NCERT Solutions for Class 7 Science Curiosity Chapter 7: Heat Transfer in Nature by PW

Heat is involved in many everyday situations, but understanding how it moves from one place to another can be confusing. Why does a metal utensil become hot, why does ice melt, how does smoke rise, and why do sea and land breezes occur? Questions about hollow bricks, groundwater and changes in temperature also require an understanding of how heat behaves in different materials and surroundings.

The Class 7 Science Curiosity Chapter 7 NCERT Solutions explain these concepts through questions from Heat Transfer in Nature. They cover conduction, convection, insulation, sea and land breezes, groundwater formation and the water cycle with clear answers and simple explanations.

Class 7 Science Curiosity Chapter 7 NCERT Solutions

The following solutions explain the textbook questions on heat transfer, conduction, convection, insulation and related natural processes.

Q1. Choose the correct option in each case.

(i) Your father bought a saucepan made of two different materials, A and B. The materials A and B have the 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.

The body of the saucepan needs to transfer heat efficiently, so it is made from a good conductor. The handle can be made from a poor conductor or insulating material so that it does not become excessively hot while handling the saucepan.

(ii) Pins are stuck to a metal strip with wax and a burning candle is kept below the rod. Which of the following will happen?

(a) All 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: (d) Pins II and III will fall almost at the same time.

Heat travels through the metal strip by conduction. The pins closest to the heated region receive heat first, causing the wax holding them to melt earlier. Therefore, pins II and III fall almost at the same time.

(iii) A smoke detector is a device that detects smoke and sounds an alarm. Where should it be placed?

(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 and hot gases generally rise because heated air becomes less dense. Placing a smoke detector on the ceiling allows it to detect rising smoke more effectively.

Q2. 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. Will this arrangement help to keep the lassi cold for a longer time?

Answer: Yes.

Air gets trapped between the two tumblers. Since air is a poor conductor of heat, the trapped air reduces the transfer of heat from the surroundings to the cold lassi. As a result, the lassi can remain cold for a longer time.

Q3. State with reason whether the following statements are True or False.

(i) Heat transfer takes place in solids through convection.

Answer: False.

Heat mainly transfers through conduction in solids. Convection involves the movement of particles and occurs mainly in fluids such as liquids and gases.

(ii) Heat transfer through convection takes place by the actual movement of particles.

Answer: True.

During convection, warmer parts of a fluid move while cooler parts move in the opposite direction. This movement transfers heat from one region to another.

(iii) Areas with clay materials allow more seepage of water than those with sandy materials.

Answer: False.

Sandy soil generally has larger spaces between its particles, allowing water to seep through it more easily than through clay soil.

(iv) The movement of cooler air from land to sea is called land breeze.

Answer: True.

At night, land cools faster than the sea. The cooler air over the land moves towards the sea, producing a land breeze.

Q4. Some ice cubes placed in a dish melt into water after some time. Where do the ice cubes get heat for this transformation?

Answer:

The ice cubes get heat from their surroundings.

• The surrounding air is warmer than the ice, so heat transfers from the air to the ice.

• The dish may also be warmer than the ice, allowing heat to transfer from the dish to the ice cubes.

• The ice absorbs this heat and changes from solid ice into liquid water.

Thus, the heat required for melting comes from the warmer surroundings.

Q5. A burning incense stick is fixed, pointing downwards. In which direction would the smoke move?

Answer: The smoke will move upward.

The burning incense produces hot gases and smoke. The heated air becomes less dense and rises upwards. Therefore, the smoke moves upward even when the incense stick is pointing downwards.

Q6. Two test tubes with water are heated by a candle flame as shown in the figure. Which thermometer will record a higher temperature?

Answer: The thermometer in Fig. 7.16(a) will record a higher temperature.

In Fig. 7.16(a), the candle heats the water at the bottom of the test tube. The heated water becomes less dense and rises upwards. Cooler water moves down to take its place, producing convection.

Since the thermometer is placed near the top, the rising hot water reaches it and causes it to record a higher temperature. In Fig. 7.16(b), the position of heating does not allow the hot water to reach the thermometer as effectively.

Q7. Why are hollow bricks used to construct the outer walls of houses in hot regions?

Answer:

Hollow bricks contain air spaces inside them. Air is a poor conductor of heat, so these spaces reduce the transfer of heat from the hot surroundings into the house. As a result, hollow bricks help keep the interiors of houses cooler in hot regions.

Q8. Explain how large water bodies prevent extreme temperature in areas around them.

Large water bodies such as seas and oceans heat up and cool down more slowly than land. This difference affects the temperature of nearby areas.

During the day:

• Land heats up faster than water.

• Air above the land becomes warmer and rises.

• Cooler air from the sea moves towards the land.

• This movement is called a sea breeze.

• It helps keep nearby land areas cooler.

During the night:

• Land cools faster than water.

• Air above the sea remains relatively warmer and rises.

• Cooler air from the land moves towards the sea.

• This movement is called a land breeze.

Thus, large water bodies moderate the temperature of nearby areas and reduce extreme temperature changes.

Q9. Explain how water seeps through the surface of the Earth and gets stored as groundwater.

Answer:

Rainwater enters the ground through the pores and spaces present in soil and rocks. This process is known as infiltration.

As the water moves downwards, it fills spaces and cracks in soil and underground rocks. The accumulated water is stored below the Earth's surface as groundwater. Underground layers of rocks and sediments that can store and transmit groundwater are called aquifers.

Q10. The water cycle helps in the redistribution and replenishment of water on the Earth. Justify the statement.

Answer:

The water cycle continuously moves water between the Earth's surface and the atmosphere.

1. Water from oceans, rivers, lakes and other sources changes into water vapour through evaporation.

2. Water vapour rises and contributes to cloud formation.

3. Clouds move across different regions and release water through precipitation such as rain.

4. This movement carries water from large water bodies to different parts of the Earth, resulting in the redistribution of water.

5. Rainwater fills rivers and lakes and also seeps underground to replenish groundwater.

Therefore, the water cycle plays an important role in both redistributing and replenishing water on Earth.

NCERT Solutions for Class 7 Science Curiosity Chapter 7 PDF

Quick revision is more convenient with the textbook questions and their answers in one place. The Class 7 Science Curiosity Chapter 7 Solutions PDF includes questions related to conduction, convection, insulation, sea and land breezes, groundwater and the water cycle for easier practice and revision.

Why Choose NCERT Class 7 Science Chapter 7 Solutions by Physics Wallah?

The NCERT Class 7 Science Chapter 7 Solutions by PW make concepts related to heat transfer and natural processes easier to understand through textbook questions, everyday examples and clear explanations. Important learning areas include:

• Understand Conduction: Learn how heat travels through solids and why good conductors are used in objects that need efficient heat transfer.

• Explore Convection: Understand how the movement of warmer and cooler particles transfers heat through liquids and gases.

• Identify Insulating Materials: Learn how materials such as air and hollow bricks slow down the transfer of heat.

• Understand Sea and Land Breezes: Explore how land and water heat and cool at different rates, causing changes in air movement.

• Connect Concepts with Daily Life: Relate heat transfer to saucepan handles, cold lassi, smoke detectors and house construction.

• Learn About Groundwater: Understand how rainwater enters the ground through infiltration and gets stored below the Earth's surface.

• Understand the Water Cycle: Learn how evaporation, cloud formation and precipitation move water between different parts of the Earth.

• Practise Application-Based Questions: Use concepts related to heat, air movement and water to answer textbook and everyday-situation questions.

From the way a saucepan transfers heat to the formation of sea breezes and groundwater, Chapter 7 connects scientific concepts with processes that occur around us. The NCERT Class 7 Science Chapter 7 Solutions explain conduction, convection, insulation, heat movement and the water cycle through clear questions and examples. Revising these topics can help children understand how heat and water behave in different situations.

 Related Resources

• CBSE Class 7 Science Syllabus

• CBSE Class 7 Science NCERT Solutions

• CBSE Class 7 Science Sample Papers

• CBSE Class 7 Science Notes