Purification and Quality of Water Project

Aim

To investigate the quality and purity of different water samples and explore simple methods used to purify water.

Learning Outcome

• Test water samples for impurities.
• Measure the pH of water samples.
• Identify contaminants in water.
• Compare different water samples.
• Investigate simple filtration systems.
• Explain how water can be purified.
• Understand why clean water is important for human health and the environment.

Time Allocation

Approximately 60 to 90 minutes depending on the number of investigations completed.

This practical can also be expanded into a formal classroom project over several lessons.

How Does It Work?

Water in nature may contain dissolved substances, dirt, sand, mud, microorganisms and chemical contaminants.

Some impurities can be seen, while others are dissolved in the water and cannot easily be observed.

As dirty water passes through layers of a filter, larger particles become trapped first, smaller particles are trapped in lower layers, and the water becomes cleaner.

Activated charcoal can remove some dissolved impurities through adsorption, where substances stick to the surface of the charcoal.

Scientific Background

The hydrosphere includes all water found on Earth, including rivers, dams, oceans, groundwater, ice and water vapour.

As water moves through the environment, it can dissolve substances from rocks, soil, plants, animals and pollution sources.

Water quality can be affected by:

• pH
• dissolved salts
• carbonates
• chlorides
• nitrates
• nitrites
• suspended solids
• microorganisms

Filtration removes suspended solid particles but does not necessarily remove dissolved chemicals or microorganisms.

Different water purification systems are used around the world to make water safe for human use.

Hypothesis

If different water samples are tested and filtered, then they will show different levels of purity and contamination because water sources contain different impurities.

Variables

Independent Variable

Type of water sample tested.

Dependent Variables

• pH value.
• Presence of contaminants.
• Water clarity before and after filtration.
• Presence of solid particles.
• Presence of dissolved substances.

Control Variables

• Same testing methods.
• Same amount of water used.
• Same filter materials.
• Same chemical test solutions.
• Same observation conditions.

Water Sample Options

Teachers may use:

• Tap water
• Rainwater
• River water
• Dam water
• Borehole water
• Muddy water
• Bottled water
• Pond water

Experiment 1: Test for Foreign Matter

Aim

To determine whether water samples contain visible solid impurities.

Apparatus

• Filter paper
• Funnel
• Conical flask
• Different water samples
• Beakers

Safety Precautions

• Do not drink any water sample.
• Wash hands after handling environmental water.
• Clean up spills immediately.

Method

1. Fold a piece of filter paper and place it inside a funnel.
2. Place the funnel into a conical flask.
3. Pour a small amount of the first water sample through the filter paper.
4. Observe the filter paper carefully.
5. Record whether any solid particles remain on the filter paper.
6. Repeat the process for all water samples.

Results Table

Water Sample	Appearance Before Filtration	Residue on Filter Paper	Appearance After Filtration
Sample 1
Sample 2
Sample 3

What Learners Should Observe

• Suspended particles trapped on the filter paper.
• Cleaner water after filtration.
• Differences between water samples.

Conclusion

Filtration removes visible solid particles from water but may not remove dissolved substances or microorganisms.

Experiment 2: Testing pH and Water Quality

Aim

To compare the pH and quality of different water samples.

Apparatus

• Universal indicator paper
• Different water samples
• Pipettes
• Test tubes

Safety Precautions

• Avoid contact with contaminated water samples.
• Handle test strips carefully.
• Wash hands after the investigation.

Method

1. Dip a strip of universal indicator paper into the first water sample.
2. Remove the strip and compare the colour to the pH chart.
3. Record the pH value.
4. Observe and record any colour differences.
5. Repeat for all water samples.

Results Table

Water Sample	pH Value	Observation
Tap water
River water
Rainwater
Distilled water

What Learners Should Observe

• Different water samples may have different pH values.
• Some water samples may be more acidic or alkaline than others.

Conclusion

Different water sources may contain different dissolved substances that affect the pH of the water.

Experiment 3: Test for Chlorides and Carbonates

Aim

To test water samples for the presence of chlorides and carbonates.

Apparatus

• Test tubes
• Pipettes
• Water samples

Chemicals

• 0.1 M silver nitrate solution
• 0.1 M barium nitrate solution
• 0.1 M nitric acid

Safety Precautions

Method

Testing for Carbonates

1. Add a few drops of barium nitrate solution to the water sample.
2. Observe whether a precipitate forms.
3. Add a few drops of nitric acid.
4. Record all observations.

Testing for Chlorides

1. Add a few drops of silver nitrate solution to a fresh sample.
2. Observe whether a precipitate forms.
3. Add a few drops of nitric acid.
4. Record all observations.

Results Table

Water Sample	Carbonate Test Result	Chloride Test Result
Sample 1
Sample 2
Sample 3

What Learners Should Observe

• Precipitates forming in some water samples.
• Differences in contamination levels between samples.

Conclusion

Some water samples may contain dissolved chlorides or carbonates depending on their source.

Experiment 4: Brown Ring Test for Nitrates

Aim

To test water samples for nitrate contamination.

Apparatus

• Test tubes
• Pipettes
• Water samples

Chemicals

• Iron(II) sulphate solution, FeSO₄
• Dilute sulphuric acid
• Concentrated sulphuric acid

Safety Precautions

Method

1. Fill a test tube one-quarter full with the first water sample.
2. Test the pH using universal indicator paper.
3. Add a few drops of dilute sulphuric acid to make the solution slightly acidic.
4. Add an equal amount of iron(II) sulphate solution.
5. Carefully add two to three drops of concentrated sulphuric acid down the side of the test tube.
6. Observe the reaction carefully.
7. Repeat for all water samples.

Results Table

Water Sample	Observation	Presence of Nitrates
Sample 1
Sample 2
Sample 3

What Learners Should Observe

• Formation of a brown ring in contaminated samples.
• Differences between water samples.

Conclusion

Some water samples may contain nitrates from environmental contamination such as fertilisers or pollution.

Experiment 5: Simple Water Filtration System

Aim

To build and investigate a simple water filtration system.

Apparatus

• Plastic bottle with bottom removed
• Cotton wool or cotton balls
• Fine sand
• Gravel
• Small stones or pebbles
• Activated charcoal, optional
• Elastic band
• Cloth or filter material
• Dirty water
• Collection jar or beaker

Safety Precautions

• Do not drink the filtered water.
• Treat all dirty water as contaminated.
• Wash hands after handling dirty water.
• Clean up spills immediately.

Method

1. Stretch a piece of cloth over the narrow end of the bottle and secure it with an elastic band.
2. Turn the bottle upside down.
3. Place cotton wool into the bottom section of the bottle.
4. Add a layer of fine sand.
5. Add a layer of activated charcoal if available.
6. Add a layer of gravel.
7. Add a layer of larger stones or pebbles.
8. Place the bottle over a clean collection container.
9. Slowly pour dirty water into the filter.
10. Observe the filtered water.
11. Compare the water before and after filtration.
12. Repeat the filtration if required.

Results Table

Observation	Before Filtration	After Filtration
Water colour
Visible particles
Clarity

What Learners Should Observe

• Larger particles trapped by stones and gravel.
• Smaller particles trapped by sand and cotton wool.
• Cleaner water after filtration.
• Repeated filtration improving water clarity.

Expected Results

The water should appear cleaner after filtration, although it may still contain dissolved substances or microorganisms.

Conclusion

Layered filtration systems can remove many visible impurities from water. Different filter layers trap different sizes of particles.

Although filtered water may appear cleaner, it may still require boiling or chemical treatment before it is safe to drink.

Questions for Learners

1. Which water sample appeared cleanest?
2. Which water sample contained the most visible impurities?
3. What was the pH of each sample?
4. What is the purpose of filtration?
5. Why is charcoal useful in water filters?
6. Why should filtered water still be boiled before drinking?
7. What contaminants may still remain after filtration?
8. Which experiment provided the clearest evidence of contamination?
9. Why is clean water important for human health?
10. Why should polluted water not be released into rivers and dams?

Common Mistakes

• Not labelling water samples clearly.
• Using contaminated apparatus.
• Using too much reagent during chemical tests.
• Pouring water too quickly through the filter.
• Assuming clear water is always safe to drink.
• Forgetting to record observations carefully.

Teacher Notes

• This investigation works well as a formal project because learners can collect local water samples.
• Distilled water should be used as a control sample.
• Keep the filtration activity simple and practical.
• The brown ring test should only be done under strict supervision.
• Reinforce that filtration does not remove all dissolved substances or microorganisms.
• Encourage learners to compare environmental water samples with treated tap water.

Teacher Tip

Extension Activity

Ask learners to design improved filtration systems, compare repeated filtration results, investigate activated charcoal, or compare filtration with boiling and chlorination methods.

Real-World Application

Water purification and testing are important in drinking water treatment, environmental monitoring, wastewater treatment, farming, mining, industry and public health.

Clean water is essential for healthy ecosystems and safe human living conditions.