Activity 4.11

Activity . Take about mL of distilled water (or rain water) and mL of hard water (from a tubewell or hand-pump) in separate test tubes. Add a couple of drops of soap solution to both. Shake the test tubes vigorously for an equal period of time and observe the amount of foam formed. In which test tube do you get more foam? In which test tube do you observe a white curdy precipitate? Note for the teacher : If hard water is not available in your locality, prepare some hard water by dissolving hydrogencarbonates/ sulphates/chlorides of calcium or magnesium in water.