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Learning Objectives Content Identify how water becomes hard Start to compare and contrast soft water and permanent or temporary hard water Start to evaluate the advantages and disadvantages of soft and hard water Skill Observation and measuring skills Benefit Explain why you will need more shampoo when you go to London! How some hard water maybe good for your health

Becoming hard! Water as part of the water cycle is slightly acidic (CO 2 from atmosphere forming carbonic acid, H 2 CO 3 (aq) and naturally comes into contact with rocks...

Compounds of the rock then dissolve into the water. Becoming hard! limestone So what is in limestone? So what is in dolomite? dolomite CaCO 3 MgCO 3 and CaCO 3 These metals ions (what are these?) are what causes the hardness in water. Describe how hard water is formed and what is found in hard water (D) Sulfates (SO 4 )in rocks as well as carbonates

Becoming hard! So what would the reaction be for limestone? EXTENSION So what would the reaction be for dolomite? What are the reactants? Don’t forget state symbols! H 2 CO 3 (aq) + CaCO 3 (s) → Ca(HCO 3 ) 2 (aq) carbonic acid + calcium carbonate → calcium hydrogencarbonate Start with word equation Forms - calcium hydrogencarbonate

Observation skill! Work in fours, on your table – number yourselves; 1, 2, 3 and 4 1s – collect tubes (HP, SW, HT, BT) & rack 2s – collect syringe/pipette and liquid soap 3s – get a ruler or borrow one 4s – copy out quick table of results Each add EXACTLY TWO DROPS (why exact?) Replace the bung Water TypeHPSWHTBT Foam height (cm 3 )

SHAKE IT OFF! For 1 minute of Taylor – vigorously shake your tubes! 1s & 4s – Write an observed conclusion 2s & 3s – measure the height of foam and fill in table 1s/4s – soap / pipette back 2s/3s – ruler and tube/rack back

What are the different water types? HP – Hard permanent SW – Soft water TP – Temporary hard BT – Boiled temporary What is the difference between temporary and permanent? Temporary contains hydrogencarbonate ions (HCO 3 -), which when heated decompose into carbonate ions (CO 3 2- ), which then go and react with soluble Mg and Ca, forming......

Removing Temporary Hardness Explain how hardness can be removed from temporary and permanent hard water (A/B) Why can't we use this method to remove hardness on a large scale? Form insoluble metal carbonates (limescale), but removing metal ions! Permanent hard water contain sulfates which do not decompose when heated, so metal ions remain

What are the implications of different water types?

Soap lather with soft water Soap lather with hard water I can explain some disadvantages of hard water (C) Hard water makes it difficult to lather soap for washing bodies, dishes and clothes. A lot more soap has to be used with hard water – costing more!

I can explain some advantages of hard water (C) Water from the south west Water from the south east – tastier? What is the difference between these 2 glasses of water?

Limescale means the heating of water is not as efficient - costing more! I can explain some disadvantages of hard water (C)

There is also evidence that heart disease is reduced Promotes healthy teeth and bones Explain some advantages of hard water (C)

Hard water leaves soap scum in baths /sinks/tiles and screens. It is formed when the soap reacts with the ions in the hard water. Explain some disadvantages of hard water (C) sodium stearate + Ca 2+ calcium stearate + Na + soap + hardwater scum + soluble ions

Evaluate hard and soft water......

Soft Permanent Hard Permanent Hard Temporary Hard STUCK??? Minerals involved? Advantages of this water? Made by? REALLY STUCK OR CHECK IF YOU HAVE GOT... Limescale made by ….. Sulfates not carbonates …..

Exam Question Review? Can you complete the question?

How would you make the best bubble/s?