C11 Air and Water

1. A jellyfish and a cucumber are each 85% water.
2. Water expands by 9% when it freezes.
3. 70% of the human brain is water

C11 Air and Water

There are 2 truths and 1 lie. Which one is the lie?

Do Now

1. 30% of fresh water is in the ground.
2. 3% of the earth's water is fresh.
3. Unsafe water kills 100 children every hour.

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C11 Air and Water

There are 2 truths and 1 lie. Which one is the lie?

Do Now

1. Water makes up about 66 percent of the human body
2. A swimming pool naturally loses about 2785 litres a month to evaporation.
3. There is about the same amount of water on Earth now as there was millions of years ago.

C11 Air and Water

There are 2 truths and 1 lie. Which one is the lie?

Do Now

In your book, write the equation for CuSO₄ and CoCl₂ combining with water

How is this a test for water?

Name 4 uses of water

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C11 Air and Water

Describe a chemical test for water using copper(II) sulfate and cobalt(II) chloride

https://www.youtube.com/watch?v=83YWAMhC2VI

https://www.youtube.com/watch?v=YGdArTxQVq0

Pretend you are a scientist and you need to teach other scientists how to test for water

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C11 Air and Water

Role Play

Describe a chemical test for water using copper(II) sulfate and cobalt(II) chloride

1. Design a water purifying system with the equipment in the room.
2. You have 10 minutes to design and build your device
3. Then we test them with dirty muddy water
4. What other steps are needed to make this drinkable?
5. Draw, label and explain your design

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C11 Air and Water

Describe, in outline the treatment of the water supply in terms of filtration and chlorination

Challenge:

https://www.youtube.com/watch?v=rXepkIWPhFQ

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C11 Air and Water

1. State 3 things that are likely to be wrong with this water
2. Suggest how you could remedy each of these problems

C11 Air and Water

Instructions for Market Place Activity

Describe, in outline the treatment of the water supply in terms of filtration and chlorination

1. Split into small groups.
2. Each group is provided detailed information regarding 1 aspect of how water is made safe to drink
3. You have 10mins to make a poster/diagram conveying as much information on your sheet as possible
4. You can not use more than 15 words (excluding the title), but you can use as many chemical symbols and numbers as you like

C11 Air and Water

You have 2mins per poster to capture as much information as possible

Describe, in outline the treatment of the water supply in terms of filtration and chlorination

1. You have 5mins to make a poster/diagram conveying as much information on water filtration as possible
2. You can not use more than but you can use as many chemical symbols and numbers as you like

https://www.youtube.com/watch?v=KMP9-49I1U4

C11 Air and Water

Coagulation

Describe, in outline the treatment of the water supply in terms of filtration and chlorination

Adding Aluminium Sulphate (Alum) causes clay, dirt and other organic matter to clump together to form large particles of floc.

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The floc settles to the bottom of the tank under gravity.

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This helps the subsequent removal of particles by sedimentation and filtration.

The coagulant Aluminium Sulphate is added

This causes impurities to clump or coagulate together

Impurities sink to the bottom as “floc”

C11 Air and Water

Flocculation and Sedimentation

Describe, in outline the treatment of the water supply in terms of filtration and chlorination

The large tanks allow the floc to settle to the bottom as sludge under gravity.

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The water spends a total of about 5 hours in the tank. The flow is continuous.

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The dripping of the water into the tank allows extra oxygen to mix with the water.

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This provides more oxygen for microbial respiration in bacteria which are responsible for decomposing organic matter that enters the sedimentation tank.

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C11 Air and Water

Filtration

Describe, in outline the treatment of the water supply in terms of filtration and chlorination

This is the final step in removing suspended particles and any unsettled floc

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Water moves through a layer of charcoal or coal before being further filtered by the sand. This acts as an excellent microfilter, trapping air which again increases available oxygen for microbial respiration, thus helping decomposition

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Most particles pass through surface layers but are trapped in pore spaces or stick to sand particles.

Relatively clean water leaves the filtration bed

C11 Air and Water

Disinfection and Fluoridation

Describe, in outline the treatment of the water supply in terms of filtration and chlorination

The disinfection of water by adding chlorine gas is called chlorination. Chlorine was used for the first time in 1850 when John Snow used it in London’s water system to combat cholera.

This has resulted in a significant decrease in the number of deaths caused by cholera, typhoid, diarrhoea and hepatitis A. Today, chlorination is used to treat most of drinking in the world since it is easy, inexpensive and reliable.

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Fluorine is also added to water to strengthen teeth. This prevents tooth decay. Some people are against the fluoridation of because they believe it could be linked to cancer and tooth flecking. Scientists are divided as there seems to be insufficient evidence and no difference in levels of cancer in fluoridated and unfluoridated areas

C11 Air and Water

Plenary

Describe, in outline the treatment of the water supply in terms of filtration and chlorination

Questions of water safety

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1. State 3 things that make water unfit to drink

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• List the stages involved in water purification

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• Why is chlorine added to water?

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• Why is fluorine added to water?

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• Why do some people campaign against the fluoridation of water?

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• What is sedimentation and why is it useful?

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• How does aluminium sulphate help sedimentation

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• Why is unclean water dripped slowly over large filter beds at sanitation plants

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Water Purification

1. What percentage of the Earth’s water is drinkable
2. What percentage of the Earth’s drinkable water is locked in Icecaps and glaciers
3. What percentage of this is accessible(surface water)?
4. What percentage of the Earth’s fresh water is found in lakes
5. And what percentage is found in rivers?
6. Much of the drinking water in Saudi Arabia is obtained by distillation of sea water. Explain why this is not an option for a country like Zimbabwe
7. Suggest a reason why each of the following might be found in drinking water: Nitrates, Lead and Pesticides

Why don’t we just evaporate sea water on an industrial scale to make fresh drinkable water?

C11 Air and Water

Water purification

Describe, in outline the treatment of the water supply in terms of filtration and chlorination

Homework

Find out how water filters containing carbon and silver ions are used as exchange resins to remove dissolved particles to improve the taste of water

C11 Air and Water

Homework

Describe, in outline the treatment of the water supply in terms of filtration and chlorination

• Combustion is another name for burning.
• It is an example of an exothermic reaction, a reaction that releases energy to the surroundings.
• This is mostly thermal energy, but light energy and sound energy are also released.
• The fire triangle shows the three things needed for a fire to start and keep going.

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C11 Air and Water

Combustion

Task 1:

1.

2.

3.

4.

5.

6.

7.

8.

Challenge: What were the 8 words covered up?

How you would stop combustion in each scenario?

C11 Air and Water

Discuss the following scenarios with the person next to you.

Task 1:

1.

Challenge: What part of the ‘combustion triangle’ needs to be removed for each scenario?

2.

3.

4.

5.

6.

• methane + oxygen → water + carbon dioxide
• CH₄ + 2O₂ → 2H₂O + CO₂

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• the hydrogen atoms are rearranged to combine with oxygen to make water vapour, H₂O
• the carbon atoms are rearranged to combine with oxygen to make carbon dioxide, CO₂

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C11 Air and Water

Draw the reactants and products of combustion

Task 1:

Challenge: Annotate the products