At the end of this activity, students should be able to explain the composition and properties of natural water: oxygen content, pH, hardness, content of ionic compounds, explain the toxic properties of heavy metals, give examples of poisoning by heavy-metal ions contained in water, discuss the positive and negative effects of using pesticides, explain the eutrophication of water by excess phosphate and describe the purification of tap water and the treatment of sewage.

Originally released by Learnetic, 2016.