- 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.