Heat Transfer in Nature

About this chapter

Heat Transfer in Nature is Chapter 7 of Class 7 Curiosity. Through Pema and her brother Palden in Gangtok, sitting around a winter fireplace and watching their grandmother cook thukpa in a metal pan, students meet the three modes by which heat travels from one place to another. The chapter builds these core ideas: conduction — Activity 7.1 in which pins stuck with wax fall in order from the candle-end of a metal strip as heat passes particle by particle, with metals as good conductors and wood, glass, clay and porcelain as poor conductors (insulators); why woollen clothes, two thin blankets, hollow bricks and Mori (Uttarkashi) houses with dung-mud between wooden layers keep us warm; convection — Activity 7.2 with the rising paper cup over a candle, Activity 7.3 with the potassium permanganate streak in a beaker, the inflated balloon in the Sun and the rising agarbatti smoke; Activity 7.4 with soil heating faster than water, producing sea breeze by day and land breeze by night in coastal Kerala; radiation — the heat of the fire and the Sun reaching us with no medium needed, and why light clothes are comfortable in summer while dark clothes are comfortable in winter; the saucepan example combining all three modes; the bukhari room-heater of the upper Himalayas as another all-three-modes device; and the water cycle — Sun-driven evaporation and transpiration, condensation into clouds, precipitation, infiltration through soil and rocks (faster through gravel than sand or clay), storage as groundwater in aquifers, the depletion of groundwater and the ice stupa of Ladakh as a water-conservation answer. CTET Paper 2 Science tests this chapter through conduction-vs-convection-vs-radiation pairings, land/sea breeze direction, smoke-detector placement, lassi-in-second-tumbler insulation reasoning, water-cycle process ordering and Ladakh ice stupa. The four tests — Practice 15, Quiz 15, Hard 15, Mastery 30 — cover these ideas at exam depth.