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Chapter 1: Nutrition in Plants

Chapter 2: Nutrition in Animals

Chapter 3: Fibre to Fabric

Chapter 4:Heat

Chapter 5: Acids, Bases and Salts

Chapter 6: Physical and Chemical Changes

Chapter 7: Weather, Climate and Adaptations of Animals to Climate

Chapter 8: Winds, Storms and Cyclones

Chapter 9:Soil

Chapter 10: Respiration in Organisms

Chapter 11:Transportation in Animals and Plants

Chapter 12:Reproduction in Plants

Chapter 13:Motion and Timers

Chapter 14: Electric Current and Its Effects

Chapter 15:Light

Chapter 16:Water: A Precious Resource

Chapter 17: Forests: Our Lifeline

Chapter 18: Wastewater Story

NCERT Solutions for Class 7 science chapter 4

Heat

NCERT Solutions for class 7 science chapter 4 Exercise Question

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

Answer

Similarities

  • Both consists of a long, narrow, uniform glass tube
  • both have a bulb at one end.
  • Bulbs of both the thermometers consist of mercury
  • The scale of both the thermometerwe use celsius scale, indicated by °C.

Differences

  • Temperature range of clinical thermometer is 350C to 420C While Temperature range of laboratory thermometer is -100C to 110 0C
  • The clinical thermometer is used to measure body temperature, however, laboratory thermometer is Used to measure temperature in the laboratory

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

Answer

Conductors: Silver and Copper

Insulators: Paper and wood

Question 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.

Answer

(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 Celcius.

(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 darkcolours absorb more heat better than clothes of light colours.

Question 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
Answer
(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

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

Answer

More layers of clothing during winter keeps us warmer because as they have a lot of space between them and air gets trapped between layer. As air is a bad conductor of heat it does not allow the escape of the heat out of the body.

Question 6
Look at Fig. 4.13. Mark where the heat is being transferred by conduction, by convection and by radiation.


Answer


Question 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 that the outer walls of houses be painted white because white colour is best reflected colour and poor absorber of heat. So the houses do not heat up too much

Question 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

between 30°C and 50°C .

Question 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) not flow from iron ball to water or from water to iron ball

Question 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) does not become cold because wood is a bad conductor of heat.

Question 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 stainless steel.

(d) copper is easier to clean than stainless steel.

Answer

(c) copper is a better conductor of heat than the stainless steel.