the uses of metals what alloys are and how they improve the properties of metals the difference between metals and non-metals the names of non-metallic elements. The faster pupils will: learn about the different levels of metal production and relate it to uses understand the physical differences and chemical similarities between iron and steel. Those who learn less quickly will learn that: there are two distinct groups of elements metals have a unique set of useful properties.

Starter A Useful or not ­ non-metals?: This activity allows pupils to find out some of the uses of nonmetals that they might not know. They may need some prompts to complete the activity.

Main activity

Lesson plan

2 hours/lessons

Suggested starters

Activity 2.1 Investigating metal fatigue: This is a good Sc1 activity on the flexibility of metals, providing pupils with practice in planning experiments and recording evidence. The activity sheet gives only a draft idea for the pupils to investigate. The pupils themselves will need to flesh out the ideas when they write up their account of the work. This makes a good activity to present as a poster. Liaison with the technology department may produce further work. (Note: Look at Finisher B Titanic: This would make an extension or alternative to the experiment).

Suggested finisher

Use the Starter Activity on page 15 of Pupil's Book C. This Periodic Table quiz will help revise knowledge of metals, non-metals and their properties from Book B of the Hodder Science course. Show pupils as many samples of metal objects as you can find, including alloys. Get pupils to name all the metal materials. List all the metal objects and compile a quiz so pupils can guess what materials they are made from. (D&T departments can contribute samples of many metals that will not be found in the science department.)

Main activities

Finisher B Titanic: This is an interesting extension to Activity 2.1. It uses the context that the steel of the Titanic had a high ductile-brittle transition temperature (but was as good as it got in that era). The seawater round the Titanic and iceberg was at 2 oC, because of the saltiness of the North Atlantic.

Homework

For homework get the pupils to draw a mind map or concept map to sum up their previous knowledge about the particle model. Give them this list of 20 words to incorporate and link in their `mind map'. particle liquid atom element reaction density air nitrogen water vapour metal solid gas molecule compound chemical change Brownian motion oxygen argon and rare gases carbon dioxide non-metal

Work through Spread 2.1 of Pupil's Book C, read the text as a class and answer the questions. Use practical activities to investigate the properties of metals: A Do heat and electrical conductivity tests on a variety of materials, some metallic and some nonmetallic elements, for example roll sulphur and carbon rods. B Compare the brittleness of materials. Demonstrate the brittleness of roll sulphur and carbon rod. Teach pupils that they are strong, but break when even slightly bent. (Note: see also alternative activities in QCA SoW 9E Section 1.)

Suggested finisher

Suggestions

Literacy

There are many works of fiction that describe uses of the properties of metals. Often science fiction has accounts of exciting `new' metals (e.g. War of the Worlds by H.G. Wells) that are so tough they cannot be drilled, cut or welded. Make up a page of some excerpts and get pupils to write about them as a homework activity. Make sure that all the words relating to properties of metals are understood e.g. sonorous, malleable, ductile.

Finisher A Metal pictures: This is an ICT/photo based activity. Print out the ten photos of metals in use. Pupils need to identify the property of the metal being

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Pupil's Book C Chapter 2

Work on the difference in concept between strong, hard and tough. For example brick is strong and hard but shatters easily, so it is not tough. Leather is strong and tough, but as it is flexible it is not hard. Steel girders are strong: they will withstand a lot of force. They are hard: they will scratch many other surfaces. And they are tough: they flex a little under load but they do not break.

ELECTRICITY Batteries (1.5V) Battery holder Bulb holder and bulb (either 1.5V or 1.25V) Crocodile clips/4 mm plug leads (depending on type of battery holders available) Materials from (1) sulphur roll (flammable) and carbon rods Experimental notes 1 1 1

Numeracy

Possible activities: Work out a table of densities for different metals, given the mass and volume data (re-cap of Year 7 work). Draw a bar chart of the world production of different metals (see Pupil's Book C page 17).

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1 set

ICT

Use CD-ROMs such as The Chemistry Set from New Media and CD-ROM encyclopaedias like Encarta 2000 from Microsoft and Hutchinson's to find images and information about uses of metals. Use web searches to find more information about metals.

Sc1 Ideas and evidence

There are only limited opportunities for whole investigations, as pupils have a limited understanding of why certain metals are used for certain applications. Data analysis activities are a good method for practising pattern finding in data.

Cover friendly rating

3 star (activity); 4 star (textbook); 4 star (Homework)

Cross curricular links

D&T (uses of metals and their properties), Geography (sources and world production of metals)

* Suggestions for metal objects: nails, brass screws, gold ring, aluminium foil, teaspoon, tin can, drinks can, solder, magnesium ribbon (see appropriate CLEAPSS Hazcard), metal pencil sharpener, paper clip, key, nichrome wire, ball bearing, spanner, copper wire (swg 18). Provide, if applicable, in a resealable clear plastic bag. Before using sulphur roll, consult the appropriate CLEAPSS Hazcard. When heating sulphur, use no more than 2 g in a test tube. Plug the tube with mineral wool to minimise sulphur vapour escaping and catching fire. Heat slowly with a small Bunsen flame with the collar half open. If molten sulphur is to be poured onto cold water, this must be done in a fume cupboard. If sulphur is to be burnt, use no more than 0.05 g per group in the open lab since sulphur dioxide is formed. For larger amounts, use a fume cupboard. Provide small pieces of wax, from a candle, the piece should be small enough so that the Vaseline will hold it on to the surface of the item being heated.

Technician's notes

Possible teaching strategies

Equipment

1 Names of metals Metal objects* 2 Properties of metals HEAT Bunsen burner, bench mat Matches Materials from (1) + sulphur roll and carbon rods Retort stand, boss head and clamp Sellotape Test tubes Tongs Vaseline Wax Eye protection 1 1 1 1/student 1 1 1 set 1 1 1­2 sets /class

Activity 2.1

Equipment Quantity/group

Paper clips small, medium, large Paper clips Microscope (any microscope or hand lens, which has a magnification of 10 or above, would be suitable)* Microscope slide and sellotape (have available) Copper wire

Quantity/group

3 of each/group 15 of each size

1 4­5 3­4 pieces 3­4 pieces 3­4 pieces 3­4 pieces 3­4 pieces 3­4 pieces 1

Magnesium ribbon¶ (Highly flammable) Steel strip¶*

Brass strip¶* Aluminium strip¶* Copper strip¶* Protractors Experimental notes

* Set up the microscopes so that the iris (if fitted) is closed (to the left) and the mirror is set to give the best light and the 10 (or 8) objective lens is in the viewing

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Pupil's Book C Chapter 2

position. If a standard light microscope is used, provide microscope slides and sellotape so that the students can stick the paperclip to the slide for ease of viewing. Put the microscope slides into a covered shallow plastic pot or used Petri dish with a piece of paper towel. Provide the wire cut to the approximate length of a large paper clip. ¶ See appropriate CLEAPSS Hazcard. Provide the ribbon cut to the approximate length of a large opened-out paper clip with the required hazard label. ¶ * These should be obtainable from the CDT department and should, if possible, be of the same size and thickness.

6 Iron is 100% iron Steel is 99.6% iron; the rest is carbon 7 579,812 tonnes 8 Iron, aluminium, manganese, copper 9 Iron for the construction industry, manganese for stainless steel, aluminium for manufacturing, copper for electrical cables 10 86% of the world's production is iron 11 Steel is made from pure iron 12 a) Gold and silver b) Their rarity makes them valuable

Answers to Starter A

1 sulphur, 2 phosphorus, 3 chlorine, 4 iodine, 5 helium, 6 nitrogen, 7 fluorine, 8 argon, 9 carbon, 10 neon, 11 silicon, 12 iodine, 13 arsenic, 14 hydrogen, 15 oxygen, 16 nitrogen, 17 silicon, 18 carbon, 19 chlorine, 20 carbon.

Answers

1 strong, hard, tough, drawn out into wires, shiny, able to be bent, make a nice noise when hit, conduct heat and electricity, some are magnetic 2 Alloys are mixtures of metals 3 By mixing molten metals 4 carbon, oxygen, hydrogen, nitrogen, chlorine, sulphur, phosphorus, silicon 5 Non-metal element

carbon oxygen hydrogen nitrogen chlorine sulphur phosphorus silicon

Answers to Finisher A

Property

hard heavy shiny high melting point flexible strong valuable conducts heat conducts electricity magnetic

Picture

saw teeth fishing weights silver jewellery filament in bulb kitchen foil scaffolding coins copper pan pins on plug fridge door

Metal

steel aluminium silver tungsten aluminium steel gold copper brass steel

What state of matter is it?

solid gas gas gas gas solid solid solid

Description of what it looks like

dull grey colourless colourless colourless yellow green yellow powder waxy white shiny grey

Match to

National Curriculum references

3.1 d, g, h

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Chapter 2

Activity sheet

2.1 Investigating metal fatigue

Metals are flexible materials and that is one of their most useful properties but a piece of metal will not go on flexing forever. Eventually the metal breaks. Can you answer this question? Try brainstorming the idea in a small group. What factors could affect how much flexing it takes to cause a piece of metal to snap? A good method is to try a few trial runs. For this, a paper clip is a good item to investigate. Unbend the paper clip to the shape shown in the diagram. Flex it back and forth until it snaps in two. Count the number of times you have to flex it before it snaps. Look at the broken ends through a microscope.

Try changing the angle of the bend ­ how does this affect the time until the clip snaps. Try out different thicknesses of paper clip. Try twisting it and bending it. Try out other materials, such as copper wire or magnesium ribbon of similar thickness.

Make a record

Write a series of ideas and predictions about the way fatigue works. Choose one factor to investigate ­ you can do more than one, but do them one at a time. Decide on a range of results that you can take. This may depend on what thickness or type of material you can find. Collect data about how much bending it takes to break the object. Here are some suggestions of tables you could fill in:

Size of paper clip Small Angle of bend 10 Type of material Copper Number of 90 bends until it breaks Repeat 2 Repeat 3 Average Number of bends till clip breaks Repeat 2 Repeat 3 Repeat 1 Number of 90° bends till it breaks Repeat 2 Repeat 3 Average

Repeat 1

Average

Repeat 1

To evaluate

"Usually it's not just one bend that causes metal fatigue. Normally it's the cycle of lots and lots of little bends backward and forward that eventually causes the damage." Evaluate whether this idea is correct in the write up of your investigation.

Hodder Science Teacher's Resource C © 2003 Hodder & Stoughton Educational 31

Chapter 2

Homework sheet

2.1 Which metal for the job?

All the metals have applied for the job of being the wire in a new sound system. They have each written a short `CV' to describe the job they do, but the names have been left off them.

So try this

Copy out the list of metals and write the correct `CV' sentence next to each metal on the list. Decide which metal gets the wiring up job.

List of metals

Sodium, iron, uranium, tin, calcium, mercury, copper, aluminium, tungsten, platinum

CV extracts

I am always in light bulb filaments. I am a radioactive nuclear fuel. I am hard and I am used more than any other metal. I am a very chemically reactive metal. I am the most expensive of the precious metals. I have always had the kitchen foil jobs. I'm often the metal for water pipes, because I don't react with water. I protect the inside of metal cans. I am in limestone rock and in teeth. I am the only liquid metal.

Questions: Think about their properties

1 2 3 4 5 6

Why is uranium dangerous? Why is tin used to protect steel cans? Why is tungsten used for light bulb filaments? Why is platinum used for jewellery? Why is mercury used in thermometers? Why is sodium kept in oil?

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Pupil's Book C Chapter 2

2.2 Acid patterns

Rationale

Most pupils will have come across the reactions of acids in Year 7 (Hodder Science Pupil's Book A Chapters 8 and 11; QCA Scheme of Work Units 7E and 7F). They should be familiar with the tests for hydrogen gas and carbon dioxide gas. Remind pupils of the tests for these gases if appropriate. It is felt that the difference between molecules and ions can be addressed at this point, so extensive use of the word `ion' occurs in this spread. The approach is graphical but needs teaching input to explain the concept that `an ion is a particle that needs to carry an electric charge to remain stable. An ion can be made from a single atom or a group of atoms. If an ion loses its electric charge it reacts to become another type of particle'. This will lead to less confusion when learning about electrolysis and higher levels of chemistry. If pupils have a thorough knowledge of acid/alkali reactions then the time spent on this spread can be reduced. the passage purported to be from a Paris newspaper. They could discuss: ­ what discovery made Antoine Lavoisier famous? ­ what was the purpose of his experiment with Monsieur Sequin? ­ why was Madame Lavoisier's role important to Antoine's work? ­ were the charges against Lavoisier true? ­ would he be convicted in modern times?

Main activity

Work through Spread 2.2 of Pupil's Book C. Pay particular attention to: The role of hydroxide and hydrogen ions in acidalkali reactions (refer back to Pupil's Book A, pages 98 onwards). The idea that `spectator ions' remain unchanged in the reaction. How to decide the name of the salt that gets formed in the reaction. Make sure as you work through the chapter that all pupils understand the rules for naming salts. Compounds with names ending in `-ate' can be described as containing a lot of oxygen. Compounds ending in `-ite' contain a smaller amount of oxygen than those ending in `-ate'. The only `-ite' compounds the pupils may come across are sulphites and hypochlorites.

Suggested finisher

Learning outcomes

Most pupils will: learn how acids react with alkalis know how to test for hydrogen and carbon dioxide know that neutralisation reactions produce salts and new water molecules know that acids and alkalis react as ions and not as molecules. The faster pupils will: understand about ions and how they are formed learn about the role of spectator ions in the formation of salts. Those who learn less quickly will: be able to name simple salts from acids know about neutralisation reactions between acids and alkalis.

Finisher C Acids bingo: Play this game to finish the lesson on a focused note. Give a small prize to the winner.

Homework

Homework 2.2 Particles and reactions: This recalls the carnival model of particle theory.

Suggested starter

This is a practical lesson and the practical itself is timeconsuming. As a focused start, group the pupils round the front bench and demonstrate the correct method for performing an acid/alkali titration.

Main activity

Lesson plan

2 hours/lessons

Suggested starter

Start the lesson with a quick quiz that provides a recap of the nature of acids, including fruit acids. Possible questions could include: ­ what sort of materials are acidic? ­ what do weak acids taste like? ­ what are the effect of strong acids on flesh? ­ what safety precautions are necessary when working with acids? Extend the quiz to include the same sorts of questions about alkalis. Starter B Lavoisier: This is an Ideas and Evidence starter activity intended to give pupils some insight into how `famous scientists' are still susceptible to political and social changes that affect their work. The activity tells how Lavoisier was accused and executed for treasonable crimes. But alternative explanations showed his work to be populist and altruistic, as well as scientific. Pupils should read

Activity 2.2 Spot-on accurate: titration: Use this activity to teach pupils about burettes, pipettes and the titration methods for finding an exact answer to neutralising an unknown solution. This is a good activity if set in the motivating context of `a pollution clean up after an acid/alkali spill'. There is a great deal of detail in the three sheets of this activity. The accuracy and repeatability of results achieved by spot-on, accurate titration is good preparation for Applied Science coursework at GCSE level.

Suggested finisher

Finisher D Metals quizword: This can be completed at the end of the lesson or for homework. (Note: pupils may need the whole of the session to complete and write up the practical activity. In this case the quiz word can be used as the homework.)

Homework

Pupils should either complete Finisher D or they may need homework time to write up and process the data from the practical activity.

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Pupil's Book C Chapter 2

Suggestions

Literacy

The similar names of compounds and the construction of names mentioned above can give rise to useful vocabulary and pronunciation activities. A possible creative writing activity is to get the pupils to combine an `environmental accident' story with correct scientific knowledge and understanding of how to solve the problems caused by the accident.

Hydrochloric acid 0.1M Labels/marker pens Phenolphthalein (Highly flammable) Experimental notes solution

1 1­2 1

Numeracy

Titration activities give rise to fairly challenging numeracy activities. It is advisable NOT to introduce the idea of molarity calculations for any but the fastest learners. Assume for the calculations that x cm3 of the polluted alkali river water is exactly neutralised by y cm3 of this `standard' acid solution.

ICT

Introduce pupils to the use of pH meters and the essentials of taking care of pH electrodes. Demonstrate to pupils the use of pH electrodes in a datalogging activity for neutralisation. It is the shape of the characteristic s-shaped curve when plotting pH against cm3 of solution added that is the important teaching point.

* A 100 cm3 bottle should be sufficient for each group. Make up the `river water' using 1 M sodium hydroxide (corrosive) to make a final concentration of 0.08 M sodium hydroxide (irritant). To make 100 cm3 `river water': 8 cm3 1 M sodium hydroxide, 92 cm3 water. Use appropriate CLEAPSS Recipe Card and Hazcard for procedure. See appropriate CLEAPSS Recipe Card. A 100 cm3 bottle should be sufficient for each group. See appropriate CLEAPSS Hazcard and Recipe Card. A 30 cm3 bottle, with the required hazard label, should be sufficient for each group.

Answers

1 Hydrogen ion 2 Hydroxide ion 3 An ion that takes no part in the chemical reaction and remains unchanged. 4 The picture should show only the hydrogen and hydroxide ions changing. Two nitrate ions and the calcium ion remain unchanged. 5 The picture should show only the hydrogen and hydroxide ions changing. The sulphate ion and the calcium ion remain unchanged 6 a) two, b) one 7 Name of acid

Nitric acid Sulphuric acid Sulphuric acid

Sc1 Ideas and evidence

Neutralisation is not a topic that leads to many `openended' questions at KS3 level. Use neutralisation data in analysis and graph-plotting activities.

Cover friendly rating

0 stars (activity); 2 star (textbook); 4 star (Homework sheet)

Name of alkali

Potassium hydroxide Magnesium hydroxide Potassium hydroxide Lithium hydroxide Calcium hydroxide

Name of salt

Potassium nitrate Magnesium sulphate Potassium sulphate Lithium chloride Calcium phosphate

Cross curricular links

Technology (acids and alkalis in cooking), PSHE (environmental issues)

Technician's notes

Activity 2.2

Equipment

`River water'* Beakers equivalent) (100 cm3 Pyrex or 2 1 1 1 2­3 1 1 1/student graduated) 1 1

Quantity/group

1

Hydrochloric acid Phosphoric acid

Burette (25 cm3 or 50 cm3 whichever is available) Burette clamp (retort) stand Conical flask (250 cm3 Pyrex or equivalent) Dropping pipette (plastic disposable) Filter funnel (glass or plastic) Glass rod Eye protection Pipette (25 cm3

Answers to Finisher C

1 acid solutions, 2 alkaline solutions, 3 bases, 4 a salt and water only, 5 hydrogen, 6 carbon dioxide, 7 hydrogen ion, 8 hydroxide ion, 9 ­ 5 to 6, 10 ­ 1 to 2, 11 ­ 8 to 10, 12 ­ 12 to 14, 13 red, 14 yellow/green 15 sodium sulphate, 16 magnesium chloride, 17 wash with lots of water, 18 wash with water and seek medical attention, 19 black hand and test tube, orange background, 20 caustic.

Answers to Finisher D

1 ore, 2 magnesium, 3 neutralisation, 4 conduct, 5 salts, 6 indicator, 7 hydrogen, 8 carbonates, 9 sulphur.

Match to

National Curriculum references

3.1e, f, 3.3 d, f

Pipette filler (bulb or pi-pump, whichever is available) 34

Chapter 2

Activity sheet

2.2 Spot-on, accurate: titration I

A pH measurement is not accurate enough for an environmental scientist to put right a contaminated lake or river. Often you will need to know exactly how much treatment an acid or alkali spill requires. Your task is to find exactly how much standard hydrochloric acid solution is needed to neutralise the river water. This water has accidentally had sodium hydroxide solution discharged into it from a soap factory.

burette

clamp stand acid solution

alkali river water + indicator

A burette is a long, thin measuring cylinder with a tap at the bottom. If you are careful you can use it to measure volumes of liquids to an accuracy of 1/20th of a cm3. A glass pipette is a device for measuring a set volume of liquid very accurately. (Do not confuse a real glass pipette with a plastic dropper. A plastic dropper is often called a pipette.)

Briefing notes to environmental scientist: An accurate method for measuring neutralisation

You use a burette and a pipette to measure liquids accurately. You use the change in colour of an indicator to tell whether an acid or alkali solution has been neutralised. You use a conical flask to hold the solutions while you mix them. You keep your standard acid solutions and alkali river water in separate, labelled beakers. You make observations and take readings all the way through the analysis.

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35

Chapter 2

Activity sheet

2.2 Spot-on, accurate: titration II

Pipette

Use a bulb pipette filler to fill the pipette: you may need to practise.

pipette filling up with liquid level mark at 25cm 3 pipette filler

Indicator

Use PHENOLPHTHALEIN as the indicator. Add 5­8 drops of this indicator to the alkali in the flask. This goes red in alkali and colourless in acid. The colour change is very liquid/ solution easy to see.

in beaker

Burette

Clamp the burette in a clamp stand. DON'T tighten the clamp too much ­ the burette is made of glass. Use some folded scrap paper in the jaws of the clamp. This will help hold the burette. Lift the burette onto the floor to fill it. NEVER lift solutions above eye level, EVEN IF you are wearing goggles. Fill the burette with the acid solution you are going to use. DO NOT put alkali in the burette. Alkaline solutions will attack the glass slowly. Fill the burette to ABOVE the 0 cm3 mark. Then let the acid solution run out slowly until the level of the meniscus is at the 0 cm3 mark. If you miss the 0 cm3 mark, adjust the level to the 1 cm3 mark or the 2 cm3 mark etc. You need to make a note of the exact starting point, whatever it is.

24.0

25.0 burette reading is 25.4cm 3

26.0

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Chapter 2

Activity sheet

2.2 Spot-on, accurate: titration III

Titration

The idea is to measure accurately how much acid is needed to neutralise the alkali in the flask. First do a rough estimation: add the acid in 1 cm3 portions and swirl the flask to see if the indicator changes colour. When it changes, note the result in a results table like the one below. Then re-fill the burette (lift it on to the floor!). Now do two accurate titrations. Add about 2.0 cm3 less than your rough results. Swirl this in the flask. Then add acid one drop at a time until the indicator just changes colour permanently. Record your results in a table, re-fill the burette and repeat the result to check that you were right.

Results table

Reading on burette Volume at end Starting volume Volume used Rough 1st accurate 2nd accurate

Questions

1 What was your accurate answer? 2 How close was this to the teacher's answer? 3 Describe what happens to the change in colour of indicator when you are within a few drops of the neutralisation point. 4 Is it more important that the environmental scientist gets an accurate answer or quick answer to the problem? 5 How could you improve the method you used to make it more accurate or quicker?

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37

Chapter 2

Homework sheet

2.2 Particles and reactions

This is a model for thinking about the movement of particles in different states of matter.

Questions

1 How do chemical particles move in liquids and gases? 2 Why can't two solids react easily? (Hint: movement of the particles in a solid.) 3 A piece of solid metal will react with an acid because the acid is a solution. Draw a particle picture to how and why this happens. 4 If you make the acid solution hotter, what happens to the speed of movement of the particles? 5 Draw particle pictures of 100 cm3 of very dilute acid solution and 100 cm3 of strong acid solution. Explain the difference. 6 Draw particle pictures of 100 cm3 of normal air and 100 cm3 of compressed air. Explain the difference. 7 Why do fuels burn faster in compressed air? 8 Explain two ways of making sugar dissolve faster in a beaker of water. 9 Explain why it's easier to dissolve icing sugar (powder) in water than it is to dissolve sugar lumps in the same quantity of water at the same temperature. 10 Pancakes and Yorkshire pudding are made with the same mixture. They cook at the same temperature, but pancakes take 30 seconds to cook and Yorkshire pudding takes 15 minutes. Explain why.

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Pupil's Book C Chapter 2

2.3 Acid treatment

Rationale

The series of acid neutralisation reactions need to be taken together. The concept development is that there is a clear pattern: acid acid acid base (or alkali) salt water carbonate (base CO2) salt water CO2 reactive metal salt hydrogen (base without oxygen) (water without oxygen) acids. This could usefully be a demonstration, as it requires a lot of clear observations and testing of gases. Test tubes could be clearly labelled and individual test tubes passed round the class in a test tube rack while the reaction is taking place, so that pupils can make observations. Make sure that all pupils are wearing eye protection if this demonstration is carried out. The relevant details could be highlighted by the teacher. There is a considerable amount of practical activity here. These activities in themselves could take up two hours of lesson time. Some teachers may think this is too much time to spend on making salts, but there is heavy emphasis on the different methodologies in the QCA scheme of work. The authors' suggestion would be to leave Activity 2.3b until later.

Suggested finisher

The situation with less reactive metals and acids is a difficult concept at this level.

Learning outcomes

Most pupils will learn that: alkalis are a type of base alkalis are bases that are soluble in water bases react with acids to give a neutral salt and new water molecules carbonates react like bases, except that they contain CO2 as well metals also neutralise acids to give salts only the more reactive metals react with acids. The faster pupils will learn that: the reactions of acids make them useful chemicals in several guises there is a clear pattern to the reactions of acids with other substances. Those who learn less quickly will know that: there are several materials that neutralise acids gases are often given off in acid reactions.

There is so much practical activity in this lesson that there may be no time for a focused finisher. Either work through the questions from Spread 2.3 of Pupil's Book C or use Finisher D Metals quizword if it has not been used before in the SoW .

Homework

Homework 2.3 Reactions with hydrochloric acid: Consolidates pupil's knowledge of acid and base reactions, naming salts and balanced equations.

Suggestions

Literacy

Produce a vocabulary list for this topic and test the pupils on the meanings of the words.

Lesson plan

1 hour/lesson

Suggested starter

Numeracy

All these methods require careful measurement skills.

As a starter work through Spread 2.3 in Pupil's Book C. Read the text and work through the questions orally. Emphasise that all three general types of reaction presented involve neutralising acids and making salts. Treat acid/alkali reactions as a subset of acid/metal oxide reactions. The alkali metal oxides are soluble, and become hydroxides in solution. Introduce the words `base' and `basic' to describe chemicals that neutralise acids to produce water molecules. Make clear that in chemistry `base' and `basic' have new, extra meanings.

Main activities

ICT

Activity 2.3b would be successfully aided by use of a video microscope. These are becoming very cheap and readily available. They could be used to show clearly (on a TV screen in real time) the reaction between the metal and the acid.

Sc1 Ideas and evidence

A possible investigation would be `Which substance is best at removing rust from corroded iron/steel?'. An alternative could be `What strength of solution is best to remove rust/to de-scale a boiler pipe or kettle?' Rust can be simulated by using iron oxide or iron carbonate and finding which acid dissolves it best. Calcium carbonate would be a suitable simulation of boiler scale.

This is essentially a practical-based lesson, and there are two different practical activities provided. Activity 2.3a Making salts: This is about making salts in all the different possible ways. This can be quite a lengthy activity. It would be advisable to split the salt making methods up so that not all the groups use the same method. Pupils could then deliver a presentation and swap information about the different methods. (Note: The acid/alkali method is approximately twice as long as the other methods. Some groups could just do acid/alkali, while other groups are doing two of the other three methods.) Activity 2.3b Metal plus acid: This is about comparing the reaction of metals with different

Cover friendly rating

0 stars (both activities); 2/3 star (textbook): 4 star (Homework)

Cross curricular links

D&T (rust removers)

39

Pupil's Book C Chapter 2

Technician's notes

Activity 2.3a

Equipment

Method 1 ­ Acid/alkali method: potassium chloride* Activated charcoal Beaker (250 cm3 Pyrex or equivalent) Bunsen burner, tripod, gauze, bench mat Dropping pipette (plastic disposable) Filter funnel (glass or plastic) Filter paper (student grade would be suitable) Hydrochloric acid 0.5M Matches Petri dish (a clean, used Petri dish would be suitable) Potassium hydroxide solution 0.5M¶ (Corrosive) Spatula Universal Indicator (Highly flammable) solution¶ * 1 1 1 1 1 1/student 1 3 1 3 1 1 1 1 1

Bunsen burner, tripod, gauze, bench mat

1 1 1 1 1

Quantity/group

Copper(II) oxide (Harmful)

black

Filter funnel (glass or plastic) Filter paper (student grade would be suitable) Matches Measuring cylinder or plastic) Pipette bulb) Pipette (bulb or pi-pump, whichever is available) Petri dish (a clean used Petri dish would be suitable) Sulphuric acid 0.5M (Irritant) Label or marker pen Eye protection Experimental notes 1 1 filler

3

(25 cm3

glass 1 1 1 1 1 1 1/student

(25 cm graduated or

Measuring (25 cm3 glass or plastic) Pipette or bulb)¶ (25 cm3 graduated

cylinder¶

* See the relevant CLEAPSS Hazcard for disposal of the product of the experiment. See appropriate CLEAPSS Hazcard. Supply a small amount in a labelled container with the required hazard label. Supply either measuring cylinder or pipettes and fillers, depending on availability and the abilities of the students. Equipment

Method 3 ­ Acid and carbonate: magnesium nitrate* Beaker (250 cm3 Pyrex or equivalent) Bunsen burner, tripod, gauze, bench mat Clock Filter funnel (glass or plastic) Filter paper (student grade would be suitable) Magnesium carbonate Matches Measuring cylinder (25 cm3 glass or plastic) Pipette (25 cm3 graduated or bulb) Pipette filler (bulb or pi-pump, whichever is available) Nitric acid (Irritant) 0.4M¶ 1 1 1 powder 1 1 1 1 1 1 1 1 1 1

Quantity/group

Pipette filler (Bulb or pi-pump, whichever is available)¶ Label or marker pen Eye protection Experimental notes

* See the relevant CLEAPSS Hazcard for disposal of the product of the experiment. Supply a small amount in a labelled container with the required hazard label. See appropriate CLEAPSS Recipe Card. A 100 cm3 bottle should be sufficient for each group. ¶ See appropriate CLEAPSS Hazcard and Recipe Card. A 50 cm3 bottle, with the required hazard label, should be sufficient for each group. ¶* See appropriate CLEAPSS Hazcard and Recipe Card. A 30 cm3 bottle, with the required hazard label, should be sufficient for each group. ¶ Supply either measuring cylinder or pipettes and fillers, depending on availability and the abilities of the students. Equipment

Method 2 ­ Acid and base: copper sulphate* Beaker (250 cm3 Pyrex or equivalent) 40 2

Quantity/group

Petri dish (a clean used petri dish would be suitable) Spatula

Pupil's Book C Chapter 2

Stirring rod Universal Indicator paper¶* Forceps Eye protection Label/marker pen Experimental notes

1 2­3 1 1/student 1

¶*

Provide half size pieces of indicator paper from a booklet in a small plastic pot with the relevant colour chart.

Activity 2.3b

Equipment

Beakers (100 cm Pyrex or equivalent) Bunsen burner, bench mat Copper foil (Provide 6 small pieces of foil in a labelled dish) Hydrochloric acid 0.5M* Iron filings

3

Quantity/group

8 1 1 1 1 ribbon 1 1 1 0.5M¶ 1 1 1/student 1

* See the relevant CLEAPSS Hazcard for disposal of the product of the experiment. See appropriate CLEAPSS Hazcard. Supply a small amount in a labelled container with the required hazard label. Supply either measuring cylinder or pipettes and fillers, depending on availability and the abilities of the students. ¶ See appropriate CLEAPSS Hazcard and Recipe Card. A 100 cm3 bottle, with the required hazard label, should be sufficient for each group. ¶* Provide half size pieces of indicator paper from a booklet in a small plastic pot with the relevant colour chart. Equipment

Method 4 ­ Acid and metal: zinc chloride* Balance (weighing to a minimum of 1g accuracy) Beaker (250 cm3 Pyrex or equivalent) Bunsen burner, tripod, gauze, bench mat Filter funnel (glass or plastic) Filter paper (student grade would be suitable) Granulated (Flammable) zinc 1 0.5M 1 1 (25 cm3 glass 1 1 1 1 1/student paper¶* 2­3 pieces 1 1 3­4/class 1­2 1 1 1

Magnesium (Highly flammable) Matches Spills Sulphuric acid (Irritant)

Quantity/group

Labels/marker pen Eye protection Zinc foil¶* (Flammable)

Experimental notes

Hydrochloric acid Matches

Measuring cylinder or plastic)¶

* See appropriate CLEAPSS Hazcard and Recipe Card. A 100 cm3 bottle, with the required hazard label, should be sufficient for each group. See appropriate CLEAPSS Hazcard. Supply a small amount in a labelled container with the required hazard label. See appropriate CLEAPSS Hazcard. Provide 6 small pieces (2 cm long) of ribbon in a labelled container with the required hazard label. ¶ See appropriate CLEAPSS Hazcard and Recipe Card. A 100 cm3 bottle, with the required hazard label, should be sufficient for each group. ¶ * See appropriate CLEAPSS Hazcard. Provide 6 small pieces of foil in a labelled dish.

Advice on investigation

Pipette (25 cm3 graduated or bulb)¶ Pipette filler (bulb or pi-pump, whichever is available)¶ Petri dish (A clean used Petri dish would be suitable) Eye protection Universal Indicator Label/marker pen Forceps Experimental notes

See the relevant CLEAPSS Hazcard for disposal of the product of the experiment.

Answers

1 Each sentence should have a different meaning of the word base e.g. we made Base Camp 3000 feet up the mountain. 2 Alkalis are chemical bases that are soluble. 3 A metal oxide becomes a hydroxide when it dissolves. 4 A metal is not a base because it does not produce water when it reacts. 5 Hydrogen 6 A test tube of the gas burns with a squeak. 7 Nothing. Gold does not react with acid. 8 The Coke would remove the rust from the iron, leaving it clean. 9 Limescale is a base. 10 Carbon dioxide

* See the relevant CLEAPSS Hazcard for disposal of the product of the experiment. See appropriate CLEAPSS Hazcard. Supply a small amount in a labelled container with the required hazard label. See appropriate CLEAPSS Hazcard and Recipe Card. A 100 cm3 bottle, with the required hazard label, should be sufficient for each group. ¶ Supply either measuring cylinder or pipettes and fillers, depending on the ability of the students and availability.

Match to

National Curriculum references

3.1 f, 3.2 g, 3.3 a, d, e, g

41

Chapter 2

Activity sheet

2.3a Making salts I

Most salts can be made in different ways. There are four basic methods: Acid Acid Acid Acid alkali indicator insoluble base carbonate metal

Choose one of the methods described below and use it to make a sample of a salt. Let the salt solution dry out and crystallise in a petri dish. Write a report on making your particular salt. Include: an account of what you did descriptions of all the changes you saw happen a drawing of what the final crystals looked like When they are dry, pick up some of the crystals on a piece of sellotape and stick them into your report

Methods

1 Acid/alkali method: potassium chloride Take 25 cm3 of dilute potassium hydroxide solution. Add 8 drops of Universal Indicator. Add enough hydrochloric acid until the mixture just goes the acid colour (red/orange). Add drops of acid or hydroxide until the indicator is yellow-green (neutral).

Red/orange/yellow Green/blue Yellow/green Add hydroxide drops Add acid drops Do nothing ­ neutral

Note: It may take a few seconds for the colour of the indicator to stabilise. The mixture now contains the salt, excess water and the Universal Indicator. Add 1 spatula of saturated charcoal. Bring the mixture to the boil and filter when cool enough (the charcoal absorbs the indicator). Boil the colourless solution to reduce the bulk to less than 25 cm3. Put it in a petri dish and leave it in a warm place to evaporate.

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Chapter 2

Activity sheet

2.3a Making salts II

2 Acid and base: copper sulphate Measure out 25 cm3 of sulphuric acid. Add 3 spatulas (an excess) of black copper oxide. Warm the mixture but do NOT let it boil. Allow it to cool and filter off the excess copper oxide. Reduce the volume of the solution by boiling half of it away. Put the remaining solution in a petri dish and allow it to evaporate so crystals will form. 3 Acid and carbonate: magnesium nitrate Measure out 25 cm3 of dilute nitric acid. Add one spatula of magnesium carbonate powder. Let the fizz reaction subside and stir it well. Add another spatula of magnesium carbonate and stir until the fizz subsides. Keep on adding magnesium carbonate until there is no more fizz. Then leave the beaker to stand for 5 minutes more. Stir it every minute or so. Filter off the excess magnesium carbonate. Test the solution with Universal Indicator paper to see if it is neutral. Reduce the volume of the solution by boiling away half the solvent. Put the remaining solution in a petri dish and allow it to crystallise. 4 Acid and metal: zinc chloride Measure out 25 cm3 of hydrochloric acid. Put 10 g of granulated zinc into it. Leave overnight at least. When there are no more bubbles of hydrogen being produced, test the liquid with Universal Indicator paper. If the liquid is neutral, decant or filter off the solution. If the liquid is not neutral, warm the solution to speed up the reaction. Then test the solution again. Reduce the volume of the solution by half by boiling. Evaporate the rest of the water in a petri dish. Allow the crystals to dry completely.

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Chapter 2

Activity sheet

2.3b Metal plus acid

Do all metals get corroded by acids?

So try this

Take a piece of metal and draw or write about what it looks like at the start of the investigation. Place the piece of metal in the acid solution. Draw or write about what the metal looks like in the acid. Draw or write about the metal again after any reaction has happened. If you can, test the gas given off. Ask your teacher if you're not sure what to do.

Results Zinc foil Hydrochloric acid Before Sulphuric acid Before

While in the acid

While in the acid

Afterwards

Afterwards

Magnesium ribbon

Before

Before

While in the acid

While in the acid

Afterwards

Afterwards

Iron filings

Before

Before

While in the acid

While in the acid

Afterwards

Afterwards

Copper foil

Before

Before

While in the acid

While in the acid

Afterwards

Afterwards

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Chapter 2

Homework sheet

2.3 Reactions with hydrochloric acid

There are four common types of reactions with acids: A B C D acid acid acid acid alkali solution salt water basic oxide salt water carbonate salt water carbon dioxide reactive metal salt hydrogen

All the substances in the table below react with hydrochloric acid to make a substance called a salt.

Questions

1 Copy and complete the table for each of the substances. 2 a) Write word equations for each of the reactions. b) Write balanced symbol equations for each of the reactions.

Formula Name of Name of of substance salt substance produced NaOH Sodium hydroxide Are water Are Are CO2 Is an molecules hydrogen molecules indicator produced? molecules produced? needed? produced? Is it reaction type A, B C or D

CuO

Zn

KOH

CaO

Calcium Oxide

Li2CO3

Magnesium metal

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45

Pupil's Book C Chapter 2

2.4 Metal and non-metal oxides

Rationale

All elements that react will combine with oxygen. This spread introduces a series of elements from Period 3 of the Periodic Table and examines how they react differently with oxygen. Remind pupils of the reaction between iron/sulphur or magnesium/sulphur to confirm this idea.

Suggestions

Literacy

Consolidate the terms sulphide, oxide, chloride and nitride as names of binary compounds. There are many spectacular reactions in this chapter. At some time, introduce the difference between adjectives which are emotive (fantastic, spectacular) and scientific (corrosive, dangerous, flaring).

Learning outcomes

Most pupils will learn: how to test for oxygen gas that metals and non-metals both produce oxides that some oxides of metals dissolve in water to make alkalis that all oxides of metals are bases that some oxides of non-metals dissolve in water to make acids. The faster pupils will learn: how to make oxygen gas that not all acids are non-metal oxides that only the most reactive metals produce oxides that are alkalis. Those who learn less quickly will know that oxides produce solutions of different pH.

ICT

Use CD-ROMs and the Internet to survey reactions of metals and non-metals. Use Chemistry Set 2000 from New Media to see videos of direct reactions between metals and non-metals.

Sc1 Ideas and evidence

Activity Sheet 2.4 can be structured as an investigation to identify a pattern of reactivity in materials.

Cover friendly rating

0 stars (activity ­ involves hazardous substances); 4 star (textbook): 4 star (Homework)

Lesson plan

1 hour/lesson

Suggested starter

Cross curricular links

D&T (corrosion of metals)

On the bottom of page 23 in Pupil's Book C there is a description of making a small amount of oxygen and testing it. The test is that the oxygen gas will re-kindle a glowing wood splint. Use this as a class activity to give a focused start to the lesson.

Main activity

Technician's notes

Demonstration

Equipment

Bunsen burner, bench mat Charcoal* Deflagrating spoons Gas jars of Iron wool oxygen

Quantity/group

1 1 1 for each sample 1 for each sample 1 1 1 1

Demonstrate the burning of different elements in oxygen. Collect several gas jars of oxygen. Make sure there is 5 or 6 cm of water left in the jar. Burn, for example, sodium metal, magnesium ribbon, iron wool, carbon (charcoal) and sulphur on deflagrating spoons in the gas. Pupils and teacher should wear eye protection throughout. Ensure pupils do not look directly at the magnesium burning. For the sodium demonstration, use safety screens and only a very small piece of sodium. After cooling, add plenty of water to remove the oxide which coats unreacted sodium. When sulphur is burned, sulphur dioxide is produced, so a fume cupboard may be required. Make observations to contrast burning in the air and burning in pure oxygen. Then shake the gas jars to dissolve the oxides and add Universal Indicator solution. Use the colours of the indicator to classify the oxides as acidic, alkaline or neutral. Activity 2.4 All the same?: Use this as a class investigation into the similarities in the reactions of acids.

Suggested finisher

Magnesium ribbon¶ (Highly flammable) Matches Safety screens Sodium metal¶* (Highly flammable/ Corrosive) Scalpel, forceps, white tile (for use with sodium metal (Highly flammable/Corrosive)) Sulphur (Flammable) Universal Indicator solution¶ (Highly flammable) Eye protection or face shield

1

1 1

Work through Spread 2.4 of Pupil's Book C. Ask the pupils to answer the questions and complete the remember box.

Homework

Homework 2.4 Oxides, sulphides and nitrides: This consolidates the ideas about binary compounds produced by reactions between metals and non-metals.

46

1 1

Pupil's Book C Chapter 2

Experimental notes

* Supply a small amount in a labelled container with the required hazard label. See appropriate CLEAPSS Hazcards and Recipe Card to make the oxygen. See appropriate CLEAPSS Hazcard. Supply a small amount in a labelled container with the required hazard label. ¶ See appropriate CLEAPSS Hazcard. Provide small pieces of ribbon in a labelled dish with the required hazard label. ¶ * See appropriate CLEAPSS Hazcard. Supply in its original container. Ensure that all pieces of these metals have been returned to their correct containers before putting the equipment for washing. ¶ See appropriate CLEAPSS Hazcard and Recipe Card. A 30 cm3 bottle, with the required hazard label, should be sufficient.

Advice on investigation

Test tube holder Test tube rack Universal Indicator (Highly flammable) Limewater Experimental notes solution¶

1 1 1 1

See the relevant CLEAPSS Hazcard for disposal of the product of the experiment.

Class practical

Equipment

Beaker (100 cm3 Pyrex or equivalent) Bunsen burner, tripod, gauze, bench mat Clock Copper(II) oxide powder* (Harmful) Ethanoic acid 1M Eye protection Hydrochloric acid 0.5M Labels/marker pens

Quantity/group

6 1 1 1 1 1/student 1 1

* See appropriate CLEAPSS Hazcard. Supply a small amount in a labelled container with the required hazard label. See appropriate CLEAPSS Hazcard and Recipe Card. A 50 cm3 bottle, with the required hazard label, should be sufficient for each group. See appropriate CLEAPSS Hazcard. Provide 8 (2 cm) pieces of ribbon in a labelled container with the required hazard label. ¶ See appropriate CLEAPSS Hazcard. A 100 cm3 bottle, with the required hazard label, should be sufficient for each group. To make 0.5M phosphoric acid solution: 33 cm3 conc. phosphoric acid, 967 cm3 water. Follow the procedure for making sulphuric acid on appropriate CLEAPSS Recipe Card (Reference: Creedy A Laboratory Manual for Schools and Colleges, HEB Published 1977 p. 68) ¶* Use appropriate CLEAPSS Recipe Card. A 100 cm3 bottle should be sufficient for each group. ¶ See appropriate CLEAPSS Hazcard and Recipe Card. A 100 cm3 bottle, with the required hazard label, should be sufficient for each group. ¶ See appropriate CLEAPSS Hazcard and Recipe Card. A 30 cm3 bottle, with the required hazard label, should be sufficient for each group.

Advice on investigation

See the relevant CLEAPSS Hazcard for disposal of the product of the experiment.

Answers

1 2 3 4 5 6 7 8 9 10 Metals are shiny and conduct electricity. Non-metals look dull and do not conduct electricity. Because sodium reacts quickly with air. Caustic soda The symbol is orange and shows a hand being eaten away by a chemical. Oxygen Indicator paper will go red Non-metal oxides are acidic Metal oxides are bases Potassium manganate(VII) crystals give off oxygen when heated.

Magnesium carbonate powder* 1 Magnesium (Highly flammable) Matches Measuring cylinder (100 cm3 glass or plastic) Pipette (5 cm3 or 10 cm3 graduated) Pipette filler (bulb or pi-pump, whichever is available) Phosphoric acid 0.5M¶ (Irritant) Salt water 1M¶* Spatula Spill Sulphuric acid (Irritant) 0.5M¶ 1 ribbon 1 1 1 1 1 1 1 2 1

Match to

National Curriculum references

3.1 c, e, 3.3 a, d, e, g, h

Test tube (medium- or heavy-walled, Pyrex or equivalent)

8 47

Chapter 2

Activity sheet

2.4 All the same? I

1

2

3 Universal Indicator

colour?

Waft the tube towards your nose. But DON'T put your nose over the test tube

colour?

magnesium ribbon 4 5

magnesium carbonate 6 7

Pour the gas into the lime water and shake

after 5 minutes

lime water

copper oxide

You are going to carry out some tests on six different liquids to see how they react.

So try this

Wear eye protection. Take a small (100 cm3) beaker of each of the six liquids in turn. Try the seven tests on each liquid and record the results on the page your teacher will give you. Use fresh solution for each test (except test 7 which uses the solution from test 6). If you don't get all the liquids tested, share results with your neighbouring groups. Which reactions are the same for all the acids? Do other liquids show these `acid' reactions?

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Chapter 2

Activity sheet

2.4 All the same II?

2 in size)

Salt water

Results table part 1 (Photocopy onto A3 paper,

Test 1 What colour is the liquid? 2 What does the liquid smell of? 3 Add 2 drops of Universal Indicator solution to the liquid. What do you see? 4 Add a small (2 cm) piece of magnesium ribbon to the liquid. What happens? 5 Add 1 spatula of copper(II) oxide powder. Warm the test tube and leave it to stand for 5 mins. What do you see? 6 Add 1 spatula of magnesium carbonate to the acid. What do you see? 7 Test the gas given off to see if it is carbon dioxide. Ethanoic acid Hydrochloric acid

Results table part 2

Test 1 What colour is the liquid? 2 What does the liquid smell of? 3 Add 2 drops of Universal Indicator solution to the liquid. What do you see? 4 Add a small (2 cm) piece of magnesium ribbon to the liquid. What happens? 5 Add 1 spatula of copper(II) oxide powder. Warm the test tube and leave it to stand for 5 mins. What do you see? 6 Add 1 spatula of magnesium carbonate to the acid. What do you see? 7 Test the gas given off to see if it is carbon dioxide. Tap water Sulphuric acid Phosphoric acid

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Chapter 2

Homework sheet

2.4 Oxides, sulphides and nitrides

Magnesium is quite a reactive metal. It will burn in air to make a white powder. This white tongs powder is heavier than the magnesium metal that was magnesium ribbon giving burned. The white powder is off white smoke and fumes magnesium oxide. Hot burning magnesium will also react with the nitrogen in the air. The nitrogen particles get pulled apart by the high temperatures of the oxidation reaction. The nitrogen molecules get turned into nitrogen atoms and these react with the magnesium as well. A new substance called magnesium nitride is made. Magnesium nitride has the formula of Mg3N2. The magnesium has combined directly with the nitrogen, with no other elements involved. This is why it is called a nitride. If it is left, magnesium nitride will slowly react with oxygen in the air to make magnesium oxide. You can't see any change because both compounds are white powders. Magnesium sulphide is made by direct combination of the two elements magnesium and sulphur. But take great care, as it is a reaction that gives off lots of energy. A mixture of magnesium and sulphur is put in a heat resistant (Pyrex) test tube. This is heated in a Bunsen flame. The sulphur melts and becomes a brown, sticky liquid. Soon the reaction starts and a red glow spreads right through the mixture. The whole reacting mixture gets red hot and gives off fumes, so the reaction has to be done in a fume cupboard. After the mixture has cooled, the magnesium sulphide is a solid lump. The test tube has to be broken to get it out. It looks like a hard, dark grey solid, quite different from magnesium or sulphur. The magnesium sulphide can be identified by adding some dilute hydrochloric acid to it. But this test must be done in a fume cupboard as well. The reaction gives off a gas called hydrogen sulphide which smells like bad eggs. It is the gas produced by `stink bombs'. People should be very careful because the gas is quite poisonous. However the smell drives normal people away before enough gas builds up to cause much harm. Hydrogen sulphide is the smell in human flatulence and is added to the natural gas supply to make leaks easier to detect.

Questions

1 Make a list of the 10 words in the passage that are underlined. Next to each word, write an explanation of what it means. 2 Nitrogen gas is normally quite unreactive. Why does it react with magnesium? 3 Write a word equation for magnesium reacting with nitrogen. 4 The formula of magnesium nitride is Mg3N2. What does this mean? 5 What colour is magnesium nitride? 6 What can be seen to happen when magnesium sulphide is made? 7 Why must the reaction be done in a fume cupboard? 8 How can you test the substance produced in the reaction, to show a change has taken place? 9 What is the name of the smelly gas produced? 10 Why is this gas dangerous? 11 Write a word equation for making this gas from magnesium sulphide. 12 What can this gas be used for?

50 Hodder Science Teacher's Resource C © 2003 Hodder & Stoughton Educational

Pupil's Book C Chapter 2

2.5 Metals

Rationale

Chapter 2 of Hodder Science Pupil's Book C covers both Units 9E and 9F of the QCA Scheme of Work. This is to make some space in a very crowded Year 9 programme to complete all the units of the Scheme of Work. Spreads C2.5 to C2.8 cover Unit 9. 2.5 Rusting can be adapted to become a practical activity and a series of prompts.

Suggested finisher

Finisher E Metal discovery: This may take more time than is available at the end of a practical lesson, so it could be finished as a homework task.

Homework

Learning outcomes

Most pupils will: learn that metals are obtained from rocks from the Earth's surface learn that one or two unreactive metals are found uncombined in the Earth's crust recognise the blast furnace as the apparatus for making iron from iron ore. The faster pupils will: learn that the blast furnace involves high temperatures and carbon monoxide gas find out that making aluminium metal involves using electricity to separate aluminium from oxygen in bauxite. Those who learn less quickly will learn that: metals do not occur naturally and that their manufacture involves chemical changes many metals have only been discovered recently.

Homework 2.5 Rusting: Consolidates pupil's knowledge of the causes and prevention of rust.

Suggestions

Literacy

There are many stories about men seeking metals, usually gold. Find accounts of the 1849 California Gold Rush and the later Yukon gold fields. Use these for stimulus material. Ask pupils why the only metals whose normal sources are being found uncombined in the Earth's surface are gold and silver.

Numeracy

Draw a time line for the discovery of metals. Look up the cost of different metals on the commodity exchange. Use data of gold price fluctuations over the years to plot as a graph. Find out what determines the price of gold bullion.

Lesson plan

1 hour/lesson

Suggested starter

ICT

Use CD-ROMs such as Microsoft Encarta and other CD-ROM encyclopaedias to find out more about the origins and discovery of metals. Make a PowerPoint presentation about the discovery of metals.

As a starter activity get the class to read the lighthearted Spread 2.5 in Pupil's Book C. Omit the section on the blast furnace and concentrate on the history of the discovery of metals.

Main activity

Cover friendly rating

0 stars (activity ­ involves heating); 4 star (textbook); 3 star (Homework)

Making metals can be introduced by a practical demonstration. 1 Reduce copper oxide to copper metal by heating it strongly while passing methane over it. Before heating, ensure all air has been displaced. To do this, collect samples of the gas in a test tube and ignite at least one metre away (until it burns quietly). Burn off the excess methane as a jet at the end of the apparatus. Show that black copper oxide turns into a red-brown powder that conducts electricity. 2 Demonstrate the reduction of lead oxide to lead metal using a charcoal block and a blow pipe. Your risk assessment for this activity may consider that while it is hazardous (toxic lead fumes) as a class activity, it is acceptable at the much lower exposure rate of a demonstration. A demonstration also has the advantages of ensuring success and correct observations. The demonstration can be carried out in a fume cupboard. Activity 2.5 Early metal discovery: This is a less spectacular version of the same thing. Make sure it is carried out in a well-ventilated room. Rusting experiments may have been carried out in previous years. If they have not been done, this section could be a good opportunity. Homework

Cross curricular links

D&T (properties of metals), Geography (sources of metal ores)

Technician's notes

Demonstration 1

Equipment

Copper oxide powder (black)* (Harmful) Eye protection/face Safety screens Combustion tube Bunsen burner, bench mat Matches Rubber tubing hole) shield

Quantity/group

1 1 1 1 1 1 1 1 continued 51

Rubber bung (one

Pupil's Book C Chapter 2

Equipment

continued Glass tubing

Quantity/group

Class activity

Equipment Quantity/group

1 1 1 oxide 1 1 1 1 1 1/student Bunsen burner, bench mat Charcoal powder*

1

ELECTRICITY Batteries (1.5V) Battery holder Bulb holder and bulb (Either 1.5V or 1.25V) Crocodile clips/4mm plug leads (depending on type of battery holders available) Experimental notes 1 1 1

Clock Lead (Toxic)

Retort stand, boss head and clamp Test tube (medium- or heavywalled Pyrex or equivalent)

3

Tin lid Wooden spill Eye protection Experimental notes

* See appropriate CLEAPSS Hazcard. Supply a small amount in a labelled container with the required hazard label. Pupils should wear eye protection during the demonstration. The teacher should also be protected with a face shield. Supply sufficient rubber tubing to connect to the gas supply and to the combustion tube. Using a rubber bung with one hole, insert a 10 cm length of medium wall glass tubing in to it, following the method described in CLEAPSS Laboratory Handbook. Ensure that the ends of the glass tubing have been flame polished.

Advice on investigation

* Supply a small amount in a labelled container with the required hazard label. Provide to the ratio 3:1 charcoal:lead oxide (Toxic). See appropriate CLEAPSS Hazcard. Supply a small amount in a labelled container with the required hazard label. Provide to the ratio 3:1 charcoal:lead oxide (Toxic).

Advice on investigation

Ensure room is well ventilated. See the relevant CLEAPSS Hazcard for disposal of the product of the experiment.

See the relevant CLEAPSS Hazcard for disposal of the product of the experiment.

Answers

1 2 3 4 5 6 7 8 9 10 11 12 Gold In rocks on the Earth's surface Making hot fires surrounded by stones The least reactive metals were discovered first Carbon Iron needed higher temperatures to be made Aluminium By using electricity Blast furnace Limestone A blast of air blowing through coke Iron oxide carbon iron carbon dioxide

Demonstration 2

Equipment

Lead oxide* (Toxic) Charcoal block

Quantity/group

1 1 1 1 1 1/student

Blow pipe Bunsen burner, bench mat Matches Eye protection Experimental notes

Match to

National Curriculum references

3.1 c, 3.1 f, 3.3 a, h

* See appropriate CLEAPSS Hazcard. Supply a small amount in a labelled container with the required hazard label. Ensure that the charcoal block is fully extinguished before putting away in a metal box.

Advice on investigation

See the relevant CLEAPSS Hazcard for disposal of the product of the experiment.

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Chapter 2

Activity sheet

2.5 Early metal discovery

It has long been thought that the earliest discovery of metal was serendipity. Serendipity means a chance happening that brings benefits ­ like finding a valuable fossil when you're not hunting for them. It is thought that ancient people built fires with rocks round to keep the fire under control and that the rocks sometimes contained metal ores. These metal ores reacted with the chemicals in the fire to produce metals.

So try this

You are going to test this idea by using the apparatus below and following the instructions given.

heat-resistant test tube

wooden splint clamp stand charcoal and lead oxide mixture

Bunsen burner

heat-proof mat

Place the mixture of charcoal and lead oxide (in the ratio 3 parts charcoal: 1 part lead oxide) in a heat-resistant test tube. Clamp the test tube in a stand on a heat-proof mat, like in the diagram above. Heat the mixture very strongly with a roaring blue Bunsen flame. Stir the mixture from time to time with a wooden splint. After heating and stirring for 10 minutes, pour the mixture out onto a tin lid. Observe it closely for any changes, and particularly for any shiny blobs of metal.

Make a record

Write your own account of this experiment. Use the headings `What we used', `What we did', and `What we saw'.

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53

Chapter 2

Homework sheet

2.5 Rusting

Activity 1

Tube 1 Tube 2 Tube 3 Tube 4

oil boiled water boiled water

water

anhydrous calcium chloride to remove moisture from the air

Tube 1: Nail has rusted because oxygen and water are present. Tube 2: Nail has been kept dry, so no rusting took place. Tube 3: Nail is in boiled water that has no oxygen in it, but oxygen has dissolved into the water, so the nail slowly rusts. Tube 4: Nail is in boiled water, and the surface of the water is sealed from the air by a layer of oil ­ no rusting takes place due to the absence of oxygen.

Questions

1 2 3 4 5 Why does boiled water have no oxygen in it? Why does the nail in tube 2 not go rusty? Why does the nail in tube 3 eventually go rusty? What is rust? Why does it flake away from metal surfaces? If an iron or steel object is deep at the bottom of a very cold ocean, it rusts slowly. Explain why this could be. (Hint: Test tube 4) 6 What two materials combined are necessary to cause rusting? 7 Write a paragraph about the best way to keep tools free of rust in a slightly damp garage or shed.

Activity 2

Look at the table below about rust treatments. Evaluate the effectiveness of the rust treatments. Say which would be best, and explain the different results as fully as you can.

Treatment 1 Paint over the rust Result Surface looked good, but after several weeks the rust bubbled and split the paint surface. The result was even worse. Removed most of the rust, but some was still left in the pits and holes caused by previous rusting. This produced centres for rusting to start again ­ but slowly. The phosphoric acid dissolved away all the rust, leaving a fresh metal surface with no corrosion. As long as the surface was kept dry, no further corrosion took place. The rusted surface became even more corroded. Rust began to flake and hold the water. Soon the metal was rusted right through.

2 Wire brush the rust off the surface

3 Treat with dilute phosphoric acid and rinse off 4 Treat with salt water

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Hodder Science Teacher's Resource C © 2003 Hodder & Stoughton Educational

Pupil's Book C Chapter 2

2.6 Treasure

Rationale

This spread starts to introduce ideas about the reactivity series. The concept is put in the context of a chest of treasure that has been exposed to sea water for nearly 200 years. All the valuable and crafted metal objects have corroded according to their reactivity. Aluminium metal has an inert coating that renders it immune to corrosion by air, but sea water will dissolve this coating and the metal will corrode rapidly. Aluminium was first used as a material during Napoleonic times. It was rare and expensive. This activity is quite a lengthy piece of work and may take up the rest of the lesson, including the plenary session. One way to reduce the time is to get different groups of pupils to perform the three stages of the cycle, like in a production line. Stage 1 passes their product (copper oxide) to Stage 2. Stage 2 passes copper sulphate solution to Stage 3. Stage 3 produces copper metal. This activity has been used as an `open evening' pupil demonstration very effectively.

Suggested finisher

Learning outcomes

Most pupils will: learn about the reactivity series of metals learn that the differences in rates of reactivity apply equally to reactions with air, water and acids identify patterns of similar chemical reactions for various metals explain the uses of metals in the context of the reactivity series. The faster pupils will: be able to make predictions about the reactions of metals from a knowledge of the reactivity series construct a reactivity series from observed data. Those who learn less quickly will know that: metals corrode differently corrosion happens when metals are exposed to air and water.

If time from the practical activity permits, finish the drawing started from the treasure story in the starter activity above.

Homework

Homework 2.6 Metals A­Z quiz: A quick A­Z quiz about metals.

Suggestions

Literacy

There are lots of treasure stories and shipwreck stories in both fiction and journalism that give accurate information about the corrosion of metals. Let pupils invent their own crime stories, where forensic evidence about corrosion leads to information about the crime. Encourage the imagination: get pupils to describe the colour and patina of metal objects e.g. an old gold necklace, silver in a jeweller's window, a rusty bicycle, the well-worn and shiny patina of the steel stair edges in an Underground station, a new steel hinge etc.

Lesson plan

1 hour/lesson

Suggested starter

ICT

Read the class the treasure story from Spread 2.6 of Pupil's Book C. Try to perform it in as animated a way as possible. Don't show them the book spread yet! Ask the pupils to draw the contents of the treasure chest, both before (when it was first brought back) and after (when it had corroded). The chest contains gold ornaments, silver helmets, copper goblets, thin iron daggers and a sword with fine handles, and aluminium plates that completely corroded to powder.

Main activities

Find out about corrosion from CD-ROMs and the Internet. Search the Internet for treasure stories.

Sc1 Ideas and evidence

Set up an investigation to do one of the following: 1 Investigate the amount of corrosion on a steel nail in different conditions 2 Compare different rust removers to see which is the most effective 3 Investigate how much rust (iron oxide) will dissolve in different strengths of phosphoric acid solution. (Measure strength in grams per litre.)

If they have not done the starter, get the pupils to read the textbook spread. Use this as an introduction and stimulus for a discussion about the reactivities of metals. Remind pupils of their work on rusting and the factors that affect the rate of rusting. Relate this to the idea of a `fair test' for corrosion. Get pupils to survey the locality, looking for metal objects and fittings. Relate the condition of these objects to age, exposure, conditions, protection from corrosion and type of material. Collate the pupils' findings and look for patterns. Activity 2.6 Copper cycle: Use this as either a class practical or get pupils to do only part of the activity to make it quicker. The activity is in three stages ­ heating, dissolving and electrolysis.

Cover friendly rating

0 stars (activity ­ involves heating and hazardous substances); 4 star (textbook); 4 star (Homework)

Cross curricular links

English (creative writing of treasure stories), D&T (use of metals)

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Pupil's Book C Chapter 2

Technician's notes

Stage 1

Equipment

Bunsen burner, bench mat Copper carbonate* (Harmful) Eye protection Lime water Test tube (medium- or heavywalled Pyrex or equivalent) Rubber bung (1 hole ­ to fit test tube) Tongs Spatula Boiling tube Trough Beehive shelf Delivery tube Test tube rack (to take both the test tube and the boiling tube) Eye protection Experimental notes

Experimental notes

Quantity/group

1 1 1/student 1 1 1 1 1 1 1 1 1 1 1/student

* See appropriate CLEAPSS Hazcard. Have available, if insufficient has been produced in Stage 1, a small amount in a labelled container with the required hazard label. See appropriate CLEAPSS Hazcard and Recipe Card. A 50 cm3 bottle, with the required hazard label, should be sufficient for each group. 10°C to 110°C, 150 mm non-toxic fill, fitted with an anti roll device. A suitable anti roll device for a thermometer is the plastic packaging tip. If very accurate measurements are required, mercury filled thermometers should be used.

Stage 3

Equipment

Solution from stage 2 Copper sulphate solution (0.5 M)* (Harmful) Ammeter Carbon electrodes Clock Eye protection Low voltage power supply Experimental notes

Quantity/group

1 1 1 1 1/student 1

* See appropriate CLEAPSS Hazcard. Supply a small amount in a labelled container with the required hazard label. Avoid raising dusts. See appropriate CLEAPSS Hazcard and Recipe Card. A 100 cm3 bottle, with the required hazard label, should be sufficient for each group.

* See appropriate CLEAPSS Hazcard and Recipe Card. Have available, if insufficient has been produced in Stage 2, a 50 cm3 labelled bottle, with the required hazard label.

Advice on investigation

See the relevant CLEAPSS Hazcards for the disposal of the products of the reactions.

Stage 2

Equipment

Beaker (50 cm3 Pyrex or equivalent) Bunsen burner, tripod, gauze, bench mat Product of Stage 1 Copper(II) oxide* (Harmful) Filter funnel (glass or plastic) Filter paper (student grade would be suitable) Eye protection Stirring rod (glass) Sulphuric acid 1M (Irritant) Balance (weighing to an accuracy of a minimum of 1 g) Measuring cylinder (25 cm3 glass or plastic) Thermometer

Answers

Quantity/group

2 1

1 1

1 Gold, silver, iron, copper, aluminium 2 Gold 3 Aluminium 4 aluminium most reactive iron copper silver gold least reactive 5 The plates and the daggers 6 Corrosion

Match to

1 1/student 1 1 3­4 1 1

National Curriculum references

3.1 d, 3.3 a, c, h

56

Chapter 2

Activity sheet

2.6 Copper cycle I

Copper is a fairly unreactive metal, but it still reacts steadily with oxygen in the environment. All the copper in the Earth's crust is found as copper compounds. One rock that is a big source of copper metal is a green rock called malachite. You can turn malachite into copper metal in the laboratory. Your task is to carry out this three-stage process, and to accurately describe the changes at each stage.

Stage 1: turning malachite into copper oxide

Explanation

Malachite contains a great deal of copper carbonate. Many carbonate compounds will fall apart when you heat them, in a process called thermal decomposition. This is the word equation for the reaction: copper carbonate

Method

HEAT

copper oxide

carbon dioxide

Put three or four spatulas of copper carbonate in a heat-resistant test tube. Heat the tube over a blue Bunsen flame and observe the colour change. Collect the gas given off. Carry on heating the copper carbonate until no more gas is given off. Test the gas you have collected with lime water and write down what you see. Write a complete account of what you did, using the headings `What we used,' `What we did', and `What we saw'.

Stage 2: making copper oxide into copper sulphate solution

Explanation

Copper oxide is a base. It will dissolve in an acid to make a neutral solution. The neutral solution contains a copper salt corresponding to the acid. The word equation for the reaction between copper oxide and sulphuric acid is: copper oxide

Method

sulphuric acid copper sulphate solution

Take at least 2 g of copper oxide powder. Put it in a 50 cm3 beaker and add 10 cm3 of 1M sulphuric acid. Heat the mixture and stir with a glass rod. DO NOT heat the mixture to boiling ­ stop heating at 70°C. Stir the mixture as it cools. Filter off the unreacted copper oxide. Put the copper sulphate solution into a 50 cm3 beaker for Stage 3. Write down what you used, what you did and what you saw happen.

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57

Chapter 2

Activity sheet

2.6 Copper cycle II

Stage 3: getting copper from copper sulphate solution

Explanation

Compounds can be broken up using electricity. The energy put into the compound will often reverse a previous chemical change. This process is called electrolysis. When copper sulphate is electrolysed, it produces copper metal, sulphuric acid and oxygen gas.

low voltage supply set to 5V DC

+ ­

digital ammeter

crocodile clips

+

carbon electrode

­

copper sulphate solution

The word equation for the electrolysis reaction is: copper sulphate

Method

water copper metal

sulphuric acid

oxygen gas

Place carbon electrodes in the solution (from Stage 2), and attach them to an ammeter and a low voltage DC supply (see diagram). Switch on the low voltage supply and adjust the voltage to give a current of about 0.5 amps. Pass this current through the solution for 5 minutes. Observe the solution and write a sentence about any changes. Remove the electrodes and look for changes in them. Write down what you used, what you did and what you saw.

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Hodder Science Teacher's Resource C © 2003 Hodder & Stoughton Educational

Chapter 2

Homework sheet

2.6 Metals A­Z quiz

When you have worked out all the answers for this A­Z quiz, make up your own questions for another A­Z quiz. A ­ A mixture of metals. B ­ A substance that neutralises an acid. C ­ Reacts with water to give a white, alkaline solid. D ­ When one metal kicks another out of a compound or solution. E ­ A collection of identical atoms. F ­ This is the symbol for iron. G ­ This will stop the moving parts of a bicycle from going rusty. H ­ Magnesium is ___________ in the reactivity series than zinc. I ­ A non-metal that forms a brown solution and a purple gas. J ­ Zinc will ___________ displace iron from iron sulphate solution. K ­ What element has this symbol? L ­ Is the least reactive of the alkali metals. M ­ Plus oxygen, it forms a base. N ­ Plus oxygen it forms an acidic oxide. O ­ This reacts with sulphur to make an acid gas. P ­ A non-metal that used to be found in match heads. Q ­ The strongest acid of all has this letter in its name. R ­ This material forms on iron and steel when they corrode. S ­ A metal that melts as it reacts and dissolves in water. T ­ A very strong metal. U ­ A radioactive metal. V ­ Only one element has a name beginning with this letter. Can you name it? W ­ This must be present for rust to form. X ­ Will iron displace magnesium from magnesium nitrate solution? Y ­ Would copper oxide react with magnesium powder? Z ­ There is only one element whose name starts with this letter. What is it?

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Pupil's Book C Chapter 2

2.7 Reactivity to order

Rationale

The alkali metals are known by name and by familiarity with the Periodic Table. But they really are the most astonishing set of elements, particularly because they are metals. Their violent reactions, the fact that oxygen corrodes their surfaces in seconds, their softness and their storage, all make them the stuff of awe and wonder. If we teachers were magicians, we would give the reactions of the alkali metals a wonderful build up. They would be the climax of our art. Due to familiarity, we sell them short as another demo and never give them the star status they deserve. The Open University video clip of rubidium reacting with water must be `top of the pops' for science videos since 1965, but we tend to be prosaic about these wonderfully dangerous metals. very interesting, cheap and technically more challenging approach. The Royal Society for Chemistry has been keen to promote more microscale experiments.

Suggested finisher

Use Spread 2.7 of Pupil's Book C. Work through the questions orally. Pupils should find this straightforward after the practical work.

Homework

Pupils will need homework time to complete accounts of the practical work they have carried out during the lesson.

Suggested starter

Learning outcomes

Most pupils will: learn the names of the alkali metals learn about their reactions with water and air learn why they are stored under oil see the reaction of the alkali metals with water. The faster pupils will: appreciate the trend in reactivity of the alkali metals see that the new, freshly cut surface is shiny see the cut surface of the metal corrode in seconds on exposure to air. Those who learn less quickly will: know that there are some spectacularly reactive metals know that the reactions of some metals with water are so reactive that the hydrogen given off burns know that metals can explode on contact with water.

Starter C Acid, base or neutral?: Consolidates the work done on acids and alkalis earlier. This uses the formulae of compounds so is a good introduction to the main activity.

Main activity

Equations: This lesson has been reserved for whatever basic teaching is needed to cover the topic of symbols and equations. The content is didactic, so the resources and exercises are left for the teacher to decide.

Suggested finisher

Finisher F Symbol bingo: Finish the lesson with a game of bingo, award a prize to the winner.

Homework

Homework 2.7 A metal superstar: A literacy based activity about metals, their properties and activities.

Suggestions Lesson plan

2 hours/lessons

Suggested starter

ICT

The Chemistry Set 2000 CD-ROM by New Media has a full set of clips of all the alkali metals reacting with both air and water. These should be used IN ADDITION to real demonstrations of the reactions of lithium, sodium and potassium. In this way a full experience of all the reactions in a series can be gained. After the initial demo, pupils can play and re-play the video clips until they are really clear about the trend in the reactions.

Demonstrate the reactions of lithium, sodium and potassium with air and water. Take appropriate safety precautions, but there is no substitute for seeing these spectacular reactions in the first person. To extend this to the whole group of alkali metals, use a video of rubidium and caesium to show how the reactions become more and more extreme. An alternative to the video source of data is the Chemistry Set 2000 CD-ROM from New Media. This contains video clips of the reactions of all the alkali metals with oxygen and water.

Main activity

Sc1 Ideas and evidence

These reactions are too hazardous for first-hand data analysis, but the video material about them can provide opportunities for obtaining evidence and analysing evidence.

Use the Chemistry Set 2000 CD-ROM, other sources and the textbook spread, to gain data about the pattern of properties of the alkali metals and the reactivity series. Then confirm the idea of a reactivity series by using Activities 2.7a or 2.7b. Activity 2.7a and 2.7b Taking its place: Both of these are about displacement reactions and a reactivity series for all metals. Activity 2.7b is a microscale approach to these reactions. A microscale approach is particularly appropriate in these cases. It makes a

60

Cover friendly rating

0 stars (both activities ­ involve hazardous materials); 3 star (textbook); 4 star (Homework)

Cross curricular links

D&T (metals)

Pupil's Book C Chapter 2

Technician's notes

Demonstration

Equipment

Glass trough Beaker Lithium metal* (Flammable/Corrosive) Potassium metal* (Highly Flammable/Corrosive) Safety screens Scalpel Sodium metal* (Highly Flammable/Corrosive) White tile Eye protection/face shield Experimental notes

Activity 2.7(II)

Equipment Quantity/group

1 1 1 1 1 1 1 1 1/student Copper foil* Copper sulphate solution (Harmful) Magnesium ribbon (Highly flammable) Magnesium sulphate solution 1M Lead foil Lead sulphate solution 1M (Toxic) Zinc foil Zinc sulphate solution 1M Iron nail (fine ­ cut into 6 small pieces) Iron(II) sulphate solution 1M (ferrous sulphate) (Harmful) Sheet of white card laminated Dropping pipettes (plastic disposable) Forceps (one pair for each metal foil sample) Magnifying lens Eye protection Experimental notes

Quantity/group

1 1M 1 1 1 1 1 1 1 1

* See appropriate CLEAPSS Hazcard. Supply in the original container. Ensure that all pieces of these metals have been returned to their correct containers before putting the equipment for washing. Use no more than the following side lengths of each metal: 5 mm of lithium (carry this reaction out in a beaker), 3 mm of potassium, 4 mm of sodium.

Advice on investigation

1 1 6 4 1 1/student

See the relevant CLEAPSS Hazcards for the disposal of the products of the reactions. Students should wear eye protection if within `firing distance' of the trough. Keep trough close to screens so pieces cannot be ejected over the screen. Never constrain the movement of sodium or potassium on the water in the trough.

Activity 2.7(I)

Equipment

Clock Copper sulphate solution 1M* (Harmful) Iron filings

Quantity/group

1 1 1 1 1­2 1/student

Spatula Test tube (medium- or heavywalled Pyrex or equivalent) Eye protection Experimental notes

* Provide 6 small pieces of foil. Cut the foil into very small pieces and supply in a labelled plastic pot. See appropriate CLEAPSS Hazcard and Recipe Card. A 30 cm3 bottle, with the required hazard label, should be sufficient for each group. See appropriate CLEAPSS Hazcard. Provide 6 small pieces of ribbon. Cut the foil into very small pieces and supply in a labelled plastic pot. ¶ Using an A4 sheet of white card, divide into 12 equal sections using permanent marker pen 3 4. Laminate, if possible. Alternatively cover the whole card using clear book covering.

Advice on investigation

See the relevant CLEAPSS Hazcards for the disposal of the products of the reactions.

Answers

* See appropriate CLEAPSS Hazcard and Recipe Card. A 30 cm3 bottle, with the required hazard label, should be sufficient for each group. See appropriate CLEAPSS Hazcard. Supply a small amount in a labelled container with the required hazard label.

Advice on investigation

See the relevant CLEAPSS Hazcards for the disposal of the products of the reactions.

Titanium is very strong and light. It is resistant to corrosion TiCl4 4Na Ti + 4NaCl To prevent the sodium reacting with air Sodium is more reactive than titanium. To prevent the acid from damaging sea creatures. They react, producing hydrogen which burns, and sometimes they explode 8 Sodium water sodium hydroxide hydrogen 9 The reaction does not get hot enough. 10 caesium most reactive rubidium

61

1 2 3 4 5 6 7

Pupil's Book C Chapter 2

potassium sodium lithium

least reactive

Answers to Finisher F

1 Au, 2 Su, 3 Pb, 4 Hg, 5 Na, 6 N, 7 Ne, 8 Ag, 9 Pt, 10 U, 11 Fe, 12 Cu, 13 NH 4 , 14 CO2 , 15 SO2 , 16 NO 3 , 17 Mg, 3 4 18 Pu, 19 K, 20 W .

Match to

National Curriculum references

3.1 c, d, 3.3 a, b, c, h

62

Chapter 2

Activity sheet

2.7a Taking its place

Metals have different reactivities. The more reactive a metal, the quicker it will react with oxygen, water or acid. Metals will also displace less reactive metals from a compound in solution.

So try this

Put about 5 cm of copper sulphate solution into a large test tube. Put five spatulas of iron filings on a piece of paper. Copy the grid below, and fill in what these substances look like. Put the iron filings into the copper sulphate solution and give the test tube a good stir with a spatula. Stop after a few seconds, leave it to settle and observe the change. Continue stirring, but after 30 seconds and after 1 minute leave the mixture to settle again. Look at the mixture carefully, particularly the colours of the metal and the solution. Write down if there are more changes.

Make a record

Fill in your final observation in your observation grid.

Observation grid

Copper sulphate Iron filings on their The substances after solution on its own own mixing and shaking Drawing Drawing Drawing

Description

Description

Description

Explain what happened in your own words. Use this word equation to help you with your explanation. iron metal copper sulphate solution iron sulphate solution copper

63

Hodder Science Teacher's Resource C © 2003 Hodder & Stoughton Educational

Chapter 2

Activity sheet

2.7b Taking its place

Metals will displace less reactive metals from a compound in solution. Use the technique below to compare the reactivities of these metals: Copper Magnesium Lead Zinc Iron

3­ 4 drops of solution

small square of metal (0.5 cm × 0.5 cm)

flat plastic sheet such as a document pocket

One of the interesting `microscale' chemistry techniques introduced by the Royal Society of Chemistry is to carry out reactions in a `blob' of solution formed from two or three drops sitting together on a plastic surface. The plastic can be a document pocket, a laminated sheet of card or a piece of cling film. It works best if the plastic has a white background behind it. The names of the chemicals can be written on the plastic or on the white background.

So try this

Carry out the microscale technique, using pieces of metal foil about 5 mm square or ­ in the case of iron ­ a small piece of wire.

Make a record

Lay your results out in the form of a grid like the one below.

copper copper sulphate solution NO REACTION magnesium copper sulphate solution copper magnesium sulphate solution copper lead sulphate solution copper zinc sulphate solution copper iron sulphate solution

magnesium magnesium sulphate solution NO REACTION lead magnesium sulphate solution

magnesium lead sulphate solution

magnesium zinc sulphate solution

magnesium iron sulphate solution

lead copper sulphate solution

lead lead sulphate solution NO REACTION zinc lead sulphate solution

lead zinc sulphate solution

lead iron sulphate solution

zinc copper sulphate solution

zinc magnesium sulphate solution

zinc zinc sulphate solution NO REACTION iron zinc sulphate solution

zinc iron sulphate solution

iron copper sulphate solution

iron magnesium sulphate solution

iron lead sulphate solution

iron iron sulphate solution NO REACTION

Make a copy of a similar table as an answer grid. Put a tick for a piece of metal that shows a change ­ you may need a magnifying glass to see the change. Decide on an order of reactivity, with the most reactive metal at the top of your list. Write word equations for some of the reactions that resulted in a change.

64 Hodder Science Teacher's Resource C © 2003 Hodder & Stoughton Educational

Chapter 2

Homework sheet

2.7 A metal superstar

Many parts of the fastest modern planes have parts made from titanium. Titanium is also used to make replacement hip joints and low-mass bicycle frames. Compared to steel, titanium offers several advantages. Its density is only about half that of steel, so parts made from titanium weigh roughly half as much as steel parts. Despite this, the strength of titanium exceeds that of steel, and it has twice steel's elasticity. That makes titanium ideal for uses that require a flexible material that won't crack or rupture ­ such as aircraft and bicycle frames. And as a bonus, titanium resists corrosion better than the best stainless steels. There are drawbacks, however. Titanium is a poor thermal conductor. In particular, heat generated while the metal is being cut doesn't spread out through the part being cut. The heat builds up in the cutting area. You can get very high temperatures ­ 1400 C in some cases. These temperatures temper and dull the cutting edges of drills and other tools. These dull edges generate even more heat, further shortening tool life. Cutting temperatures can get so high that chips of the metal sometimes burst into flames. Another problem is that the elasticity of the titanium metal, which is so useful in the finished parts, makes it especially difficult to machine. Under cutting pressures, the `springy' materials move away from the tool. Consequently, the cutting edges rub rather than cut, particularly when making light cuts. The rubbing process generates more heat, making these problems even worse. Titanium minerals are quite common so the metal is fairly cheap. The metal burns in air and is the only element that burns in nitrogen. It is marvellous in fireworks. Titanium is resistant to dilute sulphuric and hydrochloric acid, and even to corrosive substances such as damp chlorine gas and chloride solutions such as sea water. Titanium metal is considered to be physiologically inert. It has been used for many years as the only suitable material for replacement hip joints.

Activity

1 Read the passage and underline everything about the properties of the metal in blue. 2 Underline everything about the reactions of the metal in red. 3 Underline everything about the difficulties in cutting and shaping the metal in green. 4 Underline everything about the uses of the metal in black. 5 For an English oral test you have to speak about titanium metal for TWO MINUTES (a surprisingly long time!). Write a script for a radio interview explaining about titanium. Include the questions you should be asked.

Hodder Science Teacher's Resource C © 2003 Hodder & Stoughton Educational 65

Pupil's Book C Chapter 2

2.8 Unspoilt Antarctic

Rationale

This spread continues the theme of the reactivity series for metals. It brings in the negative side of metal ore exploitation and the pollution or mess that this can cause. It begins to set the scene for ideas about sustainable development later in Pupil's Book C. In this chapter are the safe but spectacular reactions between copper oxide and zinc powder, and iron oxide and aluminium powder. These really are awe, wonder and wow reactions. They should be presented as such. Good additional resources about metals are available from Rio Tinto Zinc and other metal industry companies. Contact the Royal Society for Chemistry to get details of other resources. results with the displacement from solution results in Activities 2.7a and 2.7b. Further investigate the reactivity series by setting up simple cells using sodium chloride as the electrolyte. This gives a quantitative edge to the reactivity series measurement.

Suggested finisher

There is no need for a separate finisher activity, the practical session will take up the whole of the remaining time. There needs to be time at the end given to writing up a record of the practical and the teacher describing the pattern in the results, this will act as a plenary.

Homework

Learning outcomes

Most pupils will understand that: metal ores come from rocks on the Earth's surface metal ores do not contain a lot of metal alone when metals are extracted from rocks, this leaves a lot of mess and waste rock on the surface metals of different reactivities need different extraction methods direct competition and displacement reactions release metals from their compounds. The faster pupils will understand that: some metals can be extracted by direct competition reactions some metals can only be extracted by electrolysis. Those who learn less quickly will understand that: extracting metals is an important industry in the world like many human activities, making metals affects the environment.

Homework 2.8 Mini furnace reaction: A demonstration of the thermit reaction.

Suggested starter

Recap the learning objectives from the whole of the unit using the Targets sheet. Get the pupils to stick the completed Target sheet into their books as a record of what they have learnt. The recap of the learning targets for this activity may take up to 20 minutes of the lesson

Main activity

Then pupils should complete a test for this unit. A new short Key ideas test can be found on the CD-ROM. In addition test material can be found in the Hodder Science Assessment Pack. This includes for each unit, a SATs-style test, a very simple low-level-test for slower learners, extension questions to add to tests for faster learners, and Ideas & Evidence questions to add to tests.

Suggested finisher

Pupils should complete the end-of-unit test.

Homework

Lesson plan

2 hours/lessons

Suggested starter

Use the Finishing Off activity on page 32 of Pupil's Book C.

Starter D Equations sequencing: Use this to revise and recap work on equations. This contains cards that form the starts, middles and ends of eight `salts' equations.

Main activity

Suggestions

Literacy

Make a vocabulary list for the whole of the metals topic. Use this list to learn spellings and meanings of key words in the topic. Practise sentence construction by using each word correctly in a sentence about metals chemistry.

The climax of this spread should be the copper oxide and zinc reaction that can be found in Activity 2.8. This, combined with a demonstration of the thermit reaction (see Homework 2.8), will provide a spectacular climax to the chapter. Start with Spread 2.8. Question pupils about where different metals come from to establish their previous knowledge of this topic. Work through the idea that the extraction of metals relates to the reactivity series. A mini-debate could take place on the subject of unspoilt Antarctica. Do pupils want cheap metal goods, or do they want to preserve an unspoilt (uninhabited, relatively unvisited) wilderness? Activity 2.8 Slugger Copper vs Hard Man Zinc: Now use this practical activity to consolidate the key idea of the reactivity series. Compare the direct reaction

66

Numeracy

If the cell voltages practical has been carried out, then a quantitative summary of the reactivity series can be made. Students should find that voltage (metal x-z) voltage (metal x-y) voltage (metal y-z)

Further quantitative data could be found about the recycling of metals. A suitable question is: does recycling relate to the use of metals or their reactivity? (Hint: gold is almost 100% recycled after it is used).

ICT

Use the Internet to explore where metals are produced.

Pupil's Book C Chapter 2

Cover friendly rating

0 stars (Activity ­ hazardous and hot); 4 star (textbook); 4 star (Homework)

See appropriate CLEAPSS Hazcard and Recipe Card. A 100 cm3 bottle, with the required hazard label, should be sufficient for each group.

Cross curricular links

Geography (metal ores), D&T (thermit; uses of metals)

Advice on investigation

See the relevant CLEAPSS Hazcards for the disposal of the products of the reactions.

Technician's notes

Equipment

Beaker (100 cm Pyrex or equivalent) Bunsen burner, tripod, bench mat Copper (II) oxide* (Harmful) Hydrochloric acid 1M (Irritant) Spatula (metal) Stirring rod Tin lid Eye protection Measuring cylinder (100 cm3 glass or plastic) Matches Zinc powder* (Flammable) Safety screen Experimental notes

3

Answers

Quantity/group

1 1 1 1 1 1 1 1/student 1 1 1 1

1 Iron, copper, titanium, chromium, nickel, platinum, cobalt, gold, silver, lead, zinc, uranium 2 The newspaper article should talk about the usefulness of the materials to the world. 3 The letter should talk about the damage to the environment that the mining would cause. 4 ­ 5 The reaction mixture glows, giving out lots of heat and light. 6 iron oxide carbon monoxide iron carbon dioxide aluminium oxide aluminium + oxygen aluminium chromium oxide chromium aluminium oxide 7 Potassium, sodium, lithium, calcium, magnesium, aluminium, zinc, iron, chromium

Match to

National Curriculum references

3.1 c, e, f, 3.3 c

* See appropriate CLEAPSS Hazcard. Supply a small amount in a labelled container with the required hazard label.

67

Chapter 2

Activity sheet

2.8 Slugger Copper vs Hard Man Zinc

Copper oxide and zinc metal powder can be made to take part in a direct competition reaction. If they are mixed and heated, the copper and zinc fight for the oxygen. The more reactive metal wins.

tin lid small pile of copper oxide and zinc powder

Bunsen burner

tripod

hydrochloric acid

heat-proof mat

If the reacted mixture is placed in acid, zinc, copper oxide and zinc oxide will dissolve. Any undissolved material must be copper metal produced by the reaction.

Safety first

Wear your eye protection at every stage of this experiment.

So try this

Put a spatula of copper oxide and a spatula of zinc powder on a piece of paper. Copy the observation grid below onto an A4 page and fill in a description of the two chemicals. Mix the chemicals thoroughly using a metal spatula, and make a small conical pile on a tin lid. Put the tin lid on top of a tripod. Under this, light a Bunsen burner with a blue flame. Put a safety screen around the apparatus and stand back about 3 metres. When the reaction has finished, turn off the Bunsen and allow the mixture to cool. Fill in the observation grid. When the mixture is cool, scrape it into a 100 cm3 beaker. Add 40 cm3 of 1 M hydrochloric acid to the beaker. Stir the mixture for several minutes. If you can't see a reaction, heat the mixture gently over a Bunsen flame, but not above `steaming' temperature. Allow any reaction to subside and let the mixture settle. Copy and complete the observation grid.

Observation grid

Copper oxide Description During reaction Description Drawing Zinc powder Description After cooling Description After dissolving in acid Description

Report

Explain in writing why there is sufficient evidence to say that a reaction has taken place. Write a word (or symbol) equation for the reaction.

68 Hodder Science Teacher's Resource C © 2003 Hodder & Stoughton Educational

Chapter 2

Homework sheet

2.8 Mini furnace reaction

It takes a temperature of about 1500 °C to melt railway steel, but that is what the thermit reaction does. To repair a damaged steel rail, the rails are cut, bolted in place and a gap is left. A container of thermit mixture is placed over the gap. Thermit mixture is aluminium powder and iron oxide. The mixture is ignited with magnesium powder. The magnesium burns in air and this provides enough heat to start the reaction between the aluminium and iron oxide. The aluminium metal steals the oxygen from the iron oxide. This makes aluminium oxide, which has low density, and heavier molten iron metal. The iron flows down into the gap between the rails where it is left to solidify. The solidified aluminium oxide breaks away when hit with a hammer because it is brittle. The energy needed to cause the reaction is released because the products of the reaction contain less stored chemical energy than the starting materials. The starting materials are called the reactants. You can carry out the thermit reaction in school using the procedure given below: Make sure the reactants are dry. Mix 30 g of aluminium powder with 80 g of iron oxide. Place this mixture in a container made of aluminium foil. Place the aluminium container in a sand bucket. Wearing goggles, ignite the mixture using magnesium powder and match heads. Do the reaction outside in the open air. Stand well back.

Questions

1 2 3 4 5 6 7 8 9 10 What is thermit mixture used for? How hot does the mixture get when it is reacting? How does magnesium get the reaction started? What is in thermit mixture? Write a word equation for the reaction. Why is energy released by the chemical change, making the mixture red hot? What safety precautions are needed when carrying out this reaction? When cold, thermit mixture is considered a low hazard. Why do you think this is? Draw a cross section of the apparatus used to carry out the thermit reaction in the school grounds. Why is there a greater mass of iron oxide in thermit mixture than aluminium powder?

69

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