1. Water H2O What do the students think of when they see this picture?
Where do we find water? Rivers/Lakes/Oceans/Streams etc.

2. Test for Water Cobalt Chloride Cobalt Chloride Paper Paper
Click on slide to drop water onto blue cobalt chloride paper and it turns pink.

3. 3 States Solid 0˚C Room Temperature 100˚C Liquid Gas
Water exists in all three states (phases).
Ask the students if they know at what temperature water is present in it’s solid/liquid/gas phase. i.e. question them to see if they know the freezing point and boiling points of water.
Click on the slide to reveal the names.
A further click shows up the temperatures at which the water exists in these phases.
Solid
0˚C
Room Temperature
Liquid
Gas
100˚C

4. Properties of Water
Water is the only liquid that expands when it freezes
Ice is less dense than water
Ice floats on top
Water is an excellent solvent
Ask question why does ice float on top?
What would you expect a solid to do?
Click to add picture of ice
Can the students name a solute that is not soluble in water? i.e. oil non-polar substances.
Oil in water forms an immiscible solution. =
NaCl +
Solvent
Solution

5. Water, Water Everywhere!
Covers 70% of Earth’s surface
Human body is 2/3 water
Click to add man

6. 70% of the earth is covered in water but only a small percentage~ 3% is accessible.
Water is essential for life!
Click on the page to reveal the pie charts.

7. Water Cycle Water is recycled - Constant supply
Evaporation =Turning a liquid into a gas
Transpiration = Loss of water from the stomata of a leaf
Click on page to reveal definitions.
Stomata

8. Water Cycle

9. Water as a solvent Tap water contains : - dissolved gases
- dissolved solids
- suspended (floating) solids
How do fish breathe underwater?
Dissolved oxygen

10. To Show that Water Contains Dissolved Solids
Water sample
Clock glass
Water
Wire gauze
Water is such a good solvent it contains many dissolved solids.
Test various water samples using the apparatus as pictured above to determine what dissolved solids they may contain.
Test a sample of hard water, soft water, rain water, a stream sample etc.
Click on the green question box and it will link to assessment 1.
Bunsen burner
Tripod

11. Water Hardness Hard Water Soft Water Scum Bubbles
Soft water forms bubbles easily with soap
Hard water does not form bubbles easily with soap
Ask students as to what type of water is in their area?
If they live near a limescale area e.g. Burren they will have hard water.
Scum
Bubbles

12. What causes water hardness?
Calcium ions dissolved in the water
Calcium Carbonate + Rainwater Calcium ions in solution
CaCO H2CO Ca(HCO3)2
(insoluble) (carbonic acid) (soluble)
Burren
Calcium carbonate is present in limestone areas.
Water that contains dissolved Carbon dioxide gas forms carbonic acid
The acid dissolves the calcium carbonate to form calcium hydrogen carbonate which dissolves in the water.
Students should know the reaction of an acid and a carbonate .

13. What causes water hardness?
Soluble compounds of calcium and magnesium
Calcium Hydrogen Carbonate = Ca(HCO3)2
Magnesium Hydrogen Carbonate = Mg(HCO3)2
Calcium Sulphate = CaSO4
Magnesium Sulphate = MgSO4
Click on page to reveal the soluble compounds

14. To test various water samples for hardness
Soap Solution
Using the apparatus above add a little soap solution to various water samples in order to determine how easily they form bubbles.
A B C D

15. 2 Types of Water Hardness
1. Temporary Hardness
Can be removed by boiling
Caused by : Ca(HCO3)2
Mg(HCO3)2
2. Permanent Hardness
Cannot be removed by boiling
Caused by : CaSO4
MgSO4
Click to reveal the compounds that cause temporary and permanent hardness.

16. Temporary Hardness Boil Removed by boiling Problem: CaCO3 Ca(HCO3)2
The problem with boiling the water is that while the temporary hardness is removed the CaCO3 formed precipitates out of the solution to leave a scale on pipes and kettles.
CaCO3
Ca(HCO3)2
Boil
Insoluble
(Limescale)

17. Permanent Hardness X Cannot be removed by boiling
Can be removed by adding softeners
Can be removed by passing water through an ion exchange resin
ion exchange resin

18. Water Softeners Easy method NaCO3 + CaSO4 CaCO3 + NaSO4 Bath salts
- Add Sodium Carbonate (Washing Soda) NaCO3
NaCO3 + CaSO4 CaCO3 + NaSO4
does not make water hard
insoluble
Click to reveal a picture of bath salts
Bath salts
coloured NaCO3

19. Ion Exchange Hard tap water ion exchange resin glass wool plug
Apparatus required to deionise hard water.
Click on black square to reveal movie of ion exchange
Soft water

20. Ion exchange
Positive Ca2+ ions in the water swapped for H+1 ions in the resin
Negative ions in water replaced by OH- ions in the resin
H+ ions and OH- ions Water (H2O)
Deionised water
Click on page to allow movement of ions between the resin and the water.
Ion exchange resins are specially prepared plastic beads.
Ca2+ H+
HCO3-
OH-
Hard water
Resin

21. Advantages of Hard Water Disadvantages of Hard Water1.
Good for brewing
Ca needed for healthy teeth and bones
Tastes better
Blocks pipes and leaves a scale on kettles and boilers
Wastes Soap
Makes scum with soap
Click on page to reveal the advantages and disadvantages one by one.

22. Advantages of Hard Water Disadvantages of Hard Water
Ca for healthy teeth and bones
1. Limescale -blocks pipes and leaves a scale on kettles.
2. Good for Brewing
2. Wastes soap
3. Tastes better
3. Scum produced with soap
As before.

23. Pure Water Distilled water Chemical experiments Car batteries
Wash Bottle
Click on the green square to reveal assessment questions.

24. To obtain pure water from seawater
Water out
Liebig condenser
Ask the students if they can list what type of dissolved substances seawater may contain?
Click on the green button to reveal assessment questions
Water in
Seawater
Pure water
Bunsen

25. Would you drink this water?
Why would the students not drink this water?
The colour is off-putting. There may be suspended solids floating in the water. Bacteria and diseases such as typhoid.
Would the students drink the water in the second picture?
Why is this water more appealing?

26. 6 Steps in Water Treatment
Screening
Sedimentation
Filtration
Chlorination
Fluoridation
pH adjustment
Click to reveal the 6 steps
Note in the picture the difference between the two water samples

27. Water Treatment Process

28. 1. Screening 2. Sedimentation Water is stored in large settling tanks.
Removal of large pieces of dirt and rubbish.

29. 3. Sedimentation 4. Filtration
Flocculating agent added e.g. Alum that forces small dirt particles to clump together.
Very small particles are removed when water is passed through the filtration beds.

30. 4. Chlorination 5. Fluoridation
Cl2 F2
Note: The students have heard about chlorine at the swimming pool.
The students know that fluoride is added to toothpaste.
Chlorine gas is added to kill any bacteria.
Fluorine compounds are added to help prevent tooth decay.

31. 6. pH adjustment
Lime
Lime is basic and so it raises the pH of the water
Lime is added to acidic water to increase the pH.

32. H2O H H
Bonds join the H atoms to the O atom O

33. Breaking Bonds Electrolysis Cannot break the H20 molecules by heating
Have to break the bonds joining the oxygen and the hydrogen atoms to free the atoms
Electrolysis
H2O H+ + OH-

34. Electrolysis of Water
Electrolysis is the production of a chemical reaction by electricity
An electrolyte is a solution that conducts electricity by the movement of ions
Sulphuric acid (H2SO4) is added to the water to help it to conduct electricity
Breakdown water into it’s elements

35. Electrolysis of Water Hoffmann Voltammeter Acidified water Oxygen
Hydrogen
Cathode
Anode
Battery

36. Electrolysis of Water -Test for oxygen gas?
H2 collects at the negative electrode (cathode)
-Test for hydrogen gas?
O2 collects at the positive electrode (anode)
-Test for oxygen gas?
Result:
Twice as much hydrogen as oxygen is produced
Conclusion:
H2O molecule
2 hydrogen atoms for every 1 oxygen atom

37. H20 Molecule 1Oxygen atom 1 Hydrogen atom 1Hydrogen atom H H O
Click on the page to form the water molecule
1 Hydrogen atom
1Hydrogen atom
1Oxygen atom

38. Assessment for lesson 1 What is the test for water?
What is the freezing point of water?
Describe an experiment to investigate dissolved solids in a water sample.
Outline an experiment to determine the amount of hardness in a water sample.

39. Assessment for lesson 2 What is hard water?
What causes water hardness?
Name the two types of water hardness?
How are they removed?
What happens when hard water is passed through an ion exchange resin?

40. Assessment for lesson 3
What might you find dissolved in a sample of sea water?
Outline an experiment to obtain a sample of pure water from sea water.
Label diagram

41. Assessment for lesson 4 Why do we treat our drinking water?
List the six steps in water treatment?
Why is chlorine added to our the water?
Where else have you seen chlorine added to water?
Why is fluorine added to our drinking water?
Where else have you seen fluorine added?

42. Assessment for lesson 5 What is electrolysis?
Name the apparatus used to electrolyse water?
What are the anode and the cathode?
What are the results of the electrolysis experiment?
What does the electrolysis experiment prove?