Heat transfer in nature solutions Class 7 Curiosity NCERT
30 October
Class 7 Curiosity – Heat Transfer in Nature solutions
🔥 Class 7 Curiosity – Heat Transfer in Nature
Have you ever wondered why your metal spoon gets hot when left in hot soup? Or why smoke from a fire always rises upward? 🌪️ What makes water in a kettle heat up so quickly? These are not just everyday happenings – they’re windows into the fascinating world of heat transfer!
In this chapter, we’ll explore how heat moves through solids, liquids, and gases. With simple explanations, real-life examples, and eye-opening questions, you're about to uncover the invisible ways heat travels around us. Let's dive in and uncover the science that warms our world! 🌎✨
In-Text Questions
1. How does heat get transferred in materials?
Heat is transferred in materials by different processes called conduction, convection and radiation.
In solids, particles are closely packed, the heat transfer will takes place with out the motion of particles of the medium which is known as Conduction.
In liquids and gases particles are free to move, heat transfer will takes place along with the motion of particles which is known as Convection.
Heat can also be transferred without any medium which is known as Radiation.
For example: Heat transfer from the sun to the earth.
2. Why is the smoke going up?
Smoke goes up because the hot air carrying it becomes lighter and less dense. This hot air rises above the cooler air, causing the smoke to move upwards. This is an example of convection in gases.
3. How does heat transfer take place in liquids? Do liquids also rise up when heated like air?
Yes, heat transfer in liquids happens by convection. When a liquid is heated, the lower layers become hot, expand, and become lighter. They rise while the cooler liquid moves down. This circular movement is called a convection current, just like in air.
4. I wonder how heat from the fire reaches us?
Heat from the fire reaches us through radiation. This is a form of heat transfer where energy travels in the form of invisible waves and does not need any medium (like air or water). That’s why you feel warm even when you're standing a little away from a fire.
5. How does water seep through the surface of the Earth?
Water seeps into the ground through tiny gaps in the soil and rocks. This process is called infiltration. The soil absorbs the water like a sponge, and it slowly moves deeper to collect underground as groundwater.
Exercise Questions
1. (i) Your father bought a saucepan made of two different materials, A and B. The materials A and B have the following properties —
Correct Answer: (c) A is a good conductor and B is a poor conductor of heat.
Explanation: The base (A) of the pan should be a good conductor to heat food efficiently, while the handle (B) is a poor conductor to prevent burns when holding the pan.
Explanation: The base (A) of the pan should be a good conductor to heat food efficiently, while the handle (B) is a poor conductor to prevent burns when holding the pan.
1. (ii) Pins are stuck to a metal strip with wax. A burning candle is placed under the strip. Which of the following will happen?
Correct Answer: (b) Pins I and II will fall earlier than pins III and IV.
Explanation: Heat conducts from the point above the candle, reaching pins I and II faster, melting the wax and causing them to fall first.
Explanation: Heat conducts from the point above the candle, reaching pins I and II faster, melting the wax and causing them to fall first.
1. (iii) Where should a smoke detector be placed in your room?
Correct Answer: (c) On the ceiling.
Explanation: Hot air and smoke rise upwards, so placing the detector on the ceiling allows it to detect smoke quickly.
Explanation: Hot air and smoke rise upwards, so placing the detector on the ceiling allows it to detect smoke quickly.
2. Will a clay tumbler help keep the lassi cold longer?
Answer: Yes, a clay tumbler helps in keeping lassi cold longer. Clay is porous and allows evaporation of water from its surface, causing cooling. This natural cooling effect helps maintain the low temperature of the drink.
3. True or False
(i) Heat transfer takes place in solids through convection. [ False ]
(ii) Heat transfer through convection takes place by the actual movement of particles. [ True ]
(iii) Areas with clay materials allow more seepage of water than those with sandy materials. [ False ]
(iv) The movement of cooler air from land to sea is called land breeze. [ False ] (It is called sea breeze.)
(ii) Heat transfer through convection takes place by the actual movement of particles. [ True ]
(iii) Areas with clay materials allow more seepage of water than those with sandy materials. [ False ]
(iv) The movement of cooler air from land to sea is called land breeze. [ False ] (It is called sea breeze.)
4. Where do ice cubes get heat from in water?
Answer: The ice cubes absorb heat from the surrounding water. Heat flows from the warmer water to the colder ice cubes until thermal equilibrium is reached. This causes the ice to melt.
5. Smoke from incense stick — movement and direction?
Answer: The smoke will rise upward and spread sideways. Since hot air rises, the smoke also moves upward with the air currents. This movement can be represented with an upward arrow in the diagram.
6. Which thermometer will record a higher temperature in Fig. 7.16?
Answer: Thermometer in Fig. 7.16(b) will record a higher temperature.
Explanation: Heat transfer in liquids occurs through convection. In Fig. 7.16(b), the thermometer is placed vertically above the flame, where hot water rises and transfers heat to the bulb directly.
Explanation: Heat transfer in liquids occurs through convection. In Fig. 7.16(b), the thermometer is placed vertically above the flame, where hot water rises and transfers heat to the bulb directly.
7. Why are hollow bricks used to construct the outer walls of houses in hot regions?
Answer: Hollow bricks contain air gaps, and air is a poor conductor of heat. These bricks reduce heat transfer from the outside to the inside of houses, keeping the interiors cooler in hot climates.
8. Explain how large water bodies prevent extreme temperature in areas around them.
Answer: Water has a high specific heat capacity, which means it heats up and cools down slowly. Large water bodies absorb heat during the day and release it slowly at night, helping to maintain moderate temperatures in nearby areas.
9. Explain how water seeps through the surface of the Earth and gets stored as groundwater.
Answer: Rainwater or water from other sources seeps through the pores and spaces in the soil and rocks. This process is called infiltration. The water continues to move downward and gets stored in underground layers called aquifers, forming groundwater.
10. The water cycle helps in the redistribution and replenishment of water on the Earth. Justify the statement.
Answer: The water cycle involves continuous movement of water through processes like evaporation, condensation, precipitation, and infiltration. It redistributes water across the Earth’s surface and underground, replenishing sources such as rivers, lakes, and groundwater, ensuring the availability of water for all living organisms.
🌟 Final Words of Inspiration
Learning science is not just about reading books — it's about observing, questioning, and exploring the world around us. You’ve just taken another powerful step toward understanding nature's amazing processes. Stay curious, ask why, and never stop wondering — because the world is full of answers waiting to be discovered by minds like yours! 🔍🌍
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