Water pollution

• in the environment, many things mix or dissolve in water
• water can be polluted by
  • insoluble substances, such as oil, plastics, tyres, tins, glass, toilet waste
  • soluble substances such as soaps, fertilizers, insecticides, acids and other poisons
  • living germs from toilet waste causing water-borne illnesses such as diarrhoea

• Greet the learners.
• Remind them that in their previous lessons, they learnt about dissolving. Ask learners if they can explain what happens when something dissolves.

Answer:  Dissolving involves two substances – a solute and a solvent. The resulting solution is a mixture of both. The dissolved substance is still present in the solution even though it cannot be seen.

• Remind learners that they have also learnt about soluble and insoluble substances. What is the difference between these two?

Answer:  Soluble substances are those that easily dissolve in a solvent, such as water, and include sugar, salt, alcohol and some dishwashing detergents.

Insoluble substances are substances that do not dissolve in a solvent (e.g. chalk is insoluble in water).

• Tell learners that in this lesson they are going to learn how soluble and insoluble substances can be bad for the environment and pollute our water.
• Water is very important for survival.
• Show VIDEO CLIP 1: Introduction to Water (3:47 min.).

In this video learners will see how important water is for survival and that we need to treasure our water resources.

• Ask learners how they know that the water we drink is clean.

Answer:  We can say that water is clean if it does not contain any pollutants or it must be free of pollutants.

• Ask learners to explain what the word pollutant means.

Answer:  Pollutants are substances or objects that do not naturally belong in the water and that are harmful to us and to the environment.

• Show VIDEO CLIP 2: Water pollution (3:19 min.). 
• In this video, learners will learn about water pollution. Contamination of water by harmful substances, which affects life on earth, is termed as water pollution.
• Can the learners think of things that do not belong in the water and that can harm or pollute the water?
• Present an overview of mixtures and water and the three main causes of water pollution by using PRESENTATION 1: Water pollution.

• Learners complete the word search activity in WORKSHEET A: Water pollution word search.
• Guide learners as they undertake this activity and explain how this worksheet will be assessed.
• Teacher to use WORKSHEET A: Memorandum to mark the learners’ work.

• Remind learners that they learnt about ecosystems in term 1.
• Ask learners to explain what an ecosystem is:

Answer: an ecosystem is an area where living and non-living things depend on each other in many ways

• Ask learners to give examples of living and non-living things in an ecosystem:

Answers can include

• Ask learners to give examples of different ecosystems.

Answers can include: rivers, mountains, seas, rocky shores, ponds, wetlands, grasslands, forests and deserts.

• Write the names of these ecosystems on the blackboard and underline all the ecosystems that are heavily dependent on water.
• Remind learners of how important water is in our environment
• Ask learners to identify substances that can pollute our water ecosystems and water resources
  1. Insoluble substances
  2. Soluble substances
  3. Living germs from toilet waste

• Before introducing this activity, the teacher must identify different parts of the school ground that learners can go to do a scientific investigation.
• The purpose of this investigation is to allow learners to identify the different components of a healthy ecosystem as well as substances that can get into our water system and cause harmful pollution.
• Divide learners into small groups of 4 – 5.
• Explain to learners that each group will go investigate a particular part of the school grounds.
• Once they are there, they need to identify:
  • Living and non-living things that make up a healthy ecosystem.
  • Substances that can get into our water systems and cause pollution.
• Learners should take a notebook with them so that they can write down
  • 4 living things in the school grounds that are part of a healthy ecosystem;
  • 4 non-living things that are part of a healthy ecosystem;
  • Unhealthy substances that pollute our school grounds and can cause pollution to our water systems:
    • 2 soluble substances
    • 2 insoluble substances
    • 1 type of germ (or bacteria)
  • After completing their investigation outside, learners should complete WORKSHEET B: Investigation – causes of water pollution.
  • Guide learners as they undertake this activity and explain how the worksheet will be assessed.
  • Allow each group to make a presentation on the results of their investigations.
  • Decide which recommendations to reduce pollution should be implemented in your school.

• Teacher to use WORKSHEET B: Memorandum to mark the learners’ work.

• Show this video clip as a summary of key aspects of water pollution. VIDEO CLIP 3: Learn about water pollution (3:01 min.).
• Answer any questions that learners may have about water pollution.

• Learners complete the activity in WORKSHEET C: Water pollution.
• Guide learners as they undertake this activity and explain how this worksheet will be assessed.
• Teacher to use WORKSHEET C: Memorandum to mark the learners’ work.