Heat Transfer in Nature
1. Conduction of Heat
- Definition: Heat transfers from hotter to colder parts of an object without particle movement.
- Good Conductors: Metals (e.g., steel, aluminum) allow heat to pass easily; used in cooking utensils.
- Poor Conductors (Insulators): Wood, glass, clay, air; used in cups to keep drinks hot.
- Example: Heat travels through a metal strip, melting wax and causing pins to fall.
2. Convection
- Definition: Heat transfers in liquids and gases by the actual movement of particles.
Examples:
- Hot air rises, cooler air sinks (e.g., rising smoke, heated water in a beaker).
Land and Sea Breeze:
- Day (Sea Breeze): Land heats faster, warm air rises, cooler sea air moves in.
- Night (Land Breeze): Land cools faster, warm sea air rises, cooler land air moves in.
3. Radiation
- Definition: Heat travels directly from a hot object without needing a medium.
- Examples: Sun’s heat reaches Earth; warmth from a fire.
- Key Point: Light-colored clothes reflect heat (cool in summer); dark clothes absorb heat (warm in winter).
4. Water Cycle
- Definition: Continuous movement of water through evaporation, condensation, precipitation, and infiltration.
Stages:
- Evaporation: Water turns into vapor due to Sun’s heat.
- Transpiration: Water evaporates from plants.
- Condensation: Vapor forms clouds.
- Precipitation: Rain, snow, or hail falls.
- Infiltration: Water seeps into the ground, stored as groundwater in aquifers.
- Importance: Replenishes water in rivers, lakes, and oceans; conserves Earth’s water.
5. Groundwater and Aquifers
- Groundwater: Water stored in underground sediments and rocks.
- Aquifers: Layers of sediments/rocks that hold water.
- Issue: Overuse and less infiltration deplete groundwater.
- Solution: Rainwater harvesting and recharge pits replenish groundwater.
6. Applications
- Cooking: Metal utensils for fast heat conduction.
- Clothing: Wool traps air to keep warm; light colors for summer.
- Houses: Hollow bricks trap air to regulate temperature.
- Water Conservation: Ice stupas in Ladakh store water for spring use.
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