# 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
(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