Lessons 14–15 · 2 lessons · K. T. Suyarov, Z. B. Sangirova, M. T. Umaraliyeva, S. G‘. Xasanova, M. K. Yuldasheva, D. T. Hasanova. Natural Science, Grade 6 (new edition). Republican Education Centre, 2022
14
Practical: Making artificial rain
Textbook, pp. 33–34
GoalShow how rain forms using a model and weigh the advantages and drawbacks of artificial rain.
Rain forms in nature through the water cycle: the Sun’s heat evaporates water, moist air rises and cools, the vapour condenses into tiny droplets – a cloud – and the droplets grow and fall as precipitation. Artificial rain is people’s attempt to help this process and increase precipitation. Usually tiny particles that help droplets form (for example silver iodide or dry ice) are sprayed into clouds from the ground or an aircraft; this requires clouds and enough moisture – you cannot make rain from a clear sky. Advantages: it may reduce drought and help farming and reservoirs. Drawbacks: expensive equipment, results are not guaranteed, and its effects on weather and living nature are not fully understood.
Worked examples
In the model: hot water in the jar evaporates, the vapour touches the cold saucer above and condenses, and the drops grow and fall. The jar is the sea; the cold air under the saucer is the cloud height.
Separate advantages from drawbacks: “reduces drought” – advantage; “needs expensive equipment” – drawback; “increases rainfall” – advantage; “changes the weather” – something to be careful about.
Class activity
“Rain in a cloud” experiment: fill a clear glass with water and carefully add a layer of shaving foam (or cotton wool) on top as the “cloud”. Drip coloured water (food colouring) onto the foam with a dropper: the cloud holds it until it is saturated, then coloured “rain” starts to fall through. Compare with the hot-water/ice jar experiment (lesson 13). Safety: shaving foam is not food – keep it out of mouths and eyes; wash hands afterwards.