CHAPTER 4
HEAT
Here is some important points and answer of chapter 4 Heat NCERT science of class 7 which helps students to better understand topics of chapter 4 Heat.
Important Points:-
I) Conduction:- The process by which heat is transferred from the hotter end its colder end of an object is known as Conduction.
2) Conductor:- Material which allow to heat pass through them easily are known as conductor.
3) Convection:- The process by which heat is transmitted in liquid and gas through any medium is known as convection.
4)Insulator:- Material which do not allow to hear pass through them easily are known as insulator. Example:- wood, plastic etc.
5) Land breeze:- During night when hot air rise from sea surface and cold air of land surface move towards sea surface known as land breeze.
6) Radiation:- When the heat is transfer in surrounding without any medium is known as radiation.
7)Sea breeze:- During day time when cold air of sea surface move towards land surface is known sea breeze.
8) Thermometer:- A device which is used for measuring temperature of object is known as thermometer.
These are the important keynotes of Chapter 4 Heat.
Here is the Solution Of textbook CHAPTER 4
Heat.
Exercise Questions-
Ques 1. State similarities and differences between the laboratory thermometer and the clinical thermometer.
Ans.Similarities
a) Both the thermometer have a bulb at the end.
b) Both of them have a long, narrow and uniform glass tube.
c)They have common scale(celsius) and use mercury as thermometeric liquid.
Difference
a)A clinical thermometer is designed to measure the temperature of a human body while the laboratory thermometer is used to measure temperature of other objects.
b) A clinical thermometer reads temperature from 35°C to 42°C while the range of a laboratory thermometer is from -10°C to 110°C.
c)A clinical thermometer has a kink while a laboratory thermometer does not.
Ques 2. Give two examples each of conductors and insulators of heat.
Ans. Examples of Conductors:- Metals like iron and Copper.
Examples of insulators:- Wood and plastic.
Ques 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. It transfers heat to its other end by the process of __________.
f)Clothes of ________ colours absorb heat better than clothes of light colours.
Ans. a) thermometer
b)clinical
c) celsius
d) radiation
e) conductor
f) dark
Ques 4. Match the following:-
i) land breeze blows during. a)summer
ii)Sea breeze blows during b) winter
iii)Dark coloured clothes are (c)day
preferred during
iv)light Colured clothes are (d)Night
preferred during
Ans.i) night
ii) day
iii) winter
iv) summer
Ques 5. Discuss why wearing more layers of clothing during winter keep us warmer than wearing just one thick piece of clothing.
Ans. Air is trapped between the layers of clothes.
As air is a bad conductor of heat, it prevents the flow of heat from our body to the surroundings and hence,we feel warm. If the layers of clothing are more,the thickness of the air layers too increase and is more effective in preventing the heat flow from our body to the surroundings.
Ques 6. Look at Fig. 4.13. Mark where the heat is being transferred by conduction, by convection and by radiation.
Ans.
Ques 7. In places of hot climate it is advised that the outer walls of houses be paint white. Explain.
Ans. In places of hot climate it is advised that the outer walls of houses be painted white. As white colour reflectment of the light incident on it. It makes the house cool during hot climate.
Ques 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.
Ans. Between 30°C and 50°C.
Ques 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.
Ans. Flow from iron ball to water.
Ques 10. A wooden spoon is dipped in a cup of icecream. 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.
Ans. Does not become cold.
Ques 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 the stainless steel.
d)Copper is easier to clean than the stainless steel.
Ans. c)copper is a better conductor of heat than the stainless steel.
THE SOLUTION OF CHAPTER 4 HEAT OF SCIENCE NCERT OF CLASS 7 IS GIVEN ACCORDING TO LATEST SYLLABUS CBSE.
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