Reacting Metals with Acids E2 Core

Activity

Reacting metals with acids E2 Core

Aim To find out how metals react with acids. Equipment six test tubes and rack wooden splints dilute hydrochloric acid Bunsen burner dilute sulphuric acid heatproof mat pieces of magnesium, zinc and copper foil

burning splint

dilute acid metal

Wear eye protection. Take care not to get acid on

your skin or clothes. What to do 1 Draw a table like the one on the next sheet ready to record your results. 2 Pour about 2 cm depth of dilute hydrochloric acid into a test tube in a rack. 3 Add a small piece of magnesium to the acid in the test tube. Immediately put your finger or thumb over the end of the test tube. 4 After about one minute, bring a lighted splint to the end of the test tube as you take your finger or thumb away. 5 Feel the bottom of the tube to see if it is hot. 6 Record the results in your table. 7 Repeat steps2 to6 using sulphuric acid instead of hydrochloric acid. 8 Repeat steps2 to7 using zinc instead of magnesium. You may not be able to collect enough gas to test with a lighted splint this time. 9 Repeat steps2 to7 using copper instead of magnesium. Do not carry out the test with a lighted splint this time. Continued

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Reacting metals with acids E2 continued Core

Results

Metal Acid Observations Results of test with lighted splint

Questions 1 Which metals reacted with the two acids? 2 Was the same gas produced in each reaction? 3 Write a word equation for the reaction between magnesium and hydrochloric acid. 4 Copper did not react with the acids. How do you know that a reaction did not take place?

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C D Lees, 2002, The Heinemann Science Scheme Activity

Reacting carbonates with acids E3 Core

Aim To find out how metal carbonates react with acids. Equipment dilute hydrochloric acid delivery tube and bung sodium carbonate limewater copper carbonate spatula four test tubes and rack clamp stand

delivery tube

Wear eye protection. Take care not to get acid on your skin or clothes.

dilute acid limewater metal carbonate

What to do 1 Draw a table like the one below ready to record your results. 2 Pour about 2 cm depth of dilute hydrochloric acid into a test tube. 3 Pour some limewater into another test tube so that it is about half full. 4 Get a delivery tube ready with the delivery end in the limewater. 5 Add a spatula measure of sodium carbonate to the test tube containing hydrochloric acid. Immediately fit the delivery tube to this test tube to bubble gas through the limewater. 6 Feel the bottom of the tube containing acid and carbonate to see if it is hot. 7 Record your observations in your table. 8 Repeat steps2 to7 using a few small pieces of copper carbonate instead of sodium carbonate. Results Metal carbonate Observations in acid test Observations in limewater tube test tube

Continued

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Reacting carbonates with acids E3 continued Core

Questions 1 What observations showed you that a reaction takes place between sodium carbonate and hydrochloric acid? 2 Which gas was produced in both of the reactions you carried out? 3 What additional substance is produced, other than a salt and carbon dioxide, in these reactions? 4 What observation showed you that a salt was produced when copper carbonate reacted with hydrochloric acid? 5 Write a word equation for the reaction of copper carbonate with hydrochloric acid.

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C D Lees, 2002, The Heinemann Science Scheme Activity

Reacting metal oxides with acids E4 Core

Aim To find what happens when metal oxides react with acids. Equipment beaker dilute sulphuric acid filter funnel Bunsen burner boiling tube filter paper tripod and gauze copper oxide evaporating basin heatproof mat spatula What to do 1 Draw a table like the one on the next page ready to record your results. Record your observations at each stage.

2 Set up a beaker half filled with water on a tripod and gauze. Wear eye protection. Take care not to get acid on Heat the water to boiling using a Bunsen burner. Turn off the your skin or clothes. Bunsen burner when the water is boiling. 3 Pour about 3 cm depth of dilute sulphuric acid into a boiling tube. 4 Add two spatula measures of copper oxide to the sulphuric acid. 5 Place the boiling tube in the beaker of hot water for a few minutes. Every minute remove the boiling tube to shake the contents of the tube. If all of the copper oxide disappears, hot water sulphuric acid and add another spatula measure. copper oxide

y yy yy

yy yy

yy y

yy y yy yy

y 6 When no more copper oxide will disappear, filter the contents of the tube, collecting the filtrate in an evaporating basin.

7 Place the evaporating basin on the tripod filtrate

y yy

yy yy

y y

yy yy

yy y y yy

evaporating y

y y

y and gauze. Boil the filtrate until only y basin about a third of the original volume is left. 8 Leave your evaporating basin and remaining liquid to cool. Then look at them and record the appearance of the final product.

Continued

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Reacting metal oxides with acids E4 continued Core

Results Appearance of Appearance of Appearance of Appearance of acid and oxide acid and oxide filtrate final product before heating after heating

Questions 1 Why were the copper oxide and sulphuric acid heated? 2 Why were the contents of the test tube filtered? 3 What was formed at the end of the experiment? 4 Write a word equation for the reaction between copper oxide and sulphuric acid. 5 Why were no bubbles seen as the copper oxide and sulphuric acid reacted?

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C D Lees, 2002, The Heinemann Science Scheme Activity

Neutralising an acid with an E5a alkali Core

Aim To find out what happens when an alkali is added to an acid. Equipment For the demonstration: Wear eye protection. dilute potassium 25 cm3 pipette pH probe hydroxide solution safety pipette filler temperature sensor dilute hydrochloric 50 cm3 burette and stand data logger acid 400 cm3 beaker computer distilled water stirrer stopwatch What to do Your teacher will demonstrate this experiment. potassium 1 Draw a table like the one hydroxide below ready to record your results. solution 2 Your teacher will set up the apparatus shown in the diagram. temperature sensor 3 3 A pipette is used to measure 25 cm of pH probe acid into the beaker. About 25 cm3 of distilled water are added. 3 4 2cm of alkali are added from to data logger the burette every minute while and the mixture is stirred. computer stirrer 5 The pH of the mixture is hydrochloric monitored using a data logger. acid 6 A temperature sensor is used to follow the temperature change in the mixture. 7 Use your results to plot a graph of pH (on the vertical axis) against volume of alkali added. Your teacher may give you a graph printed from the computer. Results Volume of alkali added (cm3) pH of mixture Temperature of mixture (8C)

Questions 1 Why was distilled water added to the acid in the beaker? 2 Describe what happened to the pH of the mixture during the experiment. 3 What volume of alkali exactly neutralises 25 cm3 of acid? Use your graph to find the answer. 4 Does the neutralisation reaction give out heat or take in heat? 5 What is the name of the salt produced in this reaction?

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C D Lees, 2002, The Heinemann Science Scheme Activity

The reactivity series of metals F3a Core

Aim To use reactions with acids to place metals in order of reactivity. Equipment samples of calcium, iron, test tube tripod and gauze copper and zinc beaker heatproof mat dilute hydrochloric acid Bunsen burner tongs What to do 1 Draw a table like the one on the next sheet ready to record your results. Wear eye protection. water Take care not to get acid on 2 Set up the apparatus as shown in the your skin or clothes.

y yy y

yy yy

y y

yy yy

y y y yy diagram. y

y y

y y y 3 Heat the water until it is about to boil, then move the Bunsen burner to one side. 4 Pour about 2 cm depth of hydrochloric acid into a test tube. 5 Put a piece of iron in the acid. 6 Note how quickly bubbles of hydrogen are produced. Score this on a scale of 1 to 10. 7 Place the tube of acid and metal into the beaker of hot water and note the time. 8 After 5 minutes of heating, note how quickly bubbles of hydrogen are hot water hydrochloric acid produced. Score this on a scale and iron

of 1 to 10. y yy yy

yy yy

y yy

yy y

yy y yy y

y 9 Repeat steps4 to8 with zinc and y copper.

10 Repeat steps4 to6 with calcium. Do not use hot water with calcium.

Do not touch the calcium. Use tongs.

Continued

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The reactivity series of metals F3a continued Core

Results Metal Rate of hydrogen Rate of hydrogen production in cold acid production in hot acid

Questions 1 Which metal produced hydrogen most rapidly in cold and hot acid? 2 Which metal did not react in cold or hot acid? 3 List the metals in order of reactivity, from most reactive to least reactive. 4 Look at your list of metals from Activity F2. Do your results agree with this list? 5 Add calcium and zinc to your reactivity series of metals. 6 How well does the data from Activities F1, F2 and F3a support the reactivity series you have written? 7 How could you get more data to support your ideas? 8 Write a word equation for the reaction of zinc with hydrochloric acid.

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C D Lees, 2002, The Heinemann Science Scheme Activity

Displacement reactions of metals F4a Core

Aim To show that a more reactive metal will displace a less reactive metal from one of its salts in solution. Equipment spotting tile samples of metal salt solutions samples of solid metals: magnesium, containing magnesium, zinc, iron, zinc, iron, copper, lead copper, lead and silver, with droppers tongs large beaker

magnesium and iron salt solution magnesium and copper salt solution magnesium and magnesium and zinc salt solution Wear eye protection. lead salt solution Wash your hands after handling chemicals. magnesium and silver salt solution

spotting tile

What to do 1 Draw a table like the one on the next sheet ready to record your results. Your teacher may give you a results table. 2 Place five pieces of one of the metals on a spotting tile, each in a separate well. Use tongs for the lead pieces, because lead is very poisonous. 3 Cover the pieces of metal on your spotting tile with a few drops of metal salt solution. Use a different solution for each piece of metal. Do not use a solution containing the same metal as the pieces on the tile – for example, for lead, do not use a lead salt solution. Make sure the pieces of metal are fully covered by the solutions. 4 Watch for a few minutes to see what happens. If the solid metal displaces metal ions from the solution, it will change colour (usually the metal turns black) or fizz. 5 Record the results in your table. 6 Empty the metal pieces into the beaker provided, and wash your spotting tile. 7 Repeat steps2 to6 with each of the other four metals and the metal salt solutions.

Continued

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Displacement reactions of metals F4a continued Core

Results Solid metal Metal ions in Observation Did the solid metal solution displace the metal ions in solution?

Questions 1 Use your results to list the metals in order. Put the metal that displaced all of the others at the top of the list. Continue down the list with fewer displacements, until the last metal displaced none of the others. 2 Compare this list with the reactivity series of metals. Are they the same? 3 Write a sentence to describe the connection between the reactivity of a metal and its displacement of other metals from solutions of their salts. 4 Explain what happens to the more reactive metal that does the displacement and the less reactive metal that is displaced. 5 The results from Activities F1, F2 and F3a do not allow an accurate comparison of the reactivity of copper and silver. How do the results from this activity enable you to place copper and silver in the correct order in the reactivity series? 6 Write a word equation for one of the displacement reactions.

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C D Lees, 2002, The Heinemann Science Scheme Activity

Smelting copper from malachite F5b Extension

Aim To show how copper can be extracted from an ore. Equipment piece of paper carbon granules heatproof mat spatula Bunsen burner beaker crushed malachite tripod trough carbon powder pipeclay triangle tongs

tin lid Wear eye protection. Wash your hands after What to do handling chemicals. 1 On a piece of paper place one spatula measure of crushed malachite and two spatula measures of carbon powder. Mix these thoroughly. 2 Pour the mixture onto a tin lid and mixture of malachite and carbon powder covered tin lid cover it with carbon granules. with carbon granules

Arrange the apparatus as shown.

3 Heat the mixture strongly for about 5 minutes. Then turn off the pipeclay triangle Bunsen burner and leave the mixture to cool for about 5 minutes. 4 Half fill the beaker with water. Pour the mixture into the water. 5 Swirl the mixture and water in the beaker, pouring out some of the water and the lighter powder into a trough every few seconds. 6 Look for tiny pieces of copper in the heavier powder that sinks to the bottom. Results 7 Note down your observations at each stage of the activity. Questions 1 Malachite is an ore of copper containing copper carbonate. When this is heated, carbon dioxide is given off and copper oxide is formed. Copy and complete this word equation and write a symbol equation for this reaction. copper copper ϩ 2 Hot carbon removes the oxygen from the copper oxide, forming copper metal. The copper oxide is reduced. Carbon is oxidised as the oxygen joins onto it to form carbon dioxide. Write word and symbol equations for this reaction. 3 Hot copper reacts with oxygen in the air to form copper oxide. Use this idea to explain why the mixture was covered with carbon granules before it was heated. 4 Copper used for electrical wiring must be very pure. What would need to be done to the copper from this smelting reaction before it could be used for this?

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The change in mass when magnesium burns

Class practical Magnesium is weighed and then heated in a crucible. It reacts with oxygen to produce the oxide. It can be shown that there has been an increase in mass. The results can be used to find the formula of magnesium oxide and two methods are described for doing so.

Lesson organisation The practical activity takes around 30-45 minutes, depending on the competence of the class. Students should all be standing and should wear eye protection. Students with long hair should tie it back.

It is a good idea for students to practice lifting the lid on and off the crucible and the crucible off the pipe clay triangle before they start. This has the added bonus of checking that all the tongs are functioning correctly.

To enable students to light their Bunsen burners they will need access to matches or lighters. Alternatively, light one or two Bunsen’s around the room and students can light their own using a splint.

The most significant hazard in this experiment is the hot apparatus. Warn students that it will take some time to cool down.

For classes with shorter attention spans, the final step of heating to constant mass could be omitted.

Apparatus Chemicals Eye protection Magnesium ribbon, about 10-15 cm Per pair or Refer to Health & Safety and Technical notes group of section below for additional information. students: Crucible with lid Tongs Pipe clay triangle Bunsen burner Tripod Heat resistant mat Emery paper (optional) Access to: Balance (2 d.p.)

Health &Safety and Technical notes Read our standard health &safety guidance

Wear eye protection.

Magnesium ribbon, Mg(s) - see CLEAPSS Hazcard. Fresh, clean magnesium is best for this experiment. If the magnesium is tarnished then emery or sand paper will be required to clean it.

Procedure a Cut a piece of magnesium about 10-15 cm long. If it is looking tarnished or black then clean it using the emery paper. Twist it into a loose coil. b Weigh the crucible with the lid (mass 1) and then the magnesium inside the crucible with the lid (mass 2). c Set up the Bunsen burner on the heat resistant mat with the tripod. Place the pipe clay triangle over the tripod in a ‘star of David’ formation, ensuring that it is secure. Place the crucible containing the magnesium in the pipe clay triangle and put the lid on.

d Light the Bunsen burner and begin to heat the crucible. It is best to start with a gentle blue flame, but you will need to use a roaring flame (with the air hole fully open) to get the reaction to go. e Once the crucible is hot, gently lift the lid with the tongs a little to allow some oxygen to get in. You may see the magnesium begin to flare up. If the lid is off for too long then the magnesium oxide product will begin to escape. Don't let this happen. f Keep heating and lifting the lid until you see no further reaction. At this point, remove the lid and heat for another couple of minutes. Replace the lid if it appears that you are losing some product. g Turn off the Bunsen burner and allow the apparatus to cool. h Re-weigh the crucible with lid containing the product (mass 3). i Heat the crucible again for a couple of minutes and once again allow to cool. Repeat this step until the mass readings are consistent. This is called ‘heating to constant mass.’

Teaching notes Students should have recorded the following masses:

● (mass 1) Crucible + lid ● (mass 2) Crucible + lid + magnesium ● (mass 3) Crucible + lid + product This should allow them to calculate the mass of the mass of the magnesium (mass 2) - (mass 1) and the mass of the product (mass 3) - (mass 1). They could also calculate the increase in mass (mass 3) - (mass 2), which corresponds to the mass of oxygen.

The equation is: Flame colours – a demonstration 80 This demonstration experiment can be used to show the flame colours given by alkali metal, alkaline earth metal, and other metal salts. This is a spectacular version of the ‘flame tests’ experiment that can be used with chemists and non-chemists alike. It can be extended as an introduction to atomic spectra for post-16 students.

Lesson organisation This experiment must be done as a demonstration. It takes about ten minutes if all is prepared in advance. Preparation includes making up the spray bottles and conducting a risk assessment. Your employer's risk assessment must be customised by determining where to spray the flame to guarantee the audience’s safety. Use a fume cupboard unless you are sure of an alternative space.

Apparatus and chemicals Eye protection Access to fume cupboard (unless a safe alternative space is available) • Trigger pump operated spray bottles (see note 1) Bunsen burner Heat resistant mat(s) Hand-held spectroscopes or diffraction gratings (optional) Samples of the following metal salts (no more than 1 g of each) (see note 2): Sodium chloride (Low hazard) Potassium chloride (Low hazard) (see note 3) Lithium chloride (Harmful) (see note 3) Copper sulfate (Harmful, Danger to the environment). Ethanol (Highly flammable), approx 10 cm3 for each metal salt. or IDA (industrial denatured alcohol) (Highly flammable, Harmful)

243 Technical notes Sodium chloride is Low hazard. Refer to CLEAPSS® Hazcard 47B. Potassium chloride is Low hazard. Refer to CLEAPSS® Hazcard 47B. Lithium chloride is Harmful. Refer to CLEAPSS® Hazcard 47B Copper sulfate is Harmful, Danger to the environment. Refer to CLEAPSS® Hazcard 27C. Ethanol is Highly flammable. IDA (industrial denatured alcohol) is Highly flammable, Harmful. Refer to CLEAPSS® Hazcard 40A. 1 Spray bottles of the type used for products such as window cleaner should be used. These piston-operated spray bottles should be emptied, cleaned thoroughly and finally rinsed with distilled water. Ideally, one bottle is needed for each metal salt. Never use spray bottles with a rubber bulb - the flame may flash back into the container. 2 The chlorides of metals are the best but other salts also work. Make a saturated solution of each salt in about 10 cm3 ethanol. To do this, add the salt to the ethanol in small quantities, with stirring, until no more will dissolve – often only a few mg of salt will be needed. Place each solution in a spray bottle and label the bottle. The solutions can be retained for future use. They can be stored in the plastic bottles for several weeks at least without apparent deterioration of the bottles. 3 Potassium iodide and lithium iodide can be used instead. As a general rule, chlorides are usually suggested as they tend to be more volatile and more readily available. These two are in fact a little more volatile than the chloride, and potassium iodide is certainly likely to be available (refer to CLEAPSS® Hazcard 47B). Other metal salts (e.g. those of calcium and barium) can also be used provided an appropriate risk assessment is carried out. Barium chloride is toxic but gives a different colour (refer to CLEAPSS® Hazcard 10A), while calcium chloride (Irritant) and strontium chloride (Irritant) are different again (refer to CLEAPSS® Hazcard 19A). 4 Care should be taken not to allow excess ethanolic solution to accumulate on the heat resistant mats. There is a risk of this igniting with the proximity of the Bunsen burner flame.

Procedure HEALTH & SAFETY: Carry out the whole experiment in a fume cupboard or an area you have previously shown to be safe. Wear eye protection. Ensure that the spray can be safely directed away from yourself and the audience. a Darken the room if possible. b Light the Bunsen and adjust it to give a non-luminous, roaring flame (air hole open). c Conduct a preliminary spray in a safe direction away from the Bunsen flame. Adjust the nozzles of the spray bottles to give a fine mist. d Choose one spray bottle. Spray the solution into the flame in the direction you have rehearsed. Repeat with the other bottles. e A spectacular coloured flame or jet should be seen in each case. The colour of the flame depends on the metal in the salt used. f As an extension, students can view the flames through hand-held spectroscopes or diffraction gratings in order to see the line spectrum of the element. (Diffraction gratings work better. A better way to produce a steady source of light is to use discharge tubes from the Physics Department – with a suitable risk assessment.)

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