Water HardnessReview its causes

Identify cations causing hardnessClassify differnet types of harness

Observe its effects – harmful and beneficialUnderstand procedures to remove water hardness

Title: Hard and Soft WaterObjectives• – 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?

SOAP

SCUM

PermanentHardwaterMinerals (Salts)

Water hardness in the UK by regionWhere will your kettle last the longest?

YorkshireCheshire

Peak DistrictMalvern

SomersetCornwall Guildford

LO – to describe key features of hard and soft water. - To explain how to identify hard and soft waters

Temporary Hard water = Ca(HCO3)2 or Mg(HCO3)2

SOAP

SCUM

Does furring in kettles occur in all types of water? B – what is needed for this reaction?

Calcium calcium + carbon carbonate oxide dioxide

Install a water softener

Na+

Ca2+

Mg2+

Na2CO3

Sodium CarbonateCalcium ions + Sodium Carbonate

Sodium ions + Calcium Carbonate

The Water CycleQ - 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.

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)

Titel: Temporary and Permanent Hard WaterLernziel• 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

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

Review – explaining how temporary hard water is softened by boiling

Choice 1Explain which ions are missing from soft water

Choice 2Explain the symbol equation for the reaction of calcium ions with carbonate to form scale in full sentences.

Choice 3Write a balanced symbol equation for the reaction of Magnesium ions with carbonate ions to form scale

CompulsoryWrite definitions for these key wordsPermanent 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