Heat Important Questions Class 7 Science Chapter 4
Heat Class 7 Science Chapter 4 Important Questions and Answers are provided here. We prepared these extra questions based on the latest NCERT Class 7 Science Book. These important questions will help you to properly understand a particular concept of the chapter. Practicing class 7 important questions before the exam will help you to get excellent marks in the exam.
Class 7 Science Chapter 4 Heat Important Questions
Very Short Answer Type Question
1: Define temperature.
Answer: A reliable measure of the hotness of an object is its temperature.
2: Name the device used to measure temperature.
Answer: Thermometer.
3: Name the two types of thermometer.
Answer: Clinical thermometer and laboratory thermometer.
4: What do you mean by clinical thermometer?
Answer: Thermometer means to measure our body temperature is called clinical thermometer.
5: The bulb in thermometer contains _____________.
Answer: Mercury.
6: Thermometer should be washed before and after use with, preferably with an _________ solution.
Answer: Antiseptic solution
7: Before use the mercury level of thermometer should be below_________________________.
Answer: 35°C
8: We should hold the thermometer by the bulb while holding it. True/False.
Answer: False
9: What is the unit of temperature as adopted by India?
Answer: Degree Celsius (°C )
10: What is the average body temperature of a healthy person?
Answer: 37°C
11: What is the range of laboratory thermometer?
Answer: – 10°C to 110°C
12: Laboratory thermometer should be kept upright and not tilted. True/False.
Answer: True.
13: The bulb of laboratory thermometer should not touch the surface of the ________________.
Answer: Container.
14: What is the use of kink in a clinical thermometer?
Answer: Kink prevents mercury level from falling on its own.
15: Give an example to show the transfer from heat from one body to another.
Answer: Any utensil kept on flame, becomes hot because heat transfers from flame to the utensil.
16: Heat always flows from a hotter object to ________________________.
Answer: Colder object.
17: Give examples of conductors.
Answer: Aluminium, copper, iron etc.
18: Give examples of insulators.
Answer: Water, air, etc.
19: Insulators are ________ conductor of heat.
Answer: Poor
20: Conductors are _____________ conductor of heat.
Answer: Good
21: Name the process by which heat transfer in air.
Answer: Convection.
22: From the sun the heat comes to us by the process called __________________.
Answer: Radiation.
23: Transfer of heat by radiation requires any medium or not?
Answer: Not.
24: All hot bodies __________________ heat.
Answer: Radiates.
25: An iron rod at 30°C is dropped by chance into a bucket containing water at 30°C, the heat will flow or not in this case?
Answer: No.
26: Which of the two absorbs more radiation- a dark coloured object or a light coloured object?
Answer: A dark coloured object.
27: Temperature of boiling water cannot be measured by a ________________________.
Answer: Clinical thermometer.
28: Land breeze blows at the time of ______________.
Answer: Night.
29: Sea breeze blows at the time of ______________.
Answer: Day
30: Which type of cloth should be preferred in the month of June?
Answer: Light coloured clothes
31: Which type of cloth should be preferred in the month of January?
Answer: Dark coloured clothes.
32: A cold steel spoon is dipped into a cup of hot coffee, it will transfer heat to its other end or not? If yes then by which process?
Answer: Yes, by conduction.
Short Answer Type Questions
1: Define heat.
Answer: Heat is a form of energy, entry or exit of which correspondingly increases or decreases internal energy of a body when no work is done on the body or by the body. It is measured in joule or calories.
2: 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 thermometer. Unit of temperature is degree Celsius (°C), Fahrenheit and Kelvin (SI unit).
3: What is the use of the maximum – minimum thermometer?
Answer: Different types of thermometers are used for different purposes. The maximum and minimum temperatures of the previous day, reported in weather reports, are measured by a thermometer called the maximum – minimum thermometer.
4: Why does the mercury not fall or rise in a clinical thermometer when taken out of the mouth?
Answer: Kink prevents mercury level from falling on its own.
5: Why clinical thermometer ranges from 35°C to 42°C?
Answer: The normal temperature of human body is 37°C.The temperature of human body normally does not go below 35°C or above 42°C. That is the reason that a clinical thermometer has the range 35°C to 42°C.
6: 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.
7: 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.
8: How does the heat from the sun reach us?
Answer: It cannot reach us by conduction or convection as there is no medium such as air in most part of the space between the earth and the sun. From the sun the heat comes to us by a different process known as radiation which does not require any medium for heat transfer.
9: Differentiate between conductor and insulators?
Answer: The materials which allow heat to pass through them easily are conductors of heat. For examples, aluminium, iron and copper The materials which do not allow heat to pass through them easily are poor conductors of heat known as insulators such as plastic and wood.
10: Explain land breeze.
Answer: At night, the water cools down more slowly than the land. So, the cool air from the land moves towards the sea. This is called the land breeze.
11: Explain sea breeze.
Answer: During the day, the land gets heated faster than the water. The air over theland becomes hotter and rises up. The cooler air from the sea rushes in 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.
12: In summer we prefer light-coloured clothes and in winter we usually wear dark-coloured clothes. Explain Why?
Answer: Dark surfaces absorb more heat and, therefore, we feel comfortable with dark coloured clothes in the winter whereas light coloured clothes reflect most of the heat that falls on them and, therefore, we feel more comfortable wearing them in the summer.
13: Why one thick blanket is less warm up than two thin blankets joined together?
Answer: There is a layer of air in between the blankets. Since air is bad conductor of heat prevent body heat to escape out, two thin blankets provides more heat than one thick blanket.
14: How Woollen clothes keep us warm in winter?
Answer: Woollen clothes keep us warm during winter. It is so because wool is a poor conductor of heat and it has air trapped in between the fibres.
17: What is the unit of heat?
Answer: Units of Heat
(a) C.G.S. unit of heat is Calorie.
(b) The M.K.S. or S.I. unit of heat is Joule
“1 calorie equals 4.18 or 4.2 joules approximately.”
18: Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.
Answer: In between the layers of cloths there is trapped air. As air is bad conductor of heat so the outside low temperature does not get transferred to body as well as prevent our body heat to escape outside. Hence more layers of cloths keep us warmer during cold winter.
19: In places of hot climate it is advised that the outer walls of houses be painted white. Explain.
Answer: In places of hot climate it is advised that the outer walls of houses be painted white because a light colour absorbs very less radiant heat and we feel comfortable inside such houses due to lower temperature inside house.
20: How heat and temperature of substance are related to each other.
Answer: Heat is the total energy of the molecular motion of the substance and temperature is the measure of average energy of the molecular motion in the substance. When we heat a substance it increases the motion of vibrating molecules of the substance thereby increasing the temperature of the substances.
21: Define specific heat.
Answer: Specific heat is a fundamental property of matter. An equal mass of different materials absorb or give out different quantities of heat, even if they are heated or cooled through the same range of temperature. This is also called specific heat capacity (abbreviated as SHC) in S.I. system.
22: What you should choose in winter one thick blanket or two thin blankets joined together? And why?
Answer: There is a layer of air in between the blankets. Since air is bad conductor of heat prevent body heat to escape out, two thin blankets provides more heat than one thick blanket.
23: What is thermal equilibrium?
Answer: Heat always from a body of higher temperature to a body of lower temperature, until the temperature of both bodies are equal, then the two bodies are said to be in thermal equilibrium.
24: Which property of liquids is used in making thermometer?
Answer: The property of thermal expansion of liquids is used in making thermometers. It states liquid expands on heating and contracts on cooling.
Long Answer Type Questions
1: Explain how water heated by convection?
Answer: The water is poor conductor of heat so do not heated by conduction. When water is heated, the water became 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.
2: What is the Relation between Celsius, Fahrenheit and Kelvin scales?
Answer: Since the range of temperature from ice-point to steam-point is equal in all the three scales, 100 centigrade degrees = (212 – 32) or 180 Fahrenheit degrees = (373 – 273) or 100 absolute degrees. We consider three thermometers in the above three scales are dipped simultaneously in a liquid of certain temperature. Let the temperatures recorded in the Celsius, Fahrenheit and Kelvin thermometers respectively be C, F and K. Now it can be proved that C / 5 = F- 32 / 9 = K- 273 /5.
3. State similarities between the laboratory thermometer and the clinical thermometer.
Answer:
- Laboratory thermometer and the clinical thermometer consist of a long, narrow, uniform glass tube.
- Laboratory thermometer and the clinical thermometer have a bulb containing mercury at the end of the tube.
- Laboratory thermometer and the clinical thermometer are marked with Celsius scale on the glass tube.
4: State differences between laboratory thermometer and clinical thermometer.
Answer:
| Clinical thermometer | Laboratory thermometer |
| It is used to measure the temperature of human body only | It is used to measure the temperature of different objects in laboratory and factories |
| It has temperature range from 35°C. to 42°C. | It has temperature range from -10°C to 110°C. |
| It has a small constriction near the mercury bulb | Usually, it does not have any constriction |
| It can be tilted while taking reading | It has to be kept upright while taking the reading |