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NCERT Solutions for Class 7 Science Chapter 4: Heat

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NCERT Solutions for Class 7 Science Chapter 4 Heat is provided below to help students of class 7 understand the concepts of Heat interactively. The NCERT solutions for class 7 science chapter 4 Heat is one of the most crucial chapters in class 7 science. Heat is a very basic topic that is necessary for the students to understand to score well in the exams and to face bigger challenges in the future.

NCERT Solutions for Class 7 Science Chapter 4 by Swiflearn are by far the best and most reliable NCERT Solutions that you can find on the internet. These NCERT Solutions for Class 7 Science Chapter 4 are designed as per the CBSE Class 7 Science Syllabus. These NCERT Solutions will surely make your learning convenient & fun. Students can also Download FREE PDF of NCERT Solutions Class 7 Science Chapter 4.

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NCERT Solutions for Class 7 Science Chapter 4 Heat PDF

1. State similarities and differences between the laboratory thermometer
and the clinical thermometer.

Solution:
The similarities between laboratory thermometer and clinical thermometer are as follows:
(i) Both consist of a long, narrow, uniform glass tube and a bulb at one end.
(ii) Both contain mercury in the bulb.
(iii) Both have Celsius scale on the glass tube.
The differences between laboratory thermometer and clinical thermometer are as follows:

Clinical thermometer                                          Laboratory thermometer
It can measure temperature ranging from
35°C to 42°C.                                                  It can measure temperature ranging                                                                          from 10°C to 110°C.
It is used to measure temperature of human
body.                                                                It is used to measure temperature of
experimental objects on laboratory.
It has a kink which prevents the immediate
back flow of mercury.                                        It does not have a kink.

2. Give two examples each of conductors and insulators of heat.

Solution:
Iron and copper are examples of conductors of heat whereas wood and plastic are insulators
of heat.

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 steel spoon 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.

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. Heat is transferred to its other end by the process of conduction.
(f ) Clothes of dark colours absorb more heat better than clothes of light colours.

4. Match the following:
Land breeze blows during                         Summer
Sea breeze blows during                           Winter
Dark coloured clothes are
preferred during                                          Day
Lightcoloured clothes are
preferred during                                          Night

Solution:
Land breeze blows during                              Night
Sea breeze blows during                                Day
Dark coloured clothes are preferred
during                                                              Winter
Light coloured clothes are preferred
during                                                              Summer

5. Discuss why wearing more layers of clothing during winter keeps us
warmer than wearing just one thick piece of clothing.

Solution:
Wearing more layers of clothing during winter keeps us warmer than one thick piece of clothing because air is trapped in-between the various layers. Air being a bad conductor of heat does not allow the heat to escape from the body.

6. Look at Fig. 4.13. Mark where the heat is being transferred by
conduction, by convection and by radiation.(Refer PDF)

Solution: Refer pdf.

7. 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 light colours reflect most of the heat falling on them. Thus, the white walls will absorb less amount of heat and keeps the house cool.

8. One litre of water at 30°C is mixed with one litre of water at 50°C. The
temperature of the mixture will be
(a) 80°C
(b) more than 50°C but less than 80°C
(c) 20°C
(d) between 30°C and 50°C

Solution:
Option (d) is correct because the heat gained by cold water and the lost by hot water will be equal. This means that the final temperature of the mixture will be between 30°C and 50°C.

9. An iron ball at 40°C is dropped in a mug containing water at 40°C. 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.

Solution:
Option (b) is correct as heat transfer takes place only when two objects at different temperatures are brought in contact.

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.

Solution:
Option (d) is correct because wood is an insulator of heat.

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.

Solution:
Option (c) is correct because copper is a better conductor of heat than the stainless steel.

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