Chapter 7: Heat Transfer in Nature — Class 7 Science
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Summary, key terms, important questions and a practice quiz with AI diagnosis for each.
Chapter 7: Heat Transfer in Nature
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In conduction, how does heat move and what happens to the particles?
Summary
This chapter explains the three ways heat moves from one place to another — conduction, convection, and radiation — and links them to the water cycle and groundwater. In conduction, heat passes from the hotter part of an object to its colder part, with particles passing heat to their neighbours without moving from their positions; this is shown by pins falling off a heated metal strip in order. Materials like metals are good conductors of heat, while wood, glass, clay, and trapped air are poor conductors (insulators) — which is why metal pots are used for cooking but woollen clothes, two thin blankets with air between them, and hollow bricks keep us warm. In convection, heat is carried by the actual movement of particles in liquids and gases: warm air or water expands, becomes lighter, and rises while cooler material sinks, explaining rising smoke, the coloured streak in heated water, and land and sea breezes that arise because land heats and cools faster than water. In radiation, heat travels directly without any medium, as it does from the Sun and a fireplace; dark surfaces absorb more heat and light surfaces reflect it. The chapter then connects heat to the water cycle: the Sun's heat evaporates water from oceans, rivers, and plants (transpiration); the vapour rises, cools, and condenses into clouds, which bring precipitation as rain, snow, or hail; the water returns to water bodies and seeps into the ground. This seeping, called infiltration, is fastest through gravel and slowest through clay; the water stored underground in the pore spaces of sediments and rocks is groundwater, held in layers called aquifers, which must be conserved through rainwater harvesting and recharge.
Conduction of heatConvection and land and sea breezesRadiationThe water cycleInfiltration, groundwater, and aquifers
Key terms
Conduction
The transfer of heat from the hotter part of an object to its colder part, with particles passing heat to their neighbours without moving from their positions.
Convection
The transfer of heat by the actual movement of particles of liquids and gases, as warm material rises and cooler material sinks.
Radiation
The transfer of heat directly from one place to another without needing any medium, as from the Sun or a fire.
Conductor and insulator of heat
A conductor allows heat to pass through easily (like metals); an insulator or poor conductor does not (like wood, air, or clay).
Water cycle
The continuous movement of water — upward as vapour and downward through precipitation — through soil, rocks, plants, and water bodies.
Infiltration
The process of surface water seeping through soil and rocks into the ground.
Aquifer
An underground layer of sediments and rocks that stores water in its pore spaces as groundwater.
Important questions
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Conduction
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The transfer of heat from the hotter part of an object to its colder part, with particles passing heat to their neighbours without moving from their positions.
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Practice quiz · Heat Transfer in Nature
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