Tuesday, 12 April 2016

TEXTBOOK ANSWERS AND SOLUTIONS OF CBSE CLASS VII SCIENCE Chapter 4 Heat





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

ANSWER:-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) Clinical thermometer is used to measure the temperature of a human body.
ii) The least count of both the thermometers differs.

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



ANSWER:-Two examples of conductors of heat are:
(i) Aluminium
(ii) Iron
Two examples of insulators of heat are:
(i) Wood
(ii) Plastic

3) Fill in the blanks:
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.

4) Match the following:
(i) Land breeze blows during.                                                             (d) night
(ii) 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 winters keeps us warmer than wearing just one thick piece of clothing.




ANSWER:-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.







7) 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 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.

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

ANSWER: - (d)

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

ANSWER:-(b)

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.


ANSWER:- (d)
Written By Badal Paul
The author is a passionate blogger, writer and educationalist. This blog is created to ease troubles of the Cbse students. The author holds multiple blogs and the writer of the Novel KALCHAKRA, OOM AND THE CHOSEN FIVE.