Reactions of acids

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  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids Teacher notes This illustration contains several discussion points relating to acids and alkalis, including: Foods (lemons, oranges etc.): examples of some foods that are acidic or alkali Flowers (hydrangeas): hydrangeas grow blue flowers in an acidic soil, but pink flowers in an alkaline soil Acid rain: power stations and factories produce polluting gases such as sulphur dioxide, which react with water in clouds to form acid rain. Putting lime on soil: Lime raises soil pH, and is used to neutralize the acidic effects of acid rain and certain fertilizers. Brushing teeth: Depending on the brand and formulation, toothpaste is usually neutral or slightly alkaline. Toothpastes that contain fluorine tend to have a lower pH than toothpastes that contain baking soda however. Washing the tractor/cleaning products : Most cleaning products tend to be alkaline Stung by a bee: Bee stings are acidic. Wasp stings are alkaline.
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids Photo credit (left and right): © 2008 Jupiterimages Corporation
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids Photo credit: © 2008 Jupiterimages Corporation
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids Photo credit: © 2008 Jupiterimages Corporation
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids Reactions of Acids Worksheet 1 accompanies this slide. Teacher notes The gas produced during the react between an acid and a metal is hydrogen.
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids Photo credit: © 2008 Jupiterimages Corporation
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids Photo credit: Vince Petaccio
  • Boardworks KS3 Science 2008 Reactions of Acids Photo credit: Eva Jurenikova
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids Glossary acid – A chemical that has a pH less than 7. acid rain – Rain that has a pH lower than about 5.6. alkali – A chemical that has a pH greater than 7 and that dissolves in water. antacid – A medicine used to cure indigestion by neutralizing excess stomach acid. base – A substance that reacts with an acid. neutralization – The chemical reaction between an acid and an alkali. salt – A substance formed by the reaction of an acid with a base.
  • Boardworks KS3 Science 2008 Reactions of Acids
  • Boardworks KS3 Science 2008 Reactions of Acids

Transcript

  • 1. 1 of 47 © Boardworks Ltd 2008
  • 2. 2 of 47 © Boardworks Ltd 2008
  • 3. Acids and alkalisHow many examples of acids and alkalis can you spot? 3 of 47 © Boardworks Ltd 2008
  • 4. Acids: true or false? 4 of 47 © Boardworks Ltd 2008
  • 5. Alkalis: true or false? 5 of 47 © Boardworks Ltd 2008
  • 6. Mixing an acid and an alkaliWhat happens when an acid and an alkali are mixed? + ² acid alkaliMixing an acid and an alkali causes a chemical reaction.How could you check that a chemical reaction has taken place? 6 of 47 © Boardworks Ltd 2008
  • 7. Mixing acids and alkalis 7 of 47 © Boardworks Ltd 2008
  • 8. What is neutralization?The chemical reaction between an acid and an alkali is calledneutralization.What is the pH value of the mixture of salt and water? + ² acid alkali salt + waterThe mixture of salt and water is neutral, so its pH is 7.The chemical reaction between an acid and an alkali can bewritten as: acid + alkali ² salt + water 8 of 47 © Boardworks Ltd 2008
  • 9. Neutralizing stingsBee stings are acidic. Wasp stings are alkaline. Which safe household Which safe household substances could you substances could you use to treat a bee sting? use to treat a wasp sting? 9 of 47 © Boardworks Ltd 2008
  • 10. Separating a salt 10 of 47 © Boardworks Ltd 2008
  • 11. Making saltsThe salt produced by a neutralization reaction depends on theacid and the alkali used.Sodium chloride is produced by the reaction betweenhydrochloric acid and sodium hydroxide. hydrochloric sodium sodium acid + hydroxide ² chloride + waterWhich acid and which alkali would be needed to make thesalt potassium chloride?hydrochloric potassium potassium acid + hydroxide ² chloride + water 11 of 47 © Boardworks Ltd 2008
  • 12. Naming salts When an alkali reacts with hydrochloric acid, the salt produced is a chloride. When an alkali reacts with sulfuric acid, the salt produced is a sulfate. When an alkali reacts with nitric acid, the salt produced is a nitrate.Which acid would be needed to make these salts?2. copper nitrate3. magnesium chloride4. sodium sulfate 12 of 47 © Boardworks Ltd 2008
  • 13. Making salts: word equationsComplete these word equations:hydrochloric potassium potassium acid + hydroxide ² chloride + water sodium sodiumsulfuric acid + hydroxide ² sulfate + water potassium potassium nitric acid + hydroxide ² nitrate + water 13 of 47 © Boardworks Ltd 2008
  • 14. Making salts: completing equations 14 of 47 © Boardworks Ltd 2008
  • 15. Making salts: symbol equationsComplete these symbol equations:hydrochloric potassium potassium acid + hydroxide ² chloride + water HCl + KOH ² KCl + H2O potassium potassium nitric acid + hydroxide ² nitrate + water HNO3 + KOH ² KNO3 + H2O magnesium magnesiumsulfuric acid + hydroxide ² sulfate + water H2SO4 + Mg(OH)2 ² Na2SO4 + 2H2O 15 of 47 © Boardworks Ltd 2008
  • 16. Balancing equationsWhen a chemical reaction occurs, it can be described by aa symbol equation.The balanced symbol equation for a chemical reaction showsthe ratio of reactants and products involved. For example: sodium sodiumsulfuric acid + hydroxide ² sulfate + water H2SO4 + 2NaOH ² Na2SO4 + 2H2OAn ‘unbalanced’ equation can be balanced by multiplyingthe different atoms and molecules on each side by differentamounts, so that they match. 16 of 47 © Boardworks Ltd 2008
  • 17. Balancing equationsIf you count the number of atoms of each type on each sideof this equation, you will see that they do not match. H2SO4 + NaOH ² Na2SO4 + H2OSo, multiply the sodium atoms on the left by 2: H2SO4 + 2NaOH ² Na2SO4 + H2ONow that the number of sodium atoms on each side is equalthe number of hydrogen atoms on the left side has increased.So multiply the number of hydrogen atoms on the right by 2. H2SO4 + 2NaOH ² Na2SO4 + 2H2O 17 of 47 © Boardworks Ltd 2008
  • 18. Balancing equations for making salts 18 of 47 © Boardworks Ltd 2008
  • 19. Indigestion remediesThe acid in your stomach that helps you break down your foodis called hydrochloric acid. It has a pH of between 1 and 2.Indigestion and heartburn are causedby an excess of acid in your stomach.Indigestion remedies suchas Milk of Magnesia containantacids, like magnesiumoxide and calcium carbonate.What do you think antacids doto the acid in your stomach? 19 of 47 © Boardworks Ltd 2008
  • 20. 20 of 47 © Boardworks Ltd 2008
  • 21. Metal oxideMetal oxides are compounds made from a metal and oxygen.For example, burning magnesium in oxygen producesmagnesium oxide. magnesium + oxygen ² magnesium oxideAcids react with metal oxides to make a salt and water.For example, sulfuric acid reacts with copper oxide to makecopper sulfate and water. copper coppersulfuric acid + oxide ² sulfate + water 21 of 47 © Boardworks Ltd 2008
  • 22. Base or alkali?Bases are substances thatreact with acids, which includemetals oxides, hydroxides and bases: reactcarbonates. with acidsAlkalis are substances that alkalis:react with acids and which soluble inare soluble in water. waterCopper oxide is a base, but not an alkali, because it reactswith acids, but does not dissolve in water.Sodium hydroxide is an alkali (and a base), because it reactswith acids and it is soluble in water. 22 of 47 © Boardworks Ltd 2008
  • 23. Acids and metal oxides 23 of 47 © Boardworks Ltd 2008
  • 24. Making copper sulfate 24 of 47 © Boardworks Ltd 2008
  • 25. Metal oxides + acids 25 of 47 © Boardworks Ltd 2008
  • 26. What is the formula? 26 of 47 © Boardworks Ltd 2008
  • 27. FormulaeHow do we know that the formula of sodium chloride is NaCl,while the formula of copper chloride is CuCl2?It is because of the combining power of the atoms. Sodium has a combining power of 1, so it bonds with one other atom. Chlorine also has a combining power of 1, so it bonds with one other atom. Copper, though, has a combining power of 2, so it needs to bond to two chlorine atoms.The formula of magnesium chloride is MgCl2, so what do youthink is the combining power of magnesium? 27 of 47 © Boardworks Ltd 2008
  • 28. Formulae and combining powersHere are the combining powers of some metal and non-metalatoms: combining non-metal combining metal atom power atom power Na 1 Cl 1 K 1 F 1 Mg 2 O 2 Cu 2 N 3 28 of 47 © Boardworks Ltd 2008
  • 29. Formulae and combining powers 29 of 47 © Boardworks Ltd 2008
  • 30. 30 of 47 © Boardworks Ltd 2008
  • 31. Acid and carbonateWhen a carbonate reactswith an acid, it gives offcarbon dioxide gas.How could you test thegas given off, to confirmthat it is carbon dioxide?What would youobserve in this test? carbon dioxide limewater 31 of 47 © Boardworks Ltd 2008
  • 32. Acid and carbonateThe products of the reaction between a carbonate and anacid are a salt, carbon dioxide and water.Calcium carbonate is a substancethat is naturally found in the shellsof sea creatures and snails.What salt do you think will be produced by the reaction ofhydrochloric acid and calcium carbonate?hydrochloric calcium calcium carbon acid + carbonate ² chloride + dioxide + water 32 of 47 © Boardworks Ltd 2008
  • 33. Reaction of carbonates 33 of 47 © Boardworks Ltd 2008
  • 34. Acid and metalAcids also react with metals to make a gas.When an acid reacts with a metal, the gasproduced makes a lighted splint go pop.What is this gas?A salt is also produced during thereaction. What is the name of the saltthat will be produced by the reactionof hydrochloric acid with calcium? hydrochloric calcium acid + calcium ² chloride + hydrogen 34 of 47 © Boardworks Ltd 2008
  • 35. Choose your reactionSome metals react violently with acids, so it wouldn’t be safeto use them to make a salt in the classroom.However, if you still wanted to make that salt, you could usethe metal carbonate instead.Sodium reacts very violently with sulfuric acid, so should notbe uses to make sodium sulfate. However, you could safelyuse sodium carbonate.sulfuric sodium sodium carbon acid + carbonate ² sulfate + dioxide + waterCould you safely use sodium hydroxide to make sodiumsulfate? What about sodium oxide? 35 of 47 © Boardworks Ltd 2008
  • 36. Choose your reaction 36 of 47 © Boardworks Ltd 2008
  • 37. What is acid rain?Rainwater has a pH of about 5.6, whichmeans that it is naturally slightly acidic.This natural acidity is due to carbondioxide in the air dissolving into the rain,forming a weak acid called carbonic acid.Rainwater with a lower pH than normalis called acid rain.Burning of fossil fuels in power stations and cars formspollutants such as sulfur dioxide and nitrogen oxides.These gases dissolve in rainwater to make sulfuric acid andnitric acid, which are strong acids, so also form acid rain.Why is acid rain a serious environmental problem? 37 of 47 © Boardworks Ltd 2008
  • 38. How does acid rain work? 38 of 47 © Boardworks Ltd 2008
  • 39. Effects of acid rainAcid rain has many damaging effects on the environment: The acids in acid rain speed up the chemical weathering of rocks and buildings. Rivers, lakes and streams become more acidic so that animals and plants cannot live in them. Soil that becomes more acidic has fewer nutrients so trees and other plants cannot grow. Acid rain also damages trees by breaking down the waxy coating of leaves.What can be done to reduce acid rain and its effects? 39 of 47 © Boardworks Ltd 2008
  • 40. Reducing acid rainGovernments are working to reduce the emissions of theacidic pollutants produced by burning fossil fuels. Sulfur dioxide is formed when coal containing sulfur is burned in power stations. This acidic pollutant can be removed from the gases before they are released into the atmosphere. Nitrogen oxides are formed when petrol burns in a car’s engine. Exhaust systems can be fitted with a catalytic converter which turns harmful gases into harmless gases.How do these changes help to reduce acid rain? 40 of 47 © Boardworks Ltd 2008
  • 41. Acid rain – a global problemForests in Scandinavian countries such as Sweden havesuffered greatly from the damaging effects of acid rain. However, scientists have shown that the acid rain that falls in Sweden is not produced there. The source of the acidic pollutants is in fact more likely to be UK factories and power stations. This happens because air pollution can be carried high up into the sky, where it is pushed by strong winds towards other countries.Is it right that a country can directly cause pollution in another? 41 of 47 © Boardworks Ltd 2008
  • 42. Should pollution be contained? 42 of 47 © Boardworks Ltd 2008
  • 43. Limiting the effects of acid rain: opinions 43 of 47 © Boardworks Ltd 2008
  • 44. 44 of 47 © Boardworks Ltd 2008
  • 45. Glossary 45 of 47 © Boardworks Ltd 2008
  • 46. Anagrams 46 of 47 © Boardworks Ltd 2008
  • 47. Multiple-choice quiz 47 of 47 © Boardworks Ltd 2008