NCERT Solutions for Class 7 Science (Curiosity) Chapter 7: Heat Transfer in Nature (NCERT 2026–27)

These Class 7 Science Curiosity Chapter 7 solutions cover Heat Transfer in Nature from the new NCF-2023 textbook (session 2026–27). The chapter explains the three ways heat moves — conduction, convection and radiation — and connects them to everyday nature: land and sea breezes, the water cycle, infiltration of rainwater and groundwater. Every question of the end-of-chapter exercise “Let Us Enhance Our Learning” is reproduced verbatim and solved step by step below.

Class: 7 Subject: Science Book: Curiosity Chapter: 7 Topic: Heat Transfer in Nature Session: 2026–27
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Class 7 Science Curiosity Chapter 7 Solutions – Overview

Chapter 7 of Curiosity, Heat Transfer in Nature, begins with Pema and Palden wondering why some places are hot and others cold. Through simple activities the chapter builds up the three modes of heat transfer. Conduction is heat moving from the hotter part of an object to its colder part without the particles changing position (a metal strip dropping pinned wax). Convection is heat carried by the actual movement of particles in liquids and gases (hot air rising under a paper cup, a coloured streak circulating in heated water). Radiation is heat travelling without any medium — the warmth of a fire or the Sun. These ideas explain land and sea breezes, the use of good and poor conductors in cooking utensils and clothing, the water cycle, the infiltration of rainwater, and groundwater stored in aquifers.

Key Concepts & Definitions

Conduction: the process of heat transfer from the hotter part of an object to its colder part. The heated particle passes heat to its neighbour and so on, but the particles do not move from their positions. It is the main way heat moves in solids.

Good conductors: materials such as metals that allow heat to pass through them easily — used for cooking utensils.

Poor conductors (insulators): materials such as wood, glass, clay, porcelain and air that do not allow heat to pass through easily — used to keep things warm or cool.

Convection: heat transfer by the actual movement of particles. When a liquid or gas is heated it expands, becomes lighter and rises, while cooler, heavier fluid sinks to take its place, setting up a cycle. It is the main way heat moves in liquids and gases.

Radiation: heat transfer that does not need any medium; heat travels directly from a hot object, e.g. the Sun or a fire, to us.

Sea breeze / land breeze: land heats and cools faster than water. By day, warm air over the land rises and cooler air moves from sea to land (sea breeze); by night the reverse happens (land breeze).

Water cycle: the continuous movement of water — upward as water vapour (evaporation, transpiration) and downward as precipitation — through soil, rocks and plants, finally returning to water bodies.

Infiltration: the process of surface water seeping through soil and rocks; water moves more readily where spaces are wide, open and connected.

Aquifer: the underground layer of sediments and rocks that stores water (groundwater) in its pore spaces.

“Let Us Enhance Our Learning” – NCERT Solutions

All questions below are reproduced verbatim from the NCERT Curiosity textbook (Reprint 2026–27); the answers are original and exam-ready.

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

ANSWER (c) A is a good conductor and B is a poor conductor of heat. In a saucepan the body (A) that touches the flame and the food must let heat pass into the food quickly, so it is made of a good conductor (a metal). The handle (B) is held in the hand, so it is made of a poor conductor to stop heat reaching the hand and burning it.

(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

ANSWER (b) Pins I and II will fall earlier than pins III and IV. Heat travels along the strip by conduction from the heated end. Pins I and II are nearer the candle flame, so the wax holding them melts first and they fall before pins III and IV, which are farther away.

(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

ANSWER (c) On the ceiling. Smoke is a mixture of hot gases that is warmer and lighter than the surrounding air, so it rises up by convection and collects near the ceiling first. A detector on the ceiling therefore senses the smoke earliest.

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.

ANSWER Yes, this arrangement helps keep the lassi cold for longer. When one tumbler is placed inside the other, a thin layer of air gets trapped between the two tumblers. Air is a poor conductor of heat, so it slows down the flow of heat from the warm surroundings into the cold lassi. With less heat reaching the lassi, it stays cold for a longer time.

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. [ ]

ANSWER (i) False [F]. In solids the particles cannot move from their fixed positions, so heat is transferred mainly through conduction, not convection. (ii) True [T]. In convection the heated particles of a liquid or gas physically rise while cooler particles sink, so heat is carried by the actual movement of particles. (iii) False [F]. The spaces between clay particles are very narrow, so clay allows the slowest seepage. Sand has wider spaces and allows more seepage than clay. (iv) True [T]. At night the land cools faster than the sea; cooler air then moves from the land towards the sea, and this movement is called the land breeze.

4. Some ice cubes placed in a dish melt into water after sometime. Where do the ice cubes get heat for this transformation?

ANSWER The ice cubes get the heat needed to melt from their surroundings — the warmer air in the room and the dish in contact with the ice. Because the surroundings are warmer than the ice, heat flows from the air to the ice by radiation and from the dish to the ice by conduction. This heat raises the temperature of the ice and changes it from solid to liquid water.

5. A burning incense stick is fixed, pointing downwards. In which direction would the smoke from the incense stick move? Show the movement of smoke with a diagram.

ANSWER The smoke will move upwards, even though the incense stick points downward. Smoke is a mixture of hot gases that is warmer and lighter than the surrounding air, so by convection it always rises up regardless of the direction in which the stick is pointing. Diagram (description): draw the incense stick fixed with its burning tip pointing down. From the tip, the smoke first spreads a little and then curves and rises upward in wavy lines (shown by arrows pointing up), because hot, light smoke goes up while cooler air sinks to take its place.

6. Two test tubes with water are heated by a candle flame as shown in Fig. 7.16. Which thermometers (Fig. 7.16a or Fig. 7.16b) will record a higher temperature? Explain.

ANSWER The thermometer in Fig. 7.16(b) — where the flame heats the test tube near the bottom and the thermometer bulb is higher up in the water — will record the higher temperature. When water is heated at the bottom, it expands, becomes lighter and rises, while cooler water comes down from the top to be heated in turn. By this convection cycle the warm water keeps moving upward and the whole water column gets heated. So heating the lower part warms the water above it effectively. In Fig. 7.16(a), where the heat is applied at the top, the warm water simply stays at the top and the cooler water below is not carried up to be heated, so less heating occurs.

7. Why are hollow bricks used to construct the outer walls of houses in hot regions?

ANSWER Hollow bricks have empty spaces inside them that get filled with air. Air is a poor conductor of heat, so the trapped air slows down the flow of heat through the wall. In hot regions this prevents the outside heat from passing into the house, keeping the inside cool. (The same trapped air also keeps such houses warm in winter by reducing heat loss.)

8. Explain how large water bodies prevent extreme temperature in areas around them.

ANSWER Water heats up and cools down much more slowly than land. During the day and in summer, a large water body absorbs a lot of heat without becoming very hot, so the nearby air does not become extremely warm. During the night and in winter, the water releases this stored heat slowly, so the nearby air does not become extremely cold. Because water moderates the temperature in both directions, places near large water bodies (such as coastal areas) have a milder, more even climate and avoid the extremes of heat and cold experienced inland. This is also why Kerala, with its long coastline, is warmer and more humid than Sikkim.

9. Explain how water seeps through the surface of the Earth and gets stored as groundwater.

ANSWER Rainwater that falls on the ground does not all flow away; some of it sinks downward through the soil and rocks. This process of surface water seeping through soil and rocks is called infiltration. Water seeps more easily where the spaces between particles are wide, open and connected — it passes fastest through gravel, slower through sand and slowest through clay. As the water moves down, it gets stored in the pore spaces of sediments and in the openings in rocks beneath the surface. These underground layers of sediments and rocks that store water are called aquifers, and the water stored in them is called groundwater. This is the water we draw out by digging wells or drilling bore wells.

10. The water cycle helps in the redistribution and replenishment of water on the Earth. Justify the statement.

ANSWER In the water cycle, the Sun’s heat evaporates water from oceans, rivers and lakes, and plants release water vapour by transpiration. This vapour rises, cools and condenses into clouds, which then bring rain, snow and hail (precipitation) over both land and sea. Because rain falls far from where the water first evaporated, water is carried from the oceans to the land — this is redistribution. The rain refills rivers, lakes, ponds and oceans, and the water that infiltrates the ground recharges aquifers — this is replenishment. The cycle also keeps the total amount of water on the Earth roughly constant, ensuring a continuous, renewable supply.

Exploratory Projects

These are open-ended project tasks; suggested approaches are given below.

Society: Visit a site of water harvesting or a recharge pit. Find out from people how they are constructed and how they work. Prepare a report with illustrations. — Visit a rooftop rainwater-harvesting tank or a recharge pit, note how rainwater is collected, filtered and directed into the ground to recharge groundwater, and draw a labelled diagram in your report.

Activity: Tightly wrap a thin paper strip around a metallic rod. Try to burn the paper with a candle while rotating the rod continuously. Does the paper burn? Explain your observations. — The paper does not burn easily, because the metal rod is a good conductor and quickly carries the heat away from the paper, so the paper does not reach its burning temperature.

Activity: Take a sheet of paper. Draw a spiral on it, cut along the spiral and suspend it above a burning candle. Observe what happens and explain. — The paper spiral rotates. Hot air above the candle rises by convection, and as it moves up past the slanted strips of the spiral it pushes them, making the spiral spin.

Extra Practice Questions

Short Answer Type Questions

Q1. Define conduction of heat.

ANSWERConduction is the process of heat transfer from the hotter part of an object to its colder part, in which each heated particle passes heat to its neighbour while the particles themselves stay in their positions. It is the main way heat moves in solids.

Q2. Why do we prefer two thin blankets over one thick blanket to keep warm?

ANSWERAir gets trapped between the two thin blankets. Since air is a poor conductor of heat, this trapped air reduces the flow of heat from our body to the surroundings, so we feel warmer than under a single thick blanket.

Q3. Why are cooking utensils generally made of metals?

ANSWERMetals are good conductors of heat, so they allow heat from the flame to pass quickly into the food. This makes cooking faster and more even, which is why utensils are usually made of metals.

Q4. Heat from the Sun reaches the Earth even through empty space. Which process makes this possible?

ANSWERIt is possible through radiation. Radiation does not need any material medium, so heat from the Sun travels through the vacuum of space and reaches the Earth.

Q5. Why do clothes dry faster on a sunny day?

ANSWEROn a sunny day the heat from the Sun reaches the wet clothes by radiation and warms the water in them. This makes the water evaporate faster, so the clothes dry more quickly.

Long Answer Type Questions

Q1. Describe an activity to show that heat travels through a metal by conduction.

ANSWERTake a metal strip about 15 cm long and attach four pins to it with wax at nearly equal distances, labelling them I, II, III and IV. Fix the strip to a stand and heat the far end with a candle. After some time the pins begin to fall, starting with pin I (nearest the flame), followed by II, III and IV. This shows that heat travels along the strip from the hot end to the cold end: as the heat reaches each pin, the wax melts and the pin drops. The orderly falling proves that heat is conducted through the solid metal, with each particle passing heat to the next without moving from its place. If a wood or glass strip is used instead, the pins do not fall, because those materials are poor conductors of heat.

Q2. Explain the formation of sea breeze and land breeze with the help of heat transfer.

ANSWERLand heats up faster than water during the day and cools faster than water at night. By day, the land becomes hotter than the sea, so the air above the land gets warm, expands, becomes lighter and rises. Cooler air from over the sea then moves towards the land to take its place; this movement of cool air from sea to land is called the sea breeze, and it relieves coastal people from the heat. At night the process reverses: the land cools faster than the water, so the air above the sea is now warmer and rises, and cooler air from the land moves towards the sea. This movement of air from land to sea is called the land breeze. Thus the wind direction near a seashore reverses between day and night because of the different rates at which land and water heat and cool — an example of convection.

Q3. Explain conduction, convection and radiation using the single example of heating water in a pan over a flame.

ANSWERWhen water is heated in a pan over a flame, all three modes of heat transfer occur together. First, heat passes from the flame into the metal pan by conduction, because the metal is a good conductor and its particles pass heat from the hot base to the rest of the pan without moving. Next, the water at the bottom of the pan gets heated, expands, becomes lighter and rises, while cooler, heavier water from the top sinks to take its place; this cycle of moving water spreads the heat through the whole pan by convection. Finally, the warmth that we feel in the air around the flame and the hot pan, without touching them, reaches us by radiation, which needs no medium. So a single everyday act of heating water neatly demonstrates conduction in the pan, convection in the water and radiation to the surroundings.

MCQs & Assertion–Reason

1. The transfer of heat from the hotter part of a solid to its colder part is called:

(a) convection    (b) radiation    (c) conduction    (d) evaporation

2. Which of the following is the best conductor of heat?

(a) wood    (b) aluminium    (c) glass    (d) clay

3. In liquids and gases, heat is transferred mainly by:

(a) conduction    (b) convection    (c) radiation    (d) infiltration

4. The mode of heat transfer that does not require any medium is:

(a) conduction    (b) convection    (c) radiation    (d) condensation

5. During the day, the movement of cooler air from the sea towards the land is called:

(a) land breeze    (b) sea breeze    (c) monsoon    (d) cyclone

6. Woollen clothes keep us warm in winter because:

(a) wool produces heat    (b) wool traps air, a poor conductor    (c) wool is a good conductor    (d) wool radiates heat to us

7. Water seeps fastest through:

(a) clay    (b) sand    (c) gravel    (d) all equally

8. The underground layer of sediments and rocks that stores water in its pore spaces is called:

(a) aquifer    (b) glacier    (c) reservoir    (d) infiltration

9. The process of surface water seeping through soil and rocks is called:

(a) evaporation    (b) condensation    (c) infiltration    (d) precipitation

10. Smoke from a fire rises up because hot smoke is:

(a) heavier than air    (b) lighter than the surrounding air    (c) a good conductor    (d) solid

Answer key: 1-(c), 2-(b), 3-(b), 4-(c), 5-(b), 6-(b), 7-(c), 8-(a), 9-(c), 10-(b).

For each Assertion–Reason question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.

A-R 1. Assertion: We prefer clay or porcelain cups for hot tea and coffee.

Reason: Clay and porcelain are poor conductors of heat, so the drink stays hot longer.

A-R 2. Assertion: Heat from the Sun reaches the Earth by radiation.

Reason: Radiation does not require any material medium for heat transfer.

A-R 3. Assertion: In conduction, the particles of the solid move from the hot end to the cold end carrying heat.

Reason: In conduction, each heated particle passes heat to its neighbour without leaving its own position.

A-R 4. Assertion: A sea breeze blows from the sea towards the land during the day.

Reason: During the day the land heats faster than the sea, so warm air over the land rises and cooler sea air moves in.

A-R 5. Assertion: Hollow bricks help keep houses cool in summer and warm in winter.

Reason: The air trapped inside hollow bricks is a good conductor of heat.

Answer key: 1-(A), 2-(A), 3-(D), 4-(A), 5-(C).

Quick Revision Summary

  • Heat is transferred in three ways: conduction, convection and radiation.
  • Conduction — heat moves from the hotter to the colder part of an object; particles do not move; main mode in solids.
  • Good conductors (metals) let heat pass easily; poor conductors / insulators (wood, glass, clay, air) do not.
  • Convection — heat carried by the actual movement of particles; main mode in liquids and gases; explains land and sea breezes.
  • Radiation — heat transfer needing no medium; brings the Sun’s and a fire’s heat to us.
  • Land heats and cools faster than water, giving milder climates near large water bodies.
  • Water cycle redistributes and replenishes water; infiltration stores it as groundwater in aquifers.

Common Mistakes to Avoid

Watch out for these

  • Saying particles move in conduction — in conduction the particles stay in place; they move only in convection.
  • Calling air a good conductor — trapped air is actually a poor conductor, which is why it insulates blankets, woollens and hollow bricks.
  • Mixing up land and sea breeze — sea breeze blows from sea to land (day); land breeze from land to sea (night).
  • Thinking radiation needs a medium — only conduction and convection need a medium; radiation does not.
  • Writing that clay allows the most seepage — gravel allows the fastest, clay the slowest.
  • Confusing infiltration with evaporation — infiltration is water seeping down into the ground, not rising as vapour.

How to score full marks in this chapter

Always name the mode of heat transfer and give its reason in your answer — e.g. “by convection, because hot air rises and cool air sinks.” Remember the rule: solids → conduction, liquids & gases → convection, no medium → radiation. Use the textbook’s own examples (the pin-and-wax strip, the paper-cup activity, the coloured streak in water, hollow bricks, two thin blankets) to support your explanations, and learn the breeze diagrams and the water-cycle terms (evaporation, transpiration, condensation, precipitation, infiltration, aquifer).

Frequently Asked Questions

What is Class 7 Science Curiosity Chapter 7 about?

Chapter 7, Heat Transfer in Nature, explains the three ways heat moves — conduction, convection and radiation — and links them to good and poor conductors, land and sea breezes, the water cycle, infiltration of rainwater and groundwater stored in aquifers.

What is the difference between conduction, convection and radiation?

In conduction, heat passes from particle to particle without the particles moving (mainly in solids). In convection, heat is carried by the actual movement of heated particles (mainly in liquids and gases). In radiation, heat travels directly without any medium, as from the Sun or a fire.

Why does the smoke of an incense stick always rise up?

Smoke is a mixture of hot gases that is warmer and lighter than the surrounding air, so by convection it always rises upward — even if the burning incense stick is pointed downwards.

Are these Class 7 Science Curiosity Chapter 7 solutions free?

Yes. All solutions are free and follow the official NCERT Curiosity textbook for session 2026–27.

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