On a cold Gangtok evening, Pema wonders: why are cooking pots made of metal, but tea cups made of clay?
Key idea
Conduction
Heat passes from the hotter part of an object to its colder part, particle by particle, without the particles themselves moving.
Good conductors
Metals let heat pass through easily — that's why cooking utensils are metal.
Poor conductors (insulators)
Wood, glass, and clay resist heat flow — that's why tea stays hot longer in a clay cup.
Key idea
Convection
When air or liquid is heated, it expands, becomes lighter, and rises — cooler fluid moves in to take its place, creating a current.
In one lineConvection is heat transfer through the actual movement of particles in a liquid or gas — the main way heat moves in liquids and gases.
Key idea
Land Breeze and Sea Breeze
1
Daytime: sea breeze
Land heats faster than water. Warm air rises over the hot land, and cool air moves in from the sea.
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2
Night: land breeze
Land cools faster than water. Warm air now rises over the (relatively warmer) sea, and cool air moves from land toward it.
Key idea
Radiation
Heat transfers directly from a hot objectlike fire or the Sun — to us, without needing any medium at all.
Clothing and colourLight-coloured clothes reflect heat (comfortable in summer); dark-coloured clothes absorb heat (comfortable in winter).
Key idea
Conduction, Convection, and Radiation Together
1
Conduction
Heat travels from the flame into the metal pan.
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2
Convection
Heat circulates through the water inside the pan.
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3
Radiation
You feel warmth in the air near the flame, directly.
Key idea
The Water Cycle
Evaporation & transpiration
Water vapour rises, cools
Condensation into clouds
Precipitation: rain, snow, hail
Key idea
How Fast Does Water Seep?
Material | Seepage speed | Why
Gravel
Fastest — Widest spaces between particles
Sand
Medium — Smaller spaces than gravel
Clay
Slowest — Tiny, tightly packed spaces
Key idea
Groundwater and Aquifers
1
Groundwater
Water that has seeped down and is stored in the pore spaces of sediments and openings in rocks.
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2
Aquifer
The underground layer of sediment or rock that stores groundwater — wells and borewells draw from it. Rainwater harvesting helps replenish it.
Chapter · Key terms to remember
Key Terms
Conduction
Heat transfer through particles, without them moving.
Convection
Heat transfer by particles of liquid or gas moving.
Radiation
Heat transfer needing no medium at all.
Chapter · Key terms to remember
More Key Terms
Sea breeze / Land breeze
Cool air moving sea→land by day / land→sea by night.
Water cycle
The continuous movement of water, Earth to sky and back.
Infiltration
Surface water seeping through soil and rock.
Chapter · Key terms to remember
More Key Terms
Groundwater
Water stored beneath the surface.
Aquifer
An underground layer that stores groundwater.
Questions for your notebook
Write these down, then discuss
1
Choose the correct option: a saucepan's handle (B) and base (A) — what is true of their materials? Also: which pins fall first on a heated metal strip? And: where's the best spot for a smoke detector?
2
A shopkeeper puts a leaky tumbler of cold lassi inside a second tumbler. Will this keep the lassi cold longer? Explain.
3
True or False, with reasons: (i) Heat transfer in solids happens by convection. (ii) Convection happens by particles actually moving. (iii) Clay lets water seep through faster than sand. (iv) Cool air moving from land to sea is called land breeze.
Project as-is — students copy the questions, then the class discusses answers together.