Heat Transfer in Nature Chapter Summary with NCERT Solution Class 7 Chapter 7 2025

✅ Heat Transfer in Nature – Chapter Summary with NCERT Solution PDF

Heat Transfer in Nature (AI Image)

Heat is an important form of energy. It affects our daily lives, weather, climate, and even the water cycle. But have you ever wondered how heat moves from one place to another? The Sun heats the Earth, a stove heats a pan, warm air rises, hot utensils cool down – all these happen due to heat transfer. In nature, heat is transferred in three major ways: conduction, convection, and radiation.

✅ 1. Conduction – Heat Transfer in Solids

Conduction is the process by which heat moves through solids.

When you heat one end of a metal rod, after a while, the entire rod becomes hot. Why? Because in conduction, heat travels from the hotter part to the colder part.

✅ Important points:

• In solids, particles do not move from their place, but they pass heat from one particle to another.
• Metals allow heat to pass easily, so they are good conductors.
• Wood, plastic, glass, clay, and rubber do not allow heat to pass easily, so they are poor conductors or insulators.

This is why:

• Cooking utensils are made of metals – they heat fast.
• Handles of utensils are made of plastic or wood – they do not get hot.
• Clay and porcelain cups keep tea hot for a long time.
• Woollen clothes trap air, and air is a poor conductor, so they keep us warm.
• Two thin blankets are warmer than one thick blanket because air trapped between them reduces heat loss.

Even houses in cold places use wood, mud, and hollow bricks to stop heat loss, because poor conductors keep houses warm.

✅ 2. Convection – Heat Transfer in Liquids and Gases

Convection happens when heat moves by the actual movement of particles in liquids and gases.

When air or water is heated, it expands and becomes lighter. The lighter hot air or water rises up, and cooler, heavier air or water replaces it. This continuous movement creates a convection current.

✅ Real-life examples:

• Smoke rising from fire – because hot air rises.
• Hot air balloons fly using this principle.
• When water is heated in a pan, the bottom becomes hot first and rises upward.

⭐ Sea Breeze and Land Breeze

• Daytime: Land heats faster than the sea. Hot air over land rises, and cool air from the sea comes in. This is Sea Breeze.
• Night time: Land cools faster than the sea. Cool air from land moves towards the sea. This is Land Breeze.

This is why coastal areas have pleasant weather.

✅ 3. Radiation – Heat Without a Medium

Radiation is heat transfer without any medium.

Heat from the Sun travels through space and reaches Earth through radiation. Even if there is no air or solid object in between, heat can still travel in this method.

Examples:

• You feel warm when you sit near a fire.
• A hot pan cools down by radiating heat.
• Light-colored clothes reflect heat, so we wear them in summer.
• Dark-colored clothes absorb heat, so they keep us warm in winter.

So, radiation helps us feel warmth directly from a hot object.

✅ Heat in Daily Life

• Most activities around us involve all three forms of heat transfer:
• A metal pan on the stove: heat moves to the pan by conduction
• Water inside heats up by convection
• Warmth felt near the stove is due to radiation

✅ Role of Heat in the Water Cycle

Sunlight heats water in oceans, rivers, and lakes. Water evaporates and rises as water vapor. Plants also release water vapor through transpiration. As the vapor rises higher, it cools and forms clouds. Clouds bring rain, snow, or hail, called precipitation.

This continuous movement of water from the Earth to the atmosphere and back is called the Water Cycle.

It helps maintain water in rivers, lakes, and oceans and also refills groundwater.

✅ Groundwater and Infiltration

When rainwater falls, some of it seeps underground through soil and rocks. This process is called infiltration. Water stores in underground layers known as aquifers. We use this water by digging wells and borewells.

Due to increasing population and cemented surfaces, less water goes underground, causing groundwater depletion.

Rainwater harvesting and recharge pits help increase groundwater levels.

✅ Conclusion

• Heat transfer is an important natural process.
• Conduction works in solids.
• Convection works in liquids and gases.
• Radiation needs no medium and brings heat from the Sun.

These processes help us cook food, stay warm, build houses, and most importantly, drive the water cycle, which makes life on Earth possible.

~~The END~~

Chapter 7 Heat Transfer in Nature

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