NCERT solution science class 7 chapter 4 heat .

NCERT solution class 7 science ch 4 HEAT.

Here detailed answer of NCERT book class 7 science ch 4 .

Q 1
.State similaritie and difference between the laborator thermometer and the clinical thermometer.
Answer(i) Both clinical and laboratory thermometers have long, narrow, uniform glass tubes.
(ii) The bulbs of both thermometers have mercury.
Difference:
(i) The temperature range of the clinical thermometer ranges from 35 degrees Celsius to 42 degree Celsius whereas the laboratory thermometer ranges from -10 ° C to 110 ° C.
(ii) The diagnostic thermometer is used to measure the temperature of the human body.
However, laboratory thermometers can not be used to measure the temperature of the human body.
(iii) The minimum count of both the thermometer is different.
(iv) Unlike the diagnostic thermometer which can be tilted, the laboratory thermometer is kept straight while reading the temperature values.

Q 2.Give two example each of conductor and insulator  of heat.
Answer: the two examples of conductor of heat are:-
(i) steel
(ii) iron
the two examples of conductor of insulator are:-
(i) wood
(ii) paper

Q 3.fill in the blank:-
Only answer:
(a) temperature
(b) clinical
(c) Celsius
(d) radiation
(e) conduction
(f) dark

Q 4.match the followings:-
         Column I.                                  Column II
(i)land breeze blows during ------ night
(ii)sea breeze blows during------ day
(iii)dark coloured cloth are preffered during----- winter
(iv)light coloured cloth are preffered during----- summer.

Q 5.Discuss why wearing more layer of clothing during winters keeps us warmer than wearing just one thick piece of clothing.
Answer:During the winter, we prefer to wear more layers of clothing than a thick piece of clothing, because the air gets stuck between the layers of different fabrics. Due to being a poor conductor of heat, air prevents the lack of heat from our body. Therefore, the clothing layers keep us warm from one layer.

Q 6.Look at Figure. Mark where the heat is being transferred by conduction, by convection and by radiation.
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(ii) heat transfer from the pan to the water is done by the movement.
Answer:
(i) The transfer of heat from the burner to the pan is done by radiation.
(iii) The transfer of heat within the water is done by convection.

Q 7.In place of hot climate it is advised that the outer wall of house be painted white. Explain.
Answer:In warmer climatic places, it is advisable to paint the outer walls of houses as white because the light colors like white reflect the majority of the fall on it. Therefore, a light color keeps the house cool.

Q 8.One litres of water at 30°C is mixed with one litre of water at 50°C. The temperatures of the mixture will be:
Answer:(d)The temperatures of the mixture will be between 30°C and 50°C.

Q 9.An iron balls at 40°C is dropped in a mug containing water at 40°C.
Th e heat will:
Answer:(b)Th e heat will not flow from iron ball to water or from water to iron ball as both the substances have same temperature.

Q 10.A wooden spoon is dipped in a cup of ice cream. It other end;
Answer:(d)does not become cold.

End.....

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