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Selina solutions for Class 8 Physics chapter 6 - Heat Transfer

Selina Concise Physics - Middle School for Class 8 (2018-19 Session)

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Selina Selina Concise Physics - Middle School Class 8 (2018-19 Session)

Selina Concise Physics - Middle School for Class 8 (2018-19 Session)

Chapter 6: Heat Transfer

Chapter 6: Heat Transfer solutions [Page 0]

Write true or false 

Evaporation is rapid on a wet day.

Write true or false 

Evaporation takes place only from the surface of liquid.

Write true or false 

All molecules of a liquid take part in the process of evaporation.

 

Write true or false

Temperature of a liquid rises during boiling or vaporization

 Write true or false 

All molecules of a liquid take part in boiling.

Write true or false

Boiling is a rapid phenomenon.

Write true or false

All solids expand by the same amount when heated to the same rise in temperature.

Write true or false

Telephone wires are kept tight between the two poles in winter.

Write true or false 

Equal volumes of different liquids expand by the different amount when they are heated to the same rise in temperature.

Write true or false 

Solids expand the least and gases expand the most on being heated.

Write true or false

A mercury thermometer makes use of the property of expansion of liquids on heating.

Write true or false 

Kerosene contracts on heating.

Fill in the blank

Boiling occurs at ....................

Fill in the blank

Evaporation takes place at ................. .

Fill in the blank

The molecules of liquid .............heat from surroundings in evaporation.

Fill in the blank 

Heat is ...................during boiling.

Fill in the blank

Cooling is produced in ....................

Fill in the blank 

A longer rod expands ...........than a shorter rod on being heated to the same temperature.

Fill in the blank 

Liquids expand................ than the solids.

Fill in the blank

Gases expand ..........than the liquids.

Fill in the blank

Alcohol expands ...........than water.

 Fill in the blank

Iron expands ............ than copper.

Match the column;

 Column A Column B
(a) Blowing air increases  (1) increase in inter - molecular separation
(b) Increase in pressure increases (2) pendulum of a clock
(c) Thermal expansion 

(3) Cooking utensils 

(d) Invar (4) boiling point 
(e) Pyrex glass (5) evaporation

select the correct alternative 

In evaporation

  1. all molecules of liquid begin to escape out
  2.  only the molecules at the surface escape out
  3.  the temperature of liquid rises by absorbing heat from surroundings.
  4.  the molecules get attracted within the liquid.

select the correct alternative 

The rate of evaporation of a liquid increases when :

  1. temperature of liquid falls
  2.  liquid is poured in a vessel of less surface area
  3.  air is blown above the surface of liquid
  4.  humidity increases.

select the correct alternative  

During boiling or vaporization

  1.  all molecules take part
  2.  temperature rises
  3.  no heat is absorbed
  4.  the average kinetic energy of molecules increases.

select the correct alternative 

The boiling point of a liquid is increased by

  1.  increasing the volume of liquid
  2.  increasing the pressure, on liquid
  3.  adding ice to the liquid
  4.  decreasing pressure on liquid.

select the correct alternative 

Two rods A and B of the same metal, but of length 1 m and 2 m respectively, are heated from 0°C to 100°C. Then

  1.  both the rods A and B elongate the same
  2.  the rod A elongates more than the rod B
  3.  the rod B elongates more than the rod A
  4.  the rod A elongates, but the rod B contracts.

select the correct alternative 

Two rods A and B of the same metal, same length, but one solid and the other hollow, are heated to the same rise in temperature.

  1.  the solid rod A expands more than the hollow rod B
  2.  the hollow rod B expands more than the solid rod A
  3.  the hollow rod B contracts, but the solid rod A expands
  4.  both the rods A and B expand the same.

select the correct alternative 

A given volume of alcohol and the same volume of water are heated from the room temperature to the same temperature then.

  1. alcohol contracts, but water expands
  2.  water contracts, but alcohol expands
  3.  water expands more than alcohol
  4.  alcohol expands more than water.

select the correct alternative 

The increase in length of a metal rod depends on

  1.  the initial length of the rod only
  2.  the rise in temperature only
  3.  the material of rod only
  4. all the above three factors.

select the correct alternative 

The correct statement is

  1.  Iron rims are cooled before they are placed on the cart wheels.
  2.  A glass stopper gets tighten on warming the neck of the bottle.
  3.  Telephone wires sag in winter, but become tight in summer.
  4.  A little space is left between two rails on a railway track.

Chapter 6: Heat Transfer solutions [Page 0]

What is matter ? What is it composed of.

Name the three states of matter and distinguish them on the basis of their (i) volume, and (ii) shape

Distinguish between liquid and vapour (or gas) states of matter on the basis of following factors
(a) Arrangement of molecules
(b) Inter-molecular separation
(c) Inter-molecular force, and
(d) Kinetic energy of molecules

What is evaporation ? Explain it on the basis of molecular motion.

Do all the molecules of a liquid take part in evaporation ? If not, explain your answer.

No heat is supplied to a liquid during evaporation. How does then the liquid change into its vapours ?

Comment on the statement ‘evaporation is a surface phenomenon’.

Why is cooling produced when a liquid evaporates ?

Give reason for the increase in rate of evaporation of a liquid when air is blown above the liquid.

Give reason for the increase in rate of evaporation of a liquid when surface area of liquid is increased.

Give reason for the increase in rate of evaporation of a liquid when temperature of liquid is increased.

What is boiling ? Explain it on the basis of molecular motion?

Why does bubbles appear when a liquid is heated ?

What is the change in average kinetic energy of molecules of a liquid during boiling at its boiling point ?

How is the heat energy supplied to a liquid used during boiling at a fixed temperature ?

Name two ways of change of liquid state to the vapour state and distinguish them.

What do you understand by thermal expansion of a substance ?

Give two examples of the substances which expand on heating.

Describe an experiment to demonstrate the thermal expansion in solids.

State three factors on which depend the linear expansion of a metal rod on heating.

Two iron rods – one 10 m long and the other 5 m long, are heated to the same rise in temperature. Which will expand more ?

Two identical rods of copper are heated to different temperatures — one by 5°C and the other by 10°C. Which rod will expand more ?

One rod of copper and another identical rod of iron are heated to the same rise in temperature. Which rod will expand more? Give reason.

Two identical rods—one hollow and the other solid, are heated to the same rise in temperature. Which will expand more ?

In the ball and ring experiment, ifthe ball after heating is left to cool on the ring for some time, the ball again passes through the ring. Explain the reason.

Explain the following:

The telephone wires break in winter.

Explain the following:
Iron rims are heated before they are fixed on the wooden wheels.

Explain the following:

The gaps are left between the successive rails on a railway track.

A glass stopper stuck in the neck of a bottle can be removed by pouring hot water on the neck of the bottle.

A cement floor is laid in small pieces with gaps in between.

Why is one end of a steel girder in a bridge kept on rollers instead of fixing it in pillar ?

A metal plate is heated. State three factors on which the increase in its area will depend.

A cubical metal solid block is heated. How will its volume change ?

Describe an experiment to show that liquids expand on heating.

State one application of thermal expansion of liquids.

Describe an experiment to showthat air expands on heating.

An empty glass bottle is fitted with a narrow tube at its mouth. The open end of the tube is kept in a beaker containing water. When the bottle is heated, bubbles of air are seen escaping into water. Explain the reason.

Which of the following will expand more, when heated to the same temperature : (a) solid (b) liquid and (c) gas ?

Describe an experiment to show that same volume of different liquids heated to same rise in temperature expand by different amounts.

100 ml of each of the following liquid is heated from 10°C to 50°C. Which will expand more : (a) water (b) benzene (c) alcohol ?

Water is heated from 0°C to 4°C. Will it expand ?

What do you mean by anomalous behaviour of water ?

How does the density of a substance (solid, liquid and gas) change on heating ?

An iron washer is heated. State the effect on its mass.

An iron washer is heated. State the effect on its internal diameter.

An iron washer is heated. State the effect on its external .

An iron washer is heated State the effect on its density.

Chapter 6: Heat Transfer

Selina Selina Concise Physics - Middle School Class 8 (2018-19 Session)

Selina Concise Physics - Middle School for Class 8 (2018-19 Session)

Selina solutions for Class 8 Physics chapter 6 - Heat Transfer

Selina solutions for Class 8 Physics chapter 6 (Heat Transfer) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CISCE Selina Concise Physics - Middle School for Class 8 (2018-19 Session) solutions in a manner that help students grasp basic concepts better and faster.

Further, we at shaalaa.com are providing such solutions so that students can prepare for written exams. Selina textbook solutions can be a core help for self-study and acts as a perfect self-help guidance for students.

Concepts covered in Class 8 Physics chapter 6 Heat Transfer are Difference Between Boiling and Evaporation, Thermal Expansion - Linear Expansion, Thermal Expansion - Volume Expansion, Thermal Expansion - Superficial Expansion, Compare Expansivity in Solids, Liquids and Gases, Thermal Expansion - Examples and Real World Applications.

Using Selina Class 8 solutions Heat Transfer exercise by students are an easy way to prepare for the exams, as they involve solutions arranged chapter-wise also page wise. The questions involved in Selina Solutions are important questions that can be asked in the final exam. Maximum students of CISCE Class 8 prefer Selina Textbook Solutions to score more in exam.

Get the free view of chapter 6 Heat Transfer Class 8 extra questions for Physics and can use shaalaa.com to keep it handy for your exam preparation

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