Pitlochry Primary School Online Programme

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Dear Grade 6 Scientists

This week, we are learning about Water Purification. Water is essential for all life on Earth. It is important for us to preserve the quality of the water on Earth. Please click play on the audio links as you work through this task.

I trust that you have completed the activity that was uploaded last week.

Enjoy the following lesson. Remember to always try your best.

Have fun and I hope to see you all soon!

With love, Mrs N Chetty

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Lesson 13

Water PurificationGrade: 6

Presented By: Mrs N Chetty

Pitlochry Primary School Educator 3

Living things such as plants and animals rely on water. Life cann exist without water.The importance of clean waterWater management is everyone’s responsibility but the municipality officials of towns and cities have the responsibility of looking after the water treatment facilities. The municipality must purify water to keep peoplehealthy.

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Thereare four ways to purify water• Boiling• Filtering• Settling and Decanting• Chemical Treatment

Purifying Water

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1. BoilingBoiled water is heated to kill any germs in the water. This method uses a lot of electricity or firewood and does not remove soluble or insoluble pollution.

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2. FilteringPouring water through a funnel and filter paper removes most of the insoluble pollution such as sand but germs can pass through the filter paper. Soluble substances such as chemicals, fertilisers and pesticides are also not removed.

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3. Settling and DecantingWater that is allowed to settle will appear to be clean but not all the insoluble pollutants will settle. Germs and soluble pollutants are not removed.

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4. Chemical TreatmentChemicals can be added to water to kill germs but these chemicals are expensive and can make the water taste awful.

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Draw a table that compares the advantages and disadvantages of each method of water purification listed above.

Activity 13

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Purification Method Advantages Disadvantages

Boiling

Filtering

Settling and Decanting

Chemical treatment

The Story behind tap waterThe Source

A dam is built across a river, water from the dam is pumped to the Water Purification Station.

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1. ScreeningAt the purification station water passes through metal screens to trap large living organisms, sticks, leaves and litter, but allows the rest of the water to pass through it.

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2. Coagulation & FlocculationAll raw water contains suspended particles which need to be removed. Settling of these suspended particles is aided by the adding of chemical coagulants, such as calcium hydroxide.

Coagulation in the Water System is the process which destabilises the particles when the coagulants (slaked lime and sodium silica) are mixed with the raw water. This is the first process in removing suspended particles.

Flocculation is the clumping together of the suspended particles, which were destabilised by coagulation, to form heavier visible particles called floc.

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3. Sedimentation

The water flows slowly into large sedimentation tanks. The flocthen settles to the bottom of the tank to form sludge.

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4. CarbonationAfter sedimentation, the water flows into carbonation bays where it is stabilised by adding pure carbon dioxide gas to the water.

This lowers the pH to between 8,0 and 8.4.

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5. FiltrationThe water passes into the filter houses where it flows through rapid gravity sand filter beds of finely graded silica sand and pebbles.

The remaining suspended particles are removed at this stage.

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6. ChlorinationThe water leaving the purification plant is disinfected with chlorine to kill micro-organisms, bacteria and viruses that may be present in the water.

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Water Supply

This clean water is pumped through underground pipes into reservoirs that supply homes, schools, businesses and factories with clean water.

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Draw a flow diagram explaining how a water treatment facility works

Activity 14

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Reservoir

Dam

Activity 1Question 1

Question 2a) All matter is made up of particles.b) In solids, the particles are closely packed in a regular pattern.c) In gases, the particles are large and far apart.d) In liquids, there are spaces between the particles so they can move around each

other.e) In solids, the particles vibrate in one place.f) In gases, the particles move in all directions.g) In liquids, the particles are small and move around each other.

ANSWERS – Task 1

2020

Activity 2

State what you think the best method to separate each of the following mixtures are:

A – beans and lentils - hand sortingB - flour and rice - sievingC - sand and water - filteringD - oil and water - settling & decanting

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A mixture is a combination of two or more substances that keep their own properties and can easily be separated

A solution is a combination of two or more substances that do not keep their own properties and cannot be easily be separated.They are uniform in appearance.

Beans and samp

coffee

ANSWERS – Task 2 Lesson 3

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properties

own

substances

separated

cannot

hot cocoa

salad

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Filter Strainer

Used to separate a mixture with

larger and smaller particlesExample:

Macaroni and sand

A way to separate liquids but not used as

an easy separation toolExample: Flour

and water

Tweezers

Hand Magnet Evaporation

Used to separate an object out that is attracted to a magnet mixed

with something that is not

Example: Sand and iron filings

Used to separate a liquid or gas

that is mixed with a solid

Example: Sand and water

Used to pick apart mixtures that have

smaller particles that hands would be hard

to separate withExample: Confetti

and rice

Used to pick up and

separate larger objects

Example: Paper clips

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solution mixture

mixturemixture

mixture solution

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5, 6, 8 2, 4, 71, 3

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ANSWERS Task 2 Activity 3

Mixture Appearance of mixture.

Is the solid substance solubleor insoluble?

Is this a homogeneous or heterogeneous mixture?

What method of separating can we use to seperate the 2 compounds?

Water + Mealie meal cloudy suspension insoluble heterogeneous filter

Water + Flour cloudy suspension insoluble heterogeneous filter

Water + Samp whole grains of sampsank to the bottom.

insoluble heterogeneous settle and decant

Water + Sugar uniform appearance

(sugar dissolved)

soluble homogeneous evaporation, crystallization

Water + Jelly Powder uniform appearance

Colour depends on jelly flavor (red, green, yellow

Etc)

soluble homogeneous evaporation

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The substance dissolving into the

liquid or gas

The liquid or gas the substance dissolves into

Able to be dissolved in a liquid or gas

To mix completely with

another substance

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Aim: To separate a homogeneous mixture (salt-water solution)

Hypothesis: If I allow the salt and water solution to stand in the sun, the water will evaporate, leaving salt crystals behind.

Material: fine salt, hot water

ANSWERS TASK 2 - ACTIVITY 4:Separating a homogenous mixture using evaporation

Water vapor

Salt-water solution

Salt particles(solute)

The water, which was the solvent, evaporated,leaving salt particles, which was the solute, behind.

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Answers Task 3 Activity 51. How long did it take for crystals to start forming on

the string? (subject to learners experiment)

2. What are the crystals made of? Sugar

3. Why do you think we boiled the water when dissolving the sugar in the solution?

Boiling the water increases the temperature of the solvent which allows more solute to dissolve.

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Answers Task 3 Activity 61. What is a heterogeneous mixture? It is the combination of two or more substances where, both substances retain their properties and are easily separated. They do not have a uniform appearance.

2. Which separation method worked the best?Filtering

3. What could we add to the funnel to improve filtration? (ie. to remove more sand particles from water)

a layer of gravel and fine sand, additionalcotton wool

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Answers Task 3 Lesson 71. What is this process called? It is called filtration.

2. Why do the sand grains stay behind on the filter paper, but the water passesthrough it?The sand particles are too large to pass through the filter paper.

3. What was the mixture of sugar and water called? (Hint: It was a special kind ofmixture called a.. ?) solution / homogeneous mixture

4. What would happen if the mixture of sugar and water is poured through a filter? The sugar has dissolved in the water, the sugar particles are dispersed among the water particles, the sugar particles will pass through the filter paper along with the water.

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5. Would it be possible to separate the water and the sugar?Yes, by allowing the water to evaporate, the sugar will crystallize.

6. What happens to the sugar when it dissolves in the water?The solute(sugar) particles are dispersed between the solvent (water)particles.

7. Why is it not possible to separate a solution through a filter?The solute particles are dispersed among the solvent particles. Both particles will be small enough to pass through the filter paper.

8. Describe how you can get the solid sugar back from the sugar solution.If you allow the solvent(water) to evaporate, the solute(sugar) will remain behind (crystallize).

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