• facebook
  • twitter
  • whatsapp
  • telegram

THERMAL PROPERTIES OF MATTER

 Questions - Answers

Very Short Answer Type Questions

1. Do values of coefficient of expansion differ, when the temperatures are measured on Centrigarde scale or on Fahrenheit scale?

A: Yes. One degree interval on Fahrenheit scale is less than one degree interval on Celsius scale


                            
2. Can a substance contract on heating? Give an example.

A: Yes. Substance will contract on heating.

e.g: Leather, Cast Iron, Rubber.
 

3. Why gaps are left between rails on a railway track?

A: To compensate expansion of rails during summer, a gap is left in between ends of two successive rails.
 

4. Why do liquids have no linear and areal expansion?

A: Liquids have only volume expansion. They do not have their own shape, they occupy the shape of the container. Hence they do not have linear and areal expansions.

5. What is latent heat of fusion?

A: The amount of heat energy absorbed to convert unit mass of ice at 0°C into water at   0°C is known as latent heat of fusion.

      Lice = 80 Cal / gm = 3.33 × 105 J/kg.
 

6. What is latent heat of vapourisation?

A: The amount of heat energy required to unit mass of water at 100°C to steam at 100°C   is known as latent heat of vapourisation.

      LVapour = 540 Cal/ gm, 22.6 × 105 J/kg.
 

7. What is specific gas constant? Is it same for all gases?

A: Universal gas constant per unit mass is called specific gas constant 'r'. It's value changes from gas to gas.
 

8. Why utensils are coated black? Why the bottom of utensils are made of Copper?

A: Since black bodies are good absorbers of heat so lower portion of utensil is  coated black. Copper is a good conducter of heat. It promotes the distribution of heat over the bottom of the vessel for uniform cooking.

9. State Wein's displacement law.

A: Wavelength (λm) of maximum intensity of emission of a black body radiation is inversely proportional to absolute temperature (T) of the black body.

b is Wein's constant.
 

10. Does the body radiate heat at 0°K? Does it radiate heat at 0°C?

A: No, the body does not radiate heat at 0° K. Yes, the body radiate heat at 0°C.
 

11. State different modes of transmission of heat. Which of these modes require medium.

A: There are three different modes of heat transfer.

     1) Conduction     2) Convection     3) Radiation Conduction, Convection require medium.
 

12. What is thermal resistance of a conductor? On what factors does it depend?

A: The resistance offered by the conductor for the flow of heat through it is called 'Thermal resistance'.


It depends on:  i) nature of the material           ii) geometry of the object.

 

13. What is green house effect? Explain global warming?

A: Green house effect: Green house effect is a process by which thermal radiation from earth's surface is absorbed by atomspheric gases (CO2, Methane, Nitrous oxide) and is re-radiated in all directions. The part of this re-radiation is back towards the surface. Which results in heating up of earth's surface and atmosphere.

Global warming: Concentration of green house gases enhanced due to human activities making earth warmer. Which cause problems for human life, plants and animals.
 

14. Roof of buildings are often painted white during summer. Why?
A: White colour is a good reflector of heat. Good reflector is a bad absorber of heat. So buildings are kept cool during summer.

 

Long Answer Type Questions (8 Marks)
 

1. State Boyle's law, Charles's law. Hence derive ideal gas equation. Which of the two laws is better for purpose of thermometry and why?
A: Boyle's Law: At constant temperature, the pressure of given mass of a gas is

inversely proportional to its volume.


                               
Charles's Law: At constant pressure, the volume of given mass of a gas is directly proportional to its temperature on Kelvin scale.


                              
Ideal gas: A gas which obeys Boyle's law and Charles's law at all temperatures and pressures is called an Ideal gas. Ideal gas equation is:

Consider one mole of an ideal gas at a pressure P1, volume V1 and temperature T1. By applying Boyle's law pressure is changed from P1 to P2, volume is changed from V1 to V at constant temperature (T1). Then

By applying Charles's law, volume is changed from V to V2 and temperature is changed from T1 to T2. Then,


       
Where 'r' is Specific gas constant.

2. (a) State and explain Newton's law of cooling. State the conditions under which Newton's law of cooling is applicable?

(b) A body cools down from 60°C to 50°C in 5 min and to 40°C in another 8min. Find the temperature of surroundings.

A: Newton's law of cooling: Rate of loss of heat of a hot body is directly proportional to the differnce of temperature of the body and surroundings.

Explanation: Loss of heat by radiation depends upon the nature of the surface of the body and area of the exposed surface. T, Ts are temperatures of hot body and surroundings respectively.


 Newton's law of cooling is applicable when
(i) Loss of heat is negligible by conduction
(ii) Heat lost by body is mainly by convection
(iii) Temperatue of every part of the body is same
(iv) Temperature differences are moderate.

Posted Date : 30-10-2021

గమనిక : ప్రతిభ.ఈనాడు.నెట్‌లో కనిపించే వ్యాపార ప్రకటనలు వివిధ దేశాల్లోని వ్యాపారులు, సంస్థల నుంచి వస్తాయి. మరి కొన్ని ప్రకటనలు పాఠకుల అభిరుచి మేరకు కృత్రిమ మేధస్సు సాంకేతికత సాయంతో ప్రదర్శితమవుతుంటాయి. ఆ ప్రకటనల్లోని ఉత్పత్తులను లేదా సేవలను పాఠకులు స్వయంగా విచారించుకొని, జాగ్రత్తగా పరిశీలించి కొనుక్కోవాలి లేదా వినియోగించుకోవాలి. వాటి నాణ్యత లేదా లోపాలతో ఈనాడు యాజమాన్యానికి ఎలాంటి సంబంధం లేదు. ఈ విషయంలో ఉత్తర ప్రత్యుత్తరాలకు, ఈ-మెయిల్స్ కి, ఇంకా ఇతర రూపాల్లో సమాచార మార్పిడికి తావు లేదు. ఫిర్యాదులు స్వీకరించడం కుదరదు. పాఠకులు గమనించి, సహకరించాలని మనవి.

Special Stories

More

విద్యా ఉద్యోగ సమాచారం

More
 

లేటెస్ట్ నోటిఫికేష‌న్స్‌