Chemistry My family and home 03/07/2015

Acids and bases (alkalis) Used by the body, used in other processes: such as food, farming and chemical industries. 03/07/2015

Chemistry Lesson Safety in chemistry Acids and alkalis (bases) Neutralisation Using indicators Practical work 03/07/2015

Hazard signs to learn… hi flammable HarmfulIrritant Corrosive

03/07/2015 Hazard signs to learn… Radioactive Oxidising Dangerous for environment Toxic

Safety Irritant- can cause a rash or itching Harmful-general damage to living organisms Corrosive-will burn through materials 03/07/2015

Safety instructions Wear goggles Follow safety instructions 03/07/2015

Acids and bases Acid- A substance that produces hydrogen ions (H + ) when it dissolves in water. Bases- Compounds which react with acids to neutralise them Alkali- A soluble base, forms hydroxide OH - ions in water. Neutral-not an acid or base 03/07/2015

Symbols in word equations -states of matter (l) liquid (g) gas (s) solid (aq) aqueous-dissolved in water 03/07/2015

Acids and bases (alkalis) 03/07/2015

Acid Examples of acids include : Vinegar, orange or lemon juice, acid rain, stomach acid, nitric acid, sulfuric acid, hydrochloric acids Used in car batteries, food and drinks, preserving food, in body. 03/07/2015

Acid Hydrochloric acid is formed when hydrogen chloride is gas dissolves in water. HCl (g)  H + (aq) + Cl - (aq) 03/07/2015

Alkali (bases) Examples and uses include: metal hydroxides, metal oxides, cleaning products, stomach antacids, baking powder. 03/07/2015

Alkali Sodium hydroxide is formed when the solid is dissolved in water. NaOH (s)  Na + (aq) + OH - (aq) 03/07/2015

What is an acid? Is an alkali (OH or H) Give a use of an acid 03/07/2015

1.An Indicator is a dye that changes colour 2.Indicators can be used to find out whether a solution is acid, alkaline or neutral 3.Universal Indicator can be used to find the pH of a solution Acid – red, pH less than 7 Neutral – green, pH = 7 Alkali – blue, pH greater than 7 pH scale

03/07/2015 Universal Indicator and the pH scale Strong acid Strong alkali Neutral Universal Indicator is a mixture of liquids that will produce a range of colours to show how strong the acid or alkali is: 0-14 Stomach acidLemon juiceWaterSoapOven cleanerBaking powder 0

pH scale

Practical 1 Test chemicals to find pH Use paper and liquid Record results in a table 03/07/2015

1.Acids react with alkaline solutions to form a salt and water Hydrochloric acid produces chlorides Nitric acid produces nitrates Sulphuric acid produces sulphates 2.Ammonia can dissolve in water to produce an alkaline solution. This can be neutralised with acids to produce ammonium salts 3.Indicators can monitor neutralisation reactions Neutralisation Neutralisation

03/07/2015Neutralisation An acid and alkali will neutralise each other (if the correct amounts are used): Acid + alkaliSalt + water Acid + base  Salt + water E.g. hydrochloric acid + sodium hydroxidesodium chloride + water

Neutralisation Acids and bases neutralise each other. Acids form H + (aq) ions in water Alkalis form OH - (aq) ions in water Acid + alkali  salt + water H + + OH -  H 2 O The other parts form the salt. 03/07/2015

Neutralisation – Hydrochloric acid Neutralisation

Neutralisation – Sulphuric acid Neutralisation

Neutralisation – Nitric acid Neutralisation

Questions Write a word equation for adding hydrochloric acid to magnesium hydroxide Extension : Write a balanced symbol equation for this reaction (difficult) Hint Mg(OH) 2 MgCl 2 03/07/2015

Answers Acid + base  salt + water Hydrochloric acid + Magnesium hydroxide  magnesium chloride and water 2HCl + Mg(OH) 2  MgCl 2 +2H 2 O 03/07/2015

Neutralisation – Fertiliser Neutralisation

Practical 2 Titrations and neutralisation 03/07/2015

Useful acid-alkali reactions 1) Hydrochloric acid is used in the stomach to help _______. If we eat too many “rich” foods our stomachs create too much ____ – this is called ______. This acid needs to be neutralised by taking indigestion tablets. 2) Soil is naturally acidic, mainly due to acid ____. This can have bad effects on ____ and vegetable growth, so the excess acid may need to be neutralised with an _____. Words – plant, digestion, indigestion, alkali, rain, acid

03/07/2015 Quiz on acids and alkalis 1)This a pH of less than 7 2)This would turn Universal indicator green 3)This is often used in cleaners or soap 4)This would turn Universal Indicator red 5)Sodium hydroxide is a common ____________ 6)This would feel soapy on your skin 7)This could be a corrosive 8)This will turn universal indicator purple 9)This would taste sour 10)Lemon juice and vinegar are examples of weak _____ Acid, alkali or both???

Acids and metals Acid + metal  Salt + hydrogen 03/07/2015

Metals and acids The more reactive the metal, the faster the reaction The speed of reaction is indicated by the rate at which bubbles of hydrogen are produced. Test for hydrogen???? Name of salt depends on metal and acid used 03/07/2015

Reaction of Metals and Acid

Hydrochloric acid Produces Chloride salts Magnesium + Hydrochloric acid  Magnesium Chloride + ________ _______ + Aluminium +Aluminium Chloride + __________ ________+ ________  Zinc chloride + _________ 03/07/2015

Hydrochloric acid Produces Chloride salts Magnesium + Hydrochloric acid  Magnesium Chloride + hydrogen Hydrochloric acid + Aluminium +Aluminium Chloride + hydrogen Hydrochloric acid+ zinc  Zinc chloride + hydrogen 03/07/2015

Symbol equations 2HCl + Mg  MgCl 2 +H 2 ____HCl + 2Al  2AlCl 3 + 3H 2 2____ + ____  ZnCl 2 + H 2 03/07/2015

Symbol equations 2HCl + Mg  MgCl 2 +H 2 2HCl + 2Al  2AlCl 3 + 3H 2 2HCl + Zn  ZnCl 2 + H 2 03/07/2015

Sulfuric acid reactions H 2 SO 4 + ______  MgSO 4 + H 2 3H 2 SO 4 + 2Al  Al 2 (SO 4 ) 3 + 3H 2 H 2 SO 4 +Zn  ZnSO 4 + H 2 Copy and complete write a word equation for each. 03/07/2015

Sulfuric acid reactions H 2 SO 4 + Mg  MgSO 4 + H 2 3H 2 SO 4 + 2Al  Al 2 (SO 4 ) 3 + 3H 2 H 2 SO 4 +Zn  ZnSO 4 + H 2 Sulfuric acid + magnesium  Magnesium sulfate + hydrogen 03/07/2015

Nitric acid Nitric acid reacts with alkalis, but when reacting with metals it can produce nitrogen oxides. 03/07/2015

1.Transition metal oxides and hydroxides do not dissolve in water. They are called bases 2.They react with acids to produce salts that are soluble 3.The excess metal oxide can be filtered off Metal Oxides & Hydroxides

Metal hydroxide Metal hydroxide + acid  salt + water 03/07/2015

Metal oxide Metal oxide + acid  salt + water 03/07/2015

Adding acid to carbonates Carbonates are compounds containing carbon and oxygen. When an acid is added to a carbonate the carbonate starts to fizz. A gas called _________ _______ is produced. Calcium carbonate + hydrochloric acid calcium chloride + carbon dioxide + water CaCO 3(s) + HCl (aq) CaCl 2(aq) + CO 2(g) + H 2 O (l) 2

Metal carbonate Metal carbonate + acid  water + salt + carbon dioxide 03/07/2015

Quiz Quiz