Experts have designed these Class 7 Science Notes Chapter 7 Heat Transfer in Nature Class 7 Notes for effective learning.
Class 7 Science Chapter 7 Heat Transfer in Nature Notes
Class 7 Heat Transfer in Nature Notes
Class 7 Science Chapter 7 Notes – Heat Transfer in Nature Notes Class 7
→ Difference in Climate at Different Places: Climate varies from place to place. Gangtok is cold, while Kerala is warm and humid during winter. This is because Kerala is closer to the equator and has a coastline, both of which make it warmer.
→ The Sun—Our Main Heat Source: The Sun gives us heat and light. The equator receives more sunlight, so areas around it are hotter. All heat and weather changes on Earth are mainly caused by the Sun.
→ Why Cooking Utensils Are Made of Metal: Metals are good conductors of heat, meaning they allow heat to pass through quickly, which is why they are used for cooking.
→ Good vs Poor Conductors of Heat:
- Good conductors: Allow heat to pass through them (e.g., metals like iron, copper, steel).
- Poor conductors (insulators): Do not allow heat to pass through them easily (e.g., wood, plastic, air, clay).
→ Understanding Conduction of Heat: In solids like metals, heat moves from the hotter part to the colder part.
This happens without the particles themselves moving — the heat just passes from one particle to the next. This process is called conduction.
→ Why Wool Keeps Us Warm:
Wool traps air, which is a poor conductor of heat. This trapped air prevents body heat from escaping, which is why woollen clothes keep us warm in winter.
→ Designing Warm Houses in Cold Areas: In cold places like Uttarakhand, houses are built using double wooden walls filled with mud or cow dung, which are poor conductors of heat. These houses remain warm during winters and cool during summers.
→ Why Smoke Rises Upward: Hot air rises because air becomes lighter when heated. As smoke is warmer than the surrounding air, it rises up.
→ Convection in Liquids: When we heat water in a beaker over a flame, the water at the bottom of the beaker gets heated up and becomes hot. It expands, becomes lighter, and rises. The water on the sides of the beaker is comparatively cooler and heavier and comes down to take the place of the rising water. This continues till the entire water gets heated. This process of heat transfer is known as convection.
→ Sea Breeze During Day: During daytime, land heats up faster than water. The warm air above the land rises. This causes cooler air to move from the sea towards the land. This movement of cooler air from the sea to the land is called sea breeze.
→ Land Breeze During Night: At night, land cools faster than the sea. Now, warm air above the sea rises and cooler air from the land moves toward the sea, forming a land breeze.
Radiation: Heat Transfer Without Medium: Unlike conduction or convection, radiation does not need any material medium. Heat from the Sun or a fire reaches us through radiation. Sitting near a fire feels warm due to radiation.
→ Choosing Clothes According to Weather:
Light-coloured clothes absorb less heat and reflect most of it, keeping us cool in summer. Dark-coloured clothes absorb heat, keeping us warm in winter.
→ Heat Transfer in Cooking: When water is heated in a pan:
- Heat moves from flame to pan by conduction,
- Water circulates heat by convection,
- Warmth felt around the pan is due to radiation.
All three methods of heat transfer can be observed to happen together.
→ Water Cycle – Powered by Heat: Heat from the Sun evaporates water from oceans, rivers, and even from plants (transpiration). The vapour rises, cools, condenses into clouds, and precipitates to fall as rain or snow-this entire movement is the water cycle.
→ How Water Seepage Happens: Water doesn’t stay only on the £ surface of the Earth—it seeps % into the soil. This process is called infiltration. Water seeps faster through gravel (with bigger gaps) and slower through clay (which has tiny gaps).
→ Aquifers: The water that seeps into the ground gets stored in aquifers—layers of soil, sand, or rock that hold water. This is the water we get from wells and borewells.
→ Water Conservation-Ice Stupas in Ladakh: In cold places like Ladakh, people, during winter create ice stupas—large coneshaped ice towers that slowly melt in summer and provide water for farming and drinking. It’s a smart way of storing water for dry months.
→ Heat: A form of energy that causes substances to become warmer.
→ Temperature: A measure of how hot or cold an object is. It indicates the amount of heat present in a body.
→ Conduction: The process of heat transfer in solids where heat passes from one particle to another without the movement of particles themselves.
→ Convection: A mode of heat transfer in liquids and gases in which particles actually move from the hotter region to the cooler region, creating a cyclic motion.
→ Radiation: The transfer of heat energy without any medium. It can happen even in vacuum, like heat from the Sun reaching the Earth.
→ Conductor: A material that allows heat to pass through it easily.
Examples: metals like copper, aluminium, and steel.
→ Insulator (Poor Conductor):
A material that does not allow heat to pass through it easily. Examples: wood, plastic, rubber, air.
→ Sea Breeze: The movement of cool air from the sea to the land during the day, caused by uneven heating.
→ Land Breeze: The movement of cool air from land to sea at night, as land cools faster than water.
→ Infiltration: The process by which water seeps through soil and rocks into the ground.
→ Groundwater: Water that is stored beneath the Barth’s surface, in spaces between soil and rock particles.
→ Aquifer: A layer of rock, sand, or gravel that stores and carries groundwater. It can be tapped using wells and borewells.
→ Water Cycle: The continuous movement of water through evaporation, condensation, precipitation, and infiltration, which helps recycle water on Earth.
→ Evaporation: The process in which liquid water changes into water vapour due to heat.
→ Condensation: The process in which water vapour cools down and changes into liquid water, forming clouds.
→ Precipitation: Water falling from clouds in the form of rain, snow, or hail.
→ Ice Stupa: A cone-shaped ice structure built in cold areas like Ladakh to gather snow during winter that melts slowly in summer.
→ Bukhari: A traditional room heater used in Himalayan regions, made of iron and used both for warming rooms and cooking.
→ Equator: An imaginary line around the middle of the Earth. Areas near the equator receive more sunlight and heat.
→ Thermometer: An instrument used to measure temperature.
