NCERT Solutions Class 7 Science Chapter 3 - Heat

In class 7 science chapter 3 heat, we are going to look at how we can find out whether an object is hot or cold and how we can measure its temperature. Heat NCERT class 7 gives a brief background on heat and its characteristics, questions that can be asked about heat, and methods of heat transfer.

The NCERT Solutions provide the students well explained solutions to all class 7 science chapter 3 questions and answers. These solutions not only help in imprinting heat NCERT class 7 basic concepts in the right mind but also are backed with well labeled diagrams. Using class 7 science chapter 3 heat question answer frequently gives the student an opportunity to assess their comprehension of the chapter. Students should be able to learn where they stand and where they need to improve on especially in understanding all concepts in the subject area. This consistent practice of NCERT Solutions for Class 7 science chapter 3 exercise not only enhances their comprehension but also builds their confidence, helping them to tackle even complex problems with ease.

1.0Download Class 7 Science Chapter 3 NCERT Solutions PDF Online

Students can download class 7 science chapter 3 NCERT solutions from the below link and practice from anywhere anytime

NCERT solutions follow the entire curriculum and therefore, these books can be very useful for revision purposes. As these solutions align with the NCERT textbook, they often reflect the types of questions that appear in final exams. This ensures that students are thoroughly prepared, and since many exam questions are directly taken from the textbook, practicing with these solutions can lead to better performance in the exams.

2.0What Will Students Learn in Chapter 3: Heat?

• Our sense of touch is not always a reliable guide to the degree of hotness of an object.  
• Temperature is a measure of the degree of hotness of an object.  
• Thermometer is a device used for measuring temperature.  
• Clinical thermometer is used to measure our body temperature. The range of this thermometer is from 35°C to 42°C. For other purposes, we use the laboratory thermometers. The range of these thermometers is usually from –10°C to 110°C.  
• The normal temperature of the human body is 37°C.  
• The heat flows from a body at a higher temperature to a body at a lower temperature. There are three ways in which heat can flow from one object to another. These are conduction, convection and radiation.  
• In solids, generally, the heat is transferred by conduction. In liquids and gases the heat is transferred by convection. 
• No medium is required for transfer of heat by radiation.  
• The materials which allow heat to pass through them easily are conductors of heat. The materials which do not allow heat to pass through them easily are called insulators.
• Dark-coloured objects absorb more heat than the light-coloured objects. That is the reason we feel more comfortable in light-coloured clothes in the summer. Woolen 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 fibers.

3.0NCERT Questions with Solutions for Class 7 Science Chapter 3 - Detailed Solutions

• State similarities and differences between the laboratory thermometer and the clinical thermometer. Solution Similarities: (i) Both clinical and laboratory thermometers have long, narrow, uniform glass tubes. (ii) The bulbs of both the thermometers have mercury in them. Differences: (i) The temperature range of clinical thermometers is from $35^{\circ }\mathrm{C}$ to $42^{\circ }\mathrm{C}$ while that of laboratory thermometer is from $-10^{\circ }\mathrm{C}$ to $110^{\circ }\mathrm{C}$. (ii) Clinical thermometer is used to measure the temperature of a human body. However, laboratory thermometer cannot be used to measure the temperature of a human body. (iii) Unlike clinical thermometer that can be tilted, laboratory thermometer is kept upright while reading the temperature values.
• Give two examples each of conductors and insulators of heat. Solution Two examples of conductors of heat are (i) Silver (ii) Iron Two examples of insulators of heat are (i) Wood (ii) Plastic
• Fill in the blanks: (a) The hotness of an object is determined by its . (b) Temperature of boiling water cannot be measured by a ___ thermometer. (c) Temperature is measured in degree . (d) No medium is required for transfer of heat by the process of _. (e) A cold steel spoon is dipped in a cup of hot milk. It transfers heat to its other end by the process of . (f) Clothes of colours absorb heat better than clothes of light colours. Solution (a) The hotness of an object is determined by its temperature. (b) Temperature of boiling water cannot be measured by a clinical thermometer. (c) Temperature is measured in degree Celsius. (d) No medium is required for transfer of heat by the process of radiation. (e) A cold steel spoon is dipped in a cup of hot milk. It transfers heat to its other end by the process of conduction. (f) Clothes of dark colours absorb heat better than clothes of light colours.
• Match the following

Solution $(\mathrm{A})\to \mathrm{p},(\mathrm{B})\to \mathrm{q},(\mathrm{C})\to \mathrm{r}$, (D) $\to s$

• Discuss why wearing more layers of clothing during winters keeps us warmer than wearing just one thick piece of clothing. Solution During winters, we prefer wearing more layers of clothing than just one thick piece of clothing because air gets trapped in between the various clothing layers. Being a poor conductor of heat, air prevents heat loss from our body. Hence, layers of clothing keep us warmer than a single layer.
• Look at Figure. Mark where the heat is being transferred by conduction, by convection and by radiation.

• Solution (i) Transfer of heat from burner to pan is by radiation. (ii) Transfer of heat from pan to water is by conduction. (iii) Transfer of heat within water is by convection.
• In places of hot climate it is advised that the outer walls of houses be painted white. Explain. Solution In places of hot climate, it is advised to paint the outer walls of houses as white because a light colour such as white reflects back most of the heat that falls on it. Hence, a light colour tends to keep the house cool.
• One litre of water at $30^{\circ }\mathrm{C}$ is mixed with one litre of water at $50^{\circ }\mathrm{C}$. The temperature of the mixture will be (1) $80^{\circ }\mathrm{C}$ (2) more than $50^{\circ }\mathrm{C}$ but less than $80^{\circ }\mathrm{C}$ (3) $20^{\circ }\mathrm{C}$ (4) between $30^{\circ }\mathrm{C}$ and $50^{\circ }\mathrm{C}$ Solution Option (4) The temperature of the mixture will be between $30^{\circ }\mathrm{C}$ and $50^{\circ }\mathrm{C}$.
• An iron ball at $40^{\circ }\mathrm{C}$ is dropped in a mug containing water at $40^{\circ }\mathrm{C}$. The heat will (1) flow from iron ball to water. (2) not flow from iron ball to water or from water to iron ball. (3) flow from water to iron ball. (4) increase the temperature of both. Solution Option (2) The heat will not flow from iron ball to water or from water to iron ball as both substances have same temperature.
• A wooden spoon is dipped in a cup of ice cream. Its other end. (1) becomes cold by the process of conduction. (2) becomes cold by the process of convection. (3) becomes cold by the process of radiation. (4) does not become cold. Solution Option (4) Its other end does not become cold as wood is a bad conductor of heat.