4 pictures 1 word : link?. learning objectives content identify how water becomes hard start to...
TRANSCRIPT
4 pi
ctur
es 1
wor
d : l
ink?
BIG PICTURE
What is the most expensive natural commodity?
Lear
ning
Obj
ectiv
es 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 waterSkill• Observation and measuring skillsBenefit• Explain why you will need more shampoo when
you go to London!• How some hard water maybe good for your health
Beco
min
g ha
rd!
Water as part of the water cycle is slightly acidic (CO2 from atmosphere forming carbonic acid, H2CO3(aq) and naturally comes into contact with rocks ...
Compounds of the rock then dissolve into the water.
Beco
min
g ha
rd!
limestone
So what is in limestone?
So what is in dolomite?dolomiteCaCO3
MgCO3 and CaCO3
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 (SO4)in rocks as well as carbonates
Becoming hard!So what would the reaction be for limestone?
EXTENSIONSo what would the reaction be for dolomite?
What are the reactants? Don’t forget
state symbols!
H2CO3(aq) + CaCO3(s) → Ca(HCO3)2(aq)
carbonic acid + calcium carbonate → calcium hydrogencarbonate
Start with word equation
Forms - calcium hydrogencarbonate
Obs
erva
tion
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 Type HP SW HT BT
Foam height (cm3)
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 (HCO3-), which when heated decompose into carbonate ions (CO3
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 waterI 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 + Ca2+ calcium stearate + Na+
soap + hardwater scum + soluble ions
Evaluate hard and soft water ......
Soft PermanentHard
Temporary Hard
STUCK???
Minerals involved?
Advantages of this water?
Made by?
REALLY STUCKOR 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?
So back to bubbles .....