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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 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.

3 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.

4 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.

5 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)

6 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.

7 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.

8 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?

9 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.

10 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)

11 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?

12 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.

13 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 to observe in this reaction?

14 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 + alkali a salt + water acid + metal a salt + hydrogen acid + metal oxide a salt + water acid + carbonate a salt + carbon dioxide + water

15 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.

16 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.

17 Boardworks GCSE Additional Science: Chemistry Chemical Reactions

18 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) +

19 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?

20 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

21 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.

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

23 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.

24 Boardworks GCSE Additional Science: Chemistry Chemical Reactions

25 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.

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

27 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.

28 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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