Here are the NCERT Solutions for Class 7 Science Chapter 3: Heat, designed to help students grasp the concepts of heat in an engaging and interactive way. These solutions are an essential resource for excelling in Class 7 Science. Understanding the topic of heat is crucial for scoring well in exams and preparing for more advanced challenges in the future.
NCERT Solution for Class 7 Science Chapter 4 - Heat
Exercise Questions
1. State similarities and differences between the laboratory thermometer and the clinical thermometer.
Answer :
Similarities between the laboratory thermometer and clinical thermometer :
1. Both thermometers are constructed from glass and have a long, narrow glass tube.
2. Each thermometer has a bulb at one end.
3. The bulbs of both thermometers contain mercury.
4. Both thermometers use the Celsius scale for measurements.
Differences between the laboratory thermometer and clinical thermometer :
| Clinical Thermometer | Laboratory thermometer |
|---|---|
| The temperature range is from 35°C to 42°C | The temperature range is from -10°C to 110°C |
| Used to measure human body temperature | Used to measure temperature in the laboratory |
| It has a kink that prevents the immediate backflow of mercury | It does not have a kink |
2. Give two examples each of the conductors and insulators of heat.
Answer :
Conductors: Iron and copper
Insulators: Plastic and wood
3. 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 spoon steel is dipped in a cup of hot milk. Heat is transferred to its other end by the process of .....................
(f) Clothes of ................ colours absorb more heat better than clothes of light colours.
Answers :
(a) temperature
(b) clinical
(c) celcius
(d) radiation
(e) conduction
(f) dark
4. Match the following :
| (i) Land breeze blows during | (a) summer |
| (ii) Sea breeze blows during | (b) winter |
| (iii) Dark coloured clothes are preferred during | (c) day |
| (iv) Light coloured clothes are preferred during | (d) night |
Answers :
| (i) The land breeze blows during | (d) night |
| (ii) The sea breeze blows during | (c) day |
| (iii) Dark coloured clothes are preferred during | (b) winter |
| (iv) Light coloured clothes are preferred during | (a) summer |
5. Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.
Answers :
Wearing multiple layers of clothing in winter keeps us warmer than a single thick piece because the air trapped between the layers acts as an insulator. Since air is a poor conductor of heat, it prevents body heat from escaping.
6. Look at Fig. 3.13. Mark where the heat is being transferred by conduction, by convection and by radiation.
Answers :
7. In places of hot climate it is advised that the outer walls of houses be painted white. Explain.
Answers :
In hot climates, it is recommended to paint the exterior walls of houses white. This is because white reflects heat, helping to keep the houses cooler.
8. One litre of water at 30℃ is mixed with one litre of water at 50℃. The temperature of the mixture will be
(a) 80℃ (b) more than 50℃ but less than 80℃
(c) 20℃ (d) between 30℃ and 50℃
Answers :
(d) between 30℃ and 50℃
9. An iron ball at 40℃ is dropped in a mug containing water at 40℃. The heat will
(a) flow from iron ball to water
(b) not flow from iron ball to water or from water to iron ball.
(c) flow from water to iron ball.
(d) increase the temperature of both.
Answer :
(b) not flow from iron ball to water or from water to iron ball
10. A wooden spoon is dipped in a cup of ice cream. Its other end
(a) becomes cold by the process of conduction.
(b) becomes cold by the process of convection
(c) becomes cold by the process of radiation.
(d) does not become cold.
Answers :
(d) does not become cold
11. Stainless steel pans are usually provided with copper bottoms. The reason for this could be that
(a) copper bottom makes the pan more durable
(b) such pans appear colourful
(c) Copper is a better conductor of heat than the stainless steel.
(d) Copper is easier to clean than the stainless steel.
Answer :
(c) Copper is a better conductor of heat than the stainless steel