NCERT solution for class 7th //Science // Chapter 4 - Heat

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NCERT solution for class 7th //Science // Chapter 4 - Heat

Chapter 4 - Heat

Exercise 

Q1 State similarities and differences between the laboratory thermometer and the clinical thermometer 

Answer 

Similarities 

• Both thermometer use Celsius scale on the glass tube 
• In both a thermometer contain Mercury it bulb
• Both thermometer consists of a long narrow glass tubes
• In both thermometer have a bulb at one end 

Differences 

• Clinical thermometer has a kink near to the bulb while in laboratory thermometer it is absent 
• Clinical thermometer reads the temperature range 35 °C to 45 °C while the range of laboratory thermometer is -10 °C to 110°C degree

Q2. Give examples each of conductors and insulators of heat 

Answer 

Conductor of heat  - Aluminium ,Iron ,Copper . 

Insulator of heat  - Wood , Plastic 

Q3. 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 heat is transferred to its other end by the process of conduction 

f) Clothes of dark colours absorb more heat Celsius better than the clothes of light colour 

Q4 .

Match the following 

   Column  A                                      Column B

a) Land breeze blows during           Summer 

b) Sea breeze blows during               Winter 

c) Dark coloured clothes 

are preferred during.                           Day 

d) Light coloured clothes 

are preferred during                          Night  

Answer  

 Column  A                                      Column B

a) Land breeze blows during           Night

b) Sea breeze blows during              Day

c) Dark coloured clothes 

are preferred during.                           Winter

d) Light coloured clothes 

are preferred during                        Summer

Q5 Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one click piece of clothing 

Answer 

More layers of clothing keeps us warm during the winter because in between that space the air is present and air is a bad conductor of heat so it keeps the body warm

Q6 . Look at figure 4.13 mark where the heat is being transferred by conduction convection and radiation 

Answer 

Q7 . In places of hot climate it is advised that the outer walls of houses be painted white explain 

Answer 

In places of hard climate it is advised that the outer walls of houses be painted white because white colour reflects the heat and it do not increase the temperature inside the house

Q8 . One litre of water at 30 °C is mixed with one litre of water at 30 °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

Q9. 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) Increases the temperature of both 

Answer - 

Not flow from iron ball to water form water to iron ball

Q10 . A wooden spoon is dipped in a cup of ice cream its other 

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 -  

Does not become cold

Q11. Stainless steel pans are actually provided with copper bottom the reason for this could be that 

a) Copper bottom makes the pain 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 

Answer - 

 Copper is better conductor of heat than stainless steel