Heat Transfer | Class 7 Science Notes
By ConceptScroll Team · Published on 17 July 2026 · 4 min read
Heat Transfer – this guide gives you a concise, exam-ready overview of Heat Transfer from Class 7 Science, written by ConceptScroll editors and reviewed against the latest NCERT textbook.
7.3 Radiation
Radiation is the transfer of heat through electromagnetic waves without requiring any medium. This means heat can travel through vacuum, unlike conduction and convection which require a material medium. The heat we feel from the Sun and from a fire is transferred by radiation. The section explains that all objects emit radiant heat, and a hot object cools down by radiating heat to its surroundings. The warmth felt sitting near a fireplace is due to radiation. The section also discusses why light-colored clothes are preferred in summer as they reflect most heat, keeping us cool, whereas dark-colored clothes absorb more heat and keep us warm in winter. The section illustrates that in many real-life situations, conduction, convection, and radiation occur simultaneously. For example, when heating water in a pan, heat is conducted from the flame to the pan, convection currents heat the water, and radiation warms the surroundings. The traditional room heater 'bukhari' used in the Himalayas is an example where all three heat transfer processes work together.
📊 Diagram: Figure 7.8 shows a pan on a flame heating water, illustrating conduction from flame to pan, convection in water, and radiation warming the surroundings. An image of a bukhari heater shows its design and use in cold regions.
🔗 Connection: Prepares for the next section on the water cycle by explaining the role of heat from the Sun in natural processes.
Frequently asked questions
1. Choose the correct option in each case. (i) Your father bought a saucepan made of two different materials, A and B, as shown in Fig. 7.14. The materials A and B have the following properties— (a) Both A and B are good conductors of heat (b) Both A and B are poor conductors of heat (c) A is a good conductor and B is a poor conductor of heat (d) A is a poor conductor and B is a good conductor of heat (ii) Pins are stuck to a metal strip with wax and a burning candle is kept below the rod, as shown in Fig. 7.15. Which of the following will happen? (a) All the pins will fall almost at the same time (b) Pins I and II will fall earlier than pins III and IV (c) Pins I and II will fall later than pins III and IV (d) Pins II and III will fall almost at the same time (iii) A smoke detector is a device that detects smoke and sounds an alarm. Suppose you are fitting a smoke detector in your room. The most suitable place for this device will be: (a) Near the floor (b) In the middle of a wall (c) On the ceiling (d) Anywhere in the room
1.(i) (c) A is a good conductor and B is a poor conductor of heat. Explanation: In a saucepan, the base (A) is usually made of a good conductor like metal to allow heat to pass quickly for cooking, while the handle (B) is made of a poor conductor (insulator) to prevent heat transfer and avoid burning the hand.
1.(ii) (b) Pins I and II will fall earlier than pins III and IV. Explanation: Pins closer to the heat source (pins I and II) will experience the melting of wax earlier due to conduction o
2. A shopkeeper serves you cold lassi in a tumbler. By chance, the tumbler had a small leak. You were given another tumbler by the shopkeeper to put the leaky tumbler in it. Will this arrangement help to keep the lassi cold for a longer time? Explain.
Yes, this arrangement will help keep the lassi cold for a longer time. Placing the leaky tumbler inside another tumbler reduces the direct exposure of the lassi to the external environment. The outer tumbler acts as an insulating layer, reducing heat transfer by conduction and convection from the surroundings to the lassi. This slows down the warming of the lassi, keeping it cold longer.
3. State with reason(s) whether the following statements are True [T] or False [F]. (i) Heat transfer takes place in solids through convection. [ ] (ii) Heat transfer through convection takes place by the actual movement of particles. [ ] (iii) Areas with clay materials allow more seepage of water than those with sandy materials. [ ] (iv) The movement of cooler air from land to sea is called land breeze. [ ]
(i) False. Heat transfer in solids mainly occurs through conduction, not convection.
(ii) True. Convection involves the actual movement of particles carrying heat.
(iii) False. Clay has very small pores and allows less seepage of water compared to sandy soil which has larger pores.
(iv) True. Land breeze is the movement of cooler air from land to sea, usually at night.
4. Some ice cubes placed in a dish melt into water after sometime. Where do the ice cubes get heat for this transformation?
The ice cubes get heat from the surrounding environment (air and the dish) which is at a temperature higher than the melting point of ice. Heat energy is transferred to the ice cubes by conduction and convection, causing them to melt into water.
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