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Why does a steel spoon in hot tea get hot at the handle? Why does smoke go up? Why do two thin blankets feel warmer than one thick one? Chapter 7 of the Class 7 science book answers all of these with three words: conduction, convection and radiation. This guide explains each one, gives you a quick test for telling them apart, works through examples and lists the mistakes students most often make.
What does Chapter 7 of Class 7 Curiosity cover?
Heat Transfer in Nature is Chapter 7 of NCERT's *Curiosity* for Grade 7 (first edition April 2025, reprint 2026-27). It covers:
Conduction in a metal strip, and good and poor conductors of heat.
Air as an insulator: woollen clothes, layers, hollow bricks and Himalayan houses.
Convection in air (a paper cup rising over a candle) and in water (a potassium permanganate streak).
Land and sea breezes.
Radiation, light and dark clothes, and the bukhari stove that uses all three.
The water cycle, infiltration, groundwater and aquifers.
How do you tell conduction, convection and radiation apart?
Ask two questions in order.
Is there a material between the hot thing and the cold thing? If not, it must be radiation. Radiation needs no medium, which is why the Sun's heat crosses space.
If there is a material, does that material move? If the particles stay in place and pass heat to their neighbours, it is conduction. If the warm material itself flows from one place to another, it is convection.
In solids, heat moves mainly by conduction. In liquids and gases, it moves mainly by convection. A hot pan cooling on the counter loses heat by radiation too, because the chapter notes that all objects radiate heat.
Worked examples
Example 1: the pins on the metal strip. Four pins are fixed with wax along a metal strip, about 2 cm apart, labelled I to IV from the heated end. Which falls first? Pin I, because heat reaches it first. Then II, III and IV, in order. If the strip were wood, the pins would not fall, because wood is a poor conductor.
Example 2: soil and water in the Sun. The chapter has you measure the temperature of a bowl of soil and a bowl of water every 5 minutes for 20 minutes. Suppose your readings are:
Soil: 28 °C at the start, 36 °C after 20 minutes.
Water: 28 °C at the start, 31 °C after 20 minutes.
The soil rose 36 − 28 = 8 °C and the water 31 − 28 = 3 °C. Soil heats faster, and the chapter shows it also cools faster. (Your numbers will differ; the pattern should not.)
Example 3: the sea breeze. Use Example 2. In the daytime, land warms faster than the sea, so warm air over the land rises and cooler air moves in from the sea. That is a sea breeze. At night the land cools faster, the air over the sea is warmer and rises, and cooler air moves from land to sea: a land breeze. Both are convection.
Example 4: heating water in a pan. Heat reaches the pan from the flame by conduction, the water heats up by convection, and the warmth you feel standing nearby is radiation. One situation, all three processes.
What mistakes do students make about heat?
Ideas about heat start long before school. In interviews with 37 middle school students, Lewis and Linn (1994) found many believed that metals "conduct", "absorb", "trap" or "hold" cold better than other materials, and that aluminium foil would keep a cold drink cold better than wool. Adults held similar intuitive ideas. Teaching that built on students' own intuitions led to clear improvements.
Watch for these in your own answers:
"Heat rises." It is hot air or hot water that rises, because it expands and becomes lighter for its size than the cooler fluid around it. Heat itself can travel down a spoon or sideways from a fire.
"A woollen sweater makes heat." Wool traps air, and air is a poor conductor, so it slows the heat leaving your body. Two thin blankets trap a layer of air between them, which is why they can feel warmer than one thick one.
"A steel bench feels colder, so it is colder." On a cool morning a steel bench and a wooden one in the same place are at about the same temperature. Steel feels colder because it conducts heat away from your hand faster.
"Radiation needs air." It needs nothing; that is the whole point.
"Convection happens in solids." It needs particles that can move, so it happens in liquids and gases.
How does heat connect to the water cycle in this chapter?
The second half of the chapter uses the Sun's heat to explain evaporation, condensation, precipitation and infiltration. The worked fact to remember is the seepage activity: water passes fastest through gravel, slower through sand and slowest through clay, because gravel has the widest spaces between particles. Water stored in those spaces underground is groundwater, and the layers that hold it are aquifers.
A one-week practice routine
Day 1: Make a list of ten everyday examples (tea cup, kite rising, sunbathing, ironing) and label each with the two-question test.
Day 2: Redo Example 2 with your own numbers, or with real readings if you can do the activity with an adult.
Day 3: Draw the sea breeze and land breeze diagrams from memory, with arrows.
Day 4: Answer the chapter questions without the book, then check. Pay attention to the smoke detector question; think about which way warm smoke moves.
Day 5: Explain to a parent why clay cups keep tea hot longer than steel ones.
For temperature itself, our Class 6 guide to temperature and its measurement is a useful refresher. If a process is hard to picture, the Fermi Simulation Lab has interactive simulations for ideas that are easier to see than read.
Before your next class, label five things in your kitchen as conduction, convection or radiation.
