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Boardworks GCSE Additional Science: Chemistry Chemical Reactions

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Presentation on theme: "Boardworks GCSE Additional Science: Chemistry Chemical Reactions"— Presentation transcript:

1 Boardworks GCSE Additional Science: Chemistry Chemical Reactions

2 Boardworks GCSE Additional Science: Chemistry Chemical Reactions

3 What is a chemical reaction?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions A chemical reaction is a change that takes place when one or more substances (called reactants) form one or more new substances (called products). reactants products For example: carbon carbon dioxide oxygen +

4 Reactions all around us
Boardworks GCSE Additional Science: Chemistry Chemical Reactions How many chemical reactions go on around us everyday? Teacher notes This illustration contains several examples of everyday chemical reactions, including: cooking food: food cooks on a charcoal BBQ as a result of combustion drinking beer: beer is produced by fermentation dog panting: animals breathe for respiration face painting: some types of paint are removed by a chemical reaction with a solvent mouldy food: food becomes spoiled as a result of decay portable toilets: a chemical solution disinfects waste and changes it into a sludge dyed hair: hair colorants react with hair follicles fireworks: their explosive effects are produced by combustion rusty tractor: rust is an oxidation reaction fertilizer: ammonia, a major ingredients in many fertilizers is made by the Haber process.

5 How can you spot a chemical reaction?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Chemical reactions can appear very different. As you observe a chemical reaction, you may detect: a colour change precipitate (solid) forming energy being produced (fizzing, burning) an odour being produced. Teacher notes The four reactions shown in the cartoons are: Neutralization (top right) The neutralization reaction between hydrochloric acid and calcium carbonate to produce carbon dioxide, calcium chloride and water. Precipitation (bottom right) Various precipitation reactions, including, on the far right, the reaction between iron (III) chloride (yellow solution) and sodium hydroxide to produce iron (III) hydroxide (deep brown solid) and sodium chloride. Oxidation (bottom middle) Magnesium ribbon burning, and about to be added to a gas jar of oxygen. Reversible (bottom left) Heating hydrated copper (II) sulfate (blue) to produce anhydrous copper (II) sulfate (white) and water.

6 Why doesn’t the mass change?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions In a chemical reaction, no atoms are made or destroyed. The reaction just changes how the atoms are bonded together.

7 Does mass change during a reaction?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This three-stage interactive animation shows how mass remains constant during a reaction.

8 Boardworks GCSE Additional Science: Chemistry Chemical Reactions
What is a word equation? Boardworks GCSE Additional Science: Chemistry Chemical Reactions A word equation uses the names of the reactants and products to show what happens in a chemical reaction. For example, when a piece of sulfur is burned in oxygen gas it produces a white solid called sulfur dioxide. The word equation for this reaction is: Photo credit: Charles D. Winters / Science Photo Library Image shows a blue-green light being emitted by a sample of sulfur powder burning in a conical flask of oxygen. + sulfur oxygen dioxide

9 What is a symbol equation?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions A symbol equation uses the formulae of the reactants and products to show what happens in a chemical reaction. A symbol equation must be balanced to give the correct ratio of reactants and products. + S O2 SO2 This equation shows that one atom of sulfur (S) reacts with one molecule of oxygen (O2) to make one molecule of sulfur dioxide (SO2). +

10 What do state symbols show?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions State symbols are added to a symbol equation to show whether the reactants and products are: solid – symbol is (s) liquid – symbol is (l) gas – symbol is (g) dissolved in water – symbol is (aq). + S (s) O2 (g) SO2 (g) With state symbols in place, this symbol equation now shows that the sulfur is a solid, the oxygen is a gas and the sulfur dioxide is also a gas.

11 Chemical reactions – true or false?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This true-or-false quiz could be used as a starter exercise to work on chemical reactions. Students could be given coloured traffic light cards (red = false, green = true) to vote on the statements shown. To stretch students, they could be asked to explain their voting.

12 Boardworks GCSE Additional Science: Chemistry Chemical Reactions

13 What is thermal decomposition?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions

14 Thermal decomposition – easy or hard?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions The more reactive a metal, the harder it is to decompose its carbonate by heating. potassium sodium calcium magnesium aluminium manganese zinc iron copper silver gold increase in reactivity Predict how easy it is to decompose these carbonates: copper carbonate calcium carbonate sodium carbonate manganese carbonate zinc carbonate iron carbonate.

15 Thermal decomposition – activity
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This ordering activity could be used as a plenary or revision exercise on thermal decomposition. Mini-whiteboards could be used to make this a whole-class exercise.

16 Thermal decomposition of carbonates
Boardworks GCSE Additional Science: Chemistry Chemical Reactions When the metal carbonate is heated, it decomposes to produce a metal oxide and carbon dioxide. FeO FeCO3 + CO2 iron oxide iron carbonate carbon dioxide heat What are the word and symbol equations for the thermal decomposition of these carbonates? copper carbonate manganese carbonate zinc carbonate.

17 Heating calcium carbonate
Boardworks GCSE Additional Science: Chemistry Chemical Reactions When calcium carbonate is heated, it decomposes to produce calcium oxide and carbon dioxide. This reaction is carried out in industry to make calcium oxide (quicklime) from calcium carbonate (limestone): CaO CaCO3 + CO2 calcium oxide calcium carbonate carbon dioxide heat Photo credit: Daniel Jaeger Vendruscolo Calcium oxide is used to make concrete and calcium hydroxide (slaked lime).

18 Heating sodium hydrogencarbonate
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Baking powder and self-raising flour contain sodium hydrogencarbonate (also known as sodium bicarbonate). When sodium hydrogencarbonate is heated, it decomposes to make sodium oxide, carbon dioxide and water. What effect does this reaction have on dough as it is being baked? Photo credit: © 2007 Jupiterimages Corporation The carbon dioxide released during the reaction creates tiny bubbles, which help the dough to rise.

19 What is the decomposition equation?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This drag and drop activity could be used as a plenary exercise to check students’ ability to write word equations for reactions. Mini-whiteboards could be used to make this a whole-class exercise.

20 Boardworks GCSE Additional Science: Chemistry Chemical Reactions

21 Boardworks GCSE Additional Science: Chemistry Chemical Reactions
What are indicators? Boardworks GCSE Additional Science: Chemistry Chemical Reactions Indicators are chemicals that change colour in the presence of an acid or an alkali. There are many different indicators. Lots of them come from plants, like red cabbage. Different indicators turn different colours. Geranium plants grown in acidic soil have red flowers, while geraniums grown in alkali soil have blue flowers. Universal indicator is a mixture of indicators. It is useful because it shows a range of colours from pH 1–14.

22 What does the pH scale show?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions The pH scale runs from 1 to 14. The numbers 1 to 6 represent acidic conditions and 8 to 14 represent alkali conditions. A pH value 7 is neutral. What are the pH values of some everyday items? 1 2 3 4 5 6 7 8 9 10 11 12 13 14

23 Boardworks GCSE Additional Science: Chemistry Chemical Reactions
What is the order of pH? Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This ordering activity could be used as a plenary or revision exercise on pH. Mini-whiteboards could be used to make this a whole-class exercise.

24 Boardworks GCSE Additional Science: Chemistry Chemical Reactions
What are acids? Boardworks GCSE Additional Science: Chemistry Chemical Reactions Acids are substances that: Have a pH below 7 and turn universal indicator yellow, orange or red. Turn litmus red. Form solutions containing hydrogen ions (H+). Photo credit: © 2007 Jupiterimages Corporation Teacher notes The more hydrogen ions in the solution, the stronger the acid. Hydrochloric acid is a strong acid. Ethanoic acid (vinegar) is a weak acid.

25 Boardworks GCSE Additional Science: Chemistry Chemical Reactions
What are alkalis? Boardworks GCSE Additional Science: Chemistry Chemical Reactions Alkalis are substances that: Have a pH above 7 and turn universal indicator blue or purple. Turn litmus blue. Can neutralize acids Form solutions containing hydrogen ions (H+). Sodium hydroxide is a strong alkali. Photo credit: © 2007 Jupiterimages Corporation Ammonia is a weak alkali. When ammonia is dissolved in water, it forms ammonium hydroxide (NH4OH), a fertilizer.

26 Boardworks GCSE Additional Science: Chemistry Chemical Reactions
What are bases? Boardworks GCSE Additional Science: Chemistry Chemical Reactions All alkalis are bases. Bases are substances that react with acids by absorbing hydrogen ions (H+). The oxides, hydroxides and carbonates of metals, such as sodium hydroxide, are bases. Ammonia is a base that does not contain a metal. alkalis (soluble bases) bases (react with acids) Some bases are soluble in water – these are called alkalis. All alkalis contain hydroxide ions (OH–). The more OH– ions in the solution, the stronger the alkali.

27 Acids and bases – true or false?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This true-or-false quiz could be used as a starter exercise to work on acids and bases. Students could be given coloured traffic light cards (red = false, green = true) to vote on the statements shown. To stretch students, they could be asked to explain their voting.

28 Boardworks GCSE Additional Science: Chemistry Chemical Reactions

29 How are salts made and named?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions When an acid reacts with a base, a neutralization reaction occurs and produces a chemical called a salt. + acid base a salt The name of the salt depends on the names of the reactants. The first part of the salt’s name comes from the base: e.g. sodium hydroxide sodium… The second part of the salt’s name comes from the acid: e.g. sulfuric acid sulfate… For example, if sodium hydroxide neutralizes sulfuric acid, the product is a salt called sodium sulfate.

30 What is the name of the salt?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This drag and drop activity provides the opportunity for informal assessment of students’ understanding of how salts are named.

31 Boardworks GCSE Additional Science: Chemistry Chemical Reactions
What are salts used for? Boardworks GCSE Additional Science: Chemistry Chemical Reactions The colours of fireworks are formed when certain salts burn. Calcium chloride, for example, burns a bright red colour. Table salt is sodium chloride. This is the salt used to flavour and preserve food. Indigestion remedies often contain magnesium salts. Photo credit: © 2007 Jupiterimages Corporation Teacher notes Salt is also put on icy roads to melt the ice, and used to make many other useful chemicals. Some salts are used as fertilisers. Ammonium salts are especially good for this because they are sources of nitrogen. Iron sulfate is used as a weed killer on lawns. Calcium sulfate is used in plaster of Paris. Salts can also be used as coloured pigments in paints, and to help fuels burn better.

32 Making salts 1: acid + alkali
Boardworks GCSE Additional Science: Chemistry Chemical Reactions When an acid reacts with an alkali, the products are a salt and water. acid alkali salt water + Water is formed because OH– ions from the alkali react with H+ ions from the acid to produce molecules of water (H2O). For example: + sodium hydroxide NaOH (aq) sodium chloride NaCl (aq) water H2O (aq) hydrochloric acid HCl (aq)

33 When is the reaction complete?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions The reaction between sodium hydroxide and hydrochloric acid produces sodium chloride, which is soluble in water. + sodium hydroxide NaOH (aq) sodium chloride NaCl (aq) water H2O (aq) hydrochloric acid HCl (aq) There is no obvious sign when this reaction is complete, so an indicator is used to show when the solution is neutral. This process is called titration.

34 Boardworks GCSE Additional Science: Chemistry Chemical Reactions
What is a titration? Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This four-stage animation shows how titration is used to find the concentration of a solute in a solution.

35 Making salts 2: acid + metal
Boardworks GCSE Additional Science: Chemistry Chemical Reactions When a metal is added to an acid, the products are a salt and hydrogen gas. acid metal a salt hydrogen + For example: hydrochloric acid 2HCl (aq) + zinc Zn (aq) zinc chloride ZnCl2 (aq) hydrogen H2 (aq) This method of making salts only works with some metals. What would happen if potassium was used? Or copper?

36 Which metal will react the most?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This six-stage animation shows how salts are obtained from the reactions between acids and metals.

37 Making salts 3: acid + metal oxide
Boardworks GCSE Additional Science: Chemistry Chemical Reactions When a metal oxide is mixed with an acid, the products are a salt and water. acid metal oxide salt water + Water forms because oxygen ions from the oxide join up with H+ ions from the acid to produce molecules of water (H2O). For example: calcium chloride + water calcium oxide CaO (aq) hydrochloric acid 2HCl (aq) CaCl2 (aq) H2O (aq)

38 Obtaining salts from metal oxides
Boardworks GCSE Additional Science: Chemistry Chemical Reactions When a metal oxide is added to an acid, it dissolves as it reacts. You know when you have added enough of the metal oxide because it stops dissolving. + copper oxide CuO (s) sulfuric acid H2SO4 (aq) sulfate CuSO4 (aq) water H2O (aq) How could the solid copper sulfate salt be separated from the water?

39 Obtaining salts from copper oxide
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This four-stage animation shows how a salt is obtained from copper oxide powder.

40 Making salts 4: acid + carbonate
Boardworks GCSE Additional Science: Chemistry Chemical Reactions When a carbonate is mixed with an acid, the products are a salt, carbon dioxide and water. acid carbonate salt water + carbon dioxide Water and carbon dioxide are formed because the carbonate ions (CO32-) react with H+ ions from the acid. For example: copper nitrate + water carbon dioxide copper carbonate CuCO3 (s) nitric acid 2HNO3 (aq) Cu(NO3)2 (aq) H2O (aq) CO2 (g) What would you expect observe in this reaction?

41 Boardworks GCSE Additional Science: Chemistry Chemical Reactions
Making salts – summary Boardworks GCSE Additional Science: Chemistry Chemical Reactions Salts can be made by reacting acids with bases. There are four ways of making salts from acids: acid + metal a salt + hydrogen acid + base a salt + water acid + carbonate a salt + carbon dioxide + water

42 Matching reactants and salts
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This matching activity could be used as a plenary or revision exercise on salts. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.

43 Complete the neutralization reaction
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This drag and drop activity could be used as a plenary exercise to check students’ ability to write word equations for reactions. Mini-whiteboards could be used to make this a whole-class exercise.

44 Boardworks GCSE Additional Science: Chemistry Chemical Reactions

45 What is a precipitation reaction?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Sometimes when two solutions are mixed, they react to form an insoluble solid product. The insoluble solid product is called a precipitate. You can spot a precipitate because the mixture goes cloudy. For example, mixing solutions of lead nitrate and sodium chloride produces a yellow precipitate of lead chloride. lead nitrate Pb(NO3)2 (aq) sodium chloride 2NaCl (aq) PbCl2 (s) 2NaNO3 (aq) +

46 How can hard water be softened?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Hard water contains magnesium and calcium ions, which can clog up pipes and heating elements. These ions can be removed using precipitation reactions. Sodium carbonate is added to the hard water to form precipitates, which can then be removed by filtration. The magnesium ions are removed by this reaction: sodium carbonate Na2CO3 (aq) magnesium chloride MgCl2 (aq) 2NaCl (aq) MgCO3 (s) + What are the word and symbol equations for the removal of the calcium ions?

47 Precipitates of hydoxides
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Many metals form hydroxide precipitates, which have characteristic colours. For example, when sodium hydroxide solution is added to a solution of iron(III) chloride, the reaction produces a brown precipitate of iron(III) hydroxide. + FeCl3 (aq) 3NaOH (aq) Fe(OH)3 (s) 3NaCl (aq) iron(III) chloride sodium hydroxide

48 Identifying precipitates
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This drag and drop activity could be used as a plenary exercise to check students’ ability to interpret chemical formulae. Mini-whiteboards could be used to make this a whole-class exercise.

49 Boardworks GCSE Additional Science: Chemistry Chemical Reactions
Identifying metals Boardworks GCSE Additional Science: Chemistry Chemical Reactions

50 Precipitation – true or false?
Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This true-or-false quiz could be used as a starter exercise to work on precipitation reactions. Students could be given coloured traffic light cards (red = false, green = true) to vote on the statements shown. To stretch students, they could be asked to explain their voting.

51 Boardworks GCSE Additional Science: Chemistry Chemical Reactions

52 Boardworks GCSE Additional Science: Chemistry Chemical Reactions
Glossary Boardworks GCSE Additional Science: Chemistry Chemical Reactions acid – A substance that releases H+ ions in solution. alkali – A substance that releases OH- ions in solution. base – Any substance that reacts with an acid. decomposition – A type of reaction in which a compound is broken down into two or more substances. neutralization – A type of reaction in which an acid reacts with a base to produce a salt. precipitate – A solid, insoluble product of a reaction. precipitation – A type of reaction in which two aqueous solutions react to form an insoluble product. salt – A substance formed when an acid reacts with a base. titration – A method of indicating when an undetectable reaction, such as neutralization, is complete.

53 Boardworks GCSE Additional Science: Chemistry Chemical Reactions
Anagrams Boardworks GCSE Additional Science: Chemistry Chemical Reactions

54 Boardworks GCSE Additional Science: Chemistry Chemical Reactions
Completing equations Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This drag and drop activity could be used as a plenary exercise to check students’ ability to write word equations for reactions. Mini-whiteboards could be used to make this a whole-class exercise.

55 Boardworks GCSE Additional Science: Chemistry Chemical Reactions
Multiple-choice quiz Boardworks GCSE Additional Science: Chemistry Chemical Reactions Teacher notes This multiple-choice quiz could be used as a plenary activity to assess students’ understanding of chemical reactions. The questions can be skipped through without answering by clicking “next”. Students could be asked to complete the questions in their books and the activity could be concluded by the completion on the IWB.


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