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Hard water and soft water full lesson
- 1. Water Hardness Review its causes Identify cations causing hardness Classify differnet types of harness Observe its effects – harmful and beneficial Understand procedures to remove water hardness
- 2. Title: Hard and Soft Water Objectives • – describe key features of hard and soft water. • - explain how to identify hard and soft waters Starter – What has happened to these kettles and this bathroom?
- 17. Water hardness in the UK by region Where will your kettle last the longest? Yorkshire Cheshire Peak District Malvern Somerset Cornwall Guildford LO – to describe key features of hard and soft water. - To explain how to identify hard and soft waters
- 19. Temporary Hard water = Ca(HCO3)2 or Mg(HCO3)2
- 22. S O A P S C U M
- 36. Does furring in kettles occur in all types of water? B – what is needed for this reaction? Calcium calcium + carbon carbonate oxide dioxide
- 42. Ca2+ Mg2+ Na2CO3 Sodium Carbonate Calcium ions + Sodium Carbonate Sodium ions + Calcium Carbonate
- 43. The Water Cycle Q - Where in this water cycle does our drinking water come from? Hard water contains dissolved compounds, usually of calcium or magnesium. The compounds are dissolved when acidic water comes into contact with rocks.
- 44. The Water Cycle and water hardness – the chemistry Hard water contains dissolved compounds, usually of calcium or magnesium. The compounds are dissolved when slightly acidic water comes into contact with rocks. CaCO3(s) + H2O(l) + CO2(aq) Ca2+(aq) 2HCO3 -(aq)
- 45. Titel: Temporary and Permanent Hard Water Lernziel • to be able to distinguish between temporary hard water and permanent hard water • To be able to explain what happens when we heat temporary hard water Starter A – Does furring in kettles occur in all types of water? B – what is needed for this reaction? Calcium calcium + carbon carbonate oxide dioxide
- 46. Temporary hard water chemistry this is caused by the presence of CaHCO3 compound – soluble in water LO – to be able to distinguish between temporary hard water and permanent hard water - To be able to explain what happens when we heat temporary hard water Ca2+(aq) 2HCO3 -(aq) CaCO3(s) + H2O(l) + CO2(g) heat (scale)(‘hardness’) Permanent hardness is caused by the presence of soluble Ca2+ and Mg2+ ions in water
- 47. Review – explaining how temporary hard water is softened by boiling Choice 1 Explain which ions are missing from soft water Choice 2 Explain the symbol equation for the reaction of calcium ions with carbonate to form scale in full sentences. Choice 3 Write a balanced symbol equation for the reaction of Magnesium ions with carbonate ions to form scale Compulsory Write definitions for these key words Permanent hard water temporary hard water LO – to be able to distinguish between temporary hard water and permanent hard water - To be able to explain what happens when we heat temporary hard water
Editor's Notes
- Although soaps are excellent cleansers, they do have disadvantages. As salts of weak acids, they are converted by mineral acids into free fatty acids: CH3(CH2)16CO2-Na+ + HCl → CH3(CH2)16CO2H + Na+ + Cl- These fatty acids are less soluble than the sodium or potassium salts and form a precipitate or soap scum. Because of this, soaps are ineffective in acidic water. Also, soaps form insoluble salts in hard water, such as water containing magnesium, calcium, or iron. 2 CH3(CH2)16CO2-Na+ + Mg2+ → [CH3(CH2)16CO2-]2Mg2+ + 2 Na+ The insoluble salts form bathtub rings, leave films that reduce hair luster, and gray/roughen textiles after repeated washings. Synthetic detergents, however, may be soluble in both acidic and alkaline solutions and don't form insoluble precipitates in hard water. But that is a different story...