SAQ for Chapter 7 Heat Transfer in Nature Class 7 Science NCERT
Important Questions1
Q1: Define heat.
Answer
Heat is a form of energy which produces a sensation of warmth and flows when there is a temperature difference between two bodies. It is measured in joules or calories.
SAQ
2
Q2: Define temperature. What is its unit?
Answer
A reliable measure of the hotness of an object is its temperature. Temperature is measured by a device called a thermometer. The unit of temperature is degree Celsius (°C), Fahrenheit, and Kelvin (SI unit).
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3
Q3: What is the use of the maximum-minimum thermometer?
Answer
The maximum-minimum thermometer is used to measure the highest and lowest temperatures of a place in a day. It is commonly used in weather stations to track daily temperature variations. This thermometer helps in understanding temperature fluctuations, which is essential for weather forecasting and analysis.
Max-min Thermometer
SAQ
4
Q4: : What is conduction?
Answer
Heat flows from a hotter object to a colder object. The process by which heat is transferred from the hotter end to the colder end of an object is known as conduction.
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5
Q5: Why conduction is only possible in solids?
Answer
In solids, generally, the heat is transferred by the process of conduction because particles of solids are closely packed, and heat is transferred from the hotter end to the colder end of an object.
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6
Q6: How does the heat from the sun reach us?
Answer
Heat from the sun reaches us by radiation, which does not require a medium to transfer heat. Unlike conduction (which occurs in solids) and convection (which occurs in liquids and gases), radiation can transfer heat even through the vacuum of space
SAQ
7
Q7: Explain how water is heated by convection.
Answer
The water is a poor conductor of heat, so do not heat it by conduction. When water is heated, the water becomes lighter. Hot water rises up. The cold water from the sides moves down towards the source of heat. This water also gets hot and rises upward, and water from the sides moves down. This process continues till the whole water gets heated. This mode of heat transfer is known as convection.
SAQ
8
Q8: Differentiate between conductor and insulators?
Answer
The materials which allow heat to pass through them easily are conductors of heat. For example, aluminum, iron, and copper The materials that do not allow heat to pass through them easily are poor conductors of heat, known as insulators, such as plastic and wood.
SAQ
9
Q9: Explain land breeze.
Answer
The water cools down more slowly at night than the land. So, the cool air from the land moves towards the sea. This is called the land breeze.
SAQ
10
Q10: Explain sea breeze.
Answer
During the day, the land gets heated faster than the water. The air over the land becomes hotter and rises up. The sea's cooler air rushes towards the land to take its place. The warm air from the land moves towards the sea to complete the cycle. The air from the sea is called the sea breeze.
SAQ