NCERT Solutions for Class 11 Physics Chapter 10 Thermal Properties of Matter

NCERT Solutions for Class 11 Physics Chapter 10 Thermal Properties of Matter

Vishal kumarUpdated on 19 Sep 2025, 01:35 AM IST

Have you never observed that a chair made of metal is colder than one made of wood, though both are at the same temperature? Or why blacksmiths heat rims of iron and put them in wooden wheels? This is explained in Chapter 10 - Thermal Properties of Matter of Class 11 Physics. This chapter presents the concept of heat, temperature, thermal expansion, calorimetry, specific heat capacity and various methods used in transferring heat, such as conduction, convection, and radiation.

This Story also Contains

  1. Thermal Properties of Matter NCERT Solutions: Download Solution PDF
  2. Thermal Properties of Matter NCERT Solutions - Exercise Questions
  3. Class 11 Physics Chapter 10 - Thermal Properties of Matter: Higher Order Thinking Skills (HOTS) Questions
  4. Class 11 Physics Chapter 10 - Thermal Properties of Matter: Topics
  5. Class 11 Physics Chapter 10 - Thermal Properties of Matter: Important Formulae
  6. What Extra Should Students Study Beyond NCERT for JEE/NEET?
  7. NCERT Solutions for Class 11 Physics Chapter-Wise
  8. NCERT solutions for class 11 subject-wise
NCERT Solutions for Class 11 Physics Chapter 10 Thermal Properties of Matter
NCERT SOlution for class 11 chapter 10 thermal properties of matter

NCERT Solutions for Class 11 Physics Chapter 10 - Thermal Properties of Matter are made by experienced teachers, and it is presented in a step-by-step explanation of all the questions in the exercise. These NCERT solutions make complicated concepts much easier, enhance problem-solving abilities and enable students to relate theory with practical life examples such as boiling water, land winds, sea winds or thermal conductivity of metals. They are very useful in CBSE board examinations and competitive exams of JEE, NEET, and Olympiads are also good preparation material. These NCERT Solutions for Class 11 Physics Chapter 10 - Thermal Properties of Matter should be practised regularly so that a firm foundation is laid and the performance in exams is enhanced.

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Thermal Properties of Matter NCERT Solutions: Download Solution PDF

The Class 11 Physics Chapter 10 - Thermal Properties of Matter question answers can be downloaded as a free PDF file and hence allow students to prepare for exams easily. The solutions are in steps and are made in accordance with the recent CBSE syllabus and facilitate fast revision. Here, the download link of the Class 11 Physics Chapter 10 - Thermal Properties of Matter NCERT Solutions PDF is provided, which you can study and practice very easily without any complications.

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Thermal Properties of Matter NCERT Solutions - Exercise Questions

The Thermal Properties of Matter class 11 question answers address every question in the exercises with step-by-step explanations. Students develop an insight into topics such as heat transfer, heat expansion, and specific heat, and can solve numerical problems, and prepare better to take board exams, JEE, and NEET.

Q. 10.1 The triple points of neon and carbon dioxide are 24.57K and 216.55K respectively. Express these temperatures on the Celsius and Fahrenheit scales.

Answer:

The relation between the Kelvin and Celsius scales is T K = T C + 273.15

Triple Point of Neon in Kelvin T K = 24.57 K

Triple Point of Neon in Celcius T C = T K -273.15 = 24.57 -273.15 =-248.58 o C

Triple Point of carbon dioxide in Kelvin T K = 216.55 K

Triple Point of carbon dioxide in Celcius T C = T K -273.15 = 216.55 - 273.15 = -56.60 o C

The relation between Celsius and Fahrenheit scales is TF=95TC+32

Triple Point of Neon in Fahrenheit is

TF=95×(248.58)+32

T F = -415.44 o C

Triple Point of carbon dioxide in Fahrenheit is

TF=95×(56.60)+32

T F = -69.88 o C

Q. 10.2 Two absolute scales A and B have triple points of water defined to be 200A and 350B . What is the relation between TA and TB ?

Answer:

200 A = 273 K

TK=273200TA

350 B = 273 K

TK=273350TB

Equating T K from the above two equations, we have

273200TA=273350TB


TA=47TB

Q. 10.3 The electrical resistance in ohms of a certain thermometer varies with temperature according to the approximate law:R=R0[1+α(TT0)] The resistance is 101.6Ω at the triple-point of water 273.16K, and 165.5Ω at the normal melting point of lead (600.5K). What is the temperature when the resistance is 123.4Ω?

Answer:

R=R0[1+α(TT0)]

R 0 = 101.6Ω

T 0 = 273.16K

R = 165.5Ω

T = 600.5K

Putting the above values in the given equation, we have

α=165.5101.6600.527316

α=1.92×102 K1

For R = 123.4Ω

T=T0+1α(RR01)

T=273.16+11.92×102(123.4101.61)

T=384.75K

Q. 10.4 (a) Answer the following:
The triple-point of water is a standard fixed point in modern thermometry. Why ? What is wrong in taking the melting point of ice and the boiling point of water as standard fixed points (as was originally done in the Celsius scale)?

Answer:

Unlike the melting point of ice and the boiling point of water, the triple point of water has a fixed value of 273.16 K. The melting point of ice and the boiling point of water vary with pressure.

Q. 10.4 (c) Answer the following :

The absolute temperature (Kelvin scale) T is related to the temperature tc on the Celsius scale by tc=T273.15. Why do we have 273.15 in this relation, and not 273.16?

Answer:

This is because 0 °C on the Celsius scale corresponds to the melting point at standard pressure is equal to 273.15 K, whereas 273.16 K is the triple point of water. The triple point of water is 0.01oC, not 0 °C

Q. 10.4 (d) Answer the following :

What is the temperature of the triple-point of water on an absolute scale whose unit interval size is equal to that of the Fahrenheit scale?

Answer:

Let at a certain temperature, the readings on the Fahrenheit and Kelvin Scales be T F and T K, respectively

TF32=95(TK273) (i)

Let at another temperature, the reading on the Fahrenheit and Kelvin Scales be T' F and T' K respectively

TF32=95(TK273) (ii)

Subtracting equation (ii) from (i)

TFTF=95(TKTK)

For T K - T' K = 1 K,

T F - T' F = 9/5

Therefore, corresponding to 273.16 K, the absolute scale whose unit interval size is equal to that of the Fahrenheit scale

TF=95×273.16

TF=491.688

Q. 10.5 (a) Two ideal gas thermometers A and B use oxygen and hydrogen respectively. The following observations are made :

Temperature
Pressure
Thermometer A
Pressure
Thermometer B
Triple-point of water
Normal melting point of sulphur

What is the absolute temperature of the normal melting point of sulphur as read by thermometers A and B?

Answer:

PV=nRT

PT=nRV

As the moles of oxygen and hydrogen inside the thermometers and the volume occupied by the gases remain constant, P/T would remain constant.

The triple point of water(T 1 ) = 273.16 K

Pressure in thermometer A at a temperature equal to the triple point of water (P 1 ) = 1.250×105Pa

Pressure in thermometer A at a temperature equal to the Normal melting point of sulphur (P 2 ) = 1.797×105Pa

The normal melting point of sulphur, as read by thermometer A, T2, would be given as

T2=P2T1P1

T2=1.797×105×273.161.250×105

T2=392.69 K

Pressure in thermometer B at a temperature equal to the triple point of water (P1' ) = 0.200×105Pa

Pressure in thermometer B at a temperature equal to the Normal melting point of sulphur (P2' ) = 0.287×105Pa

The normal melting point of sulphur, as read by thermometer B, T2' would be given as

T2=P2T1P1

T2=0.287×105×273.160.200×105

T2=391.98 K

Q. 10.5 (b) Two ideal gas thermometers A and B use oxygen and hydrogen respectively. The following observations are made :

Temperature
Pressure
Thermometer A
Pressure
Thermometer B
Triple-point of water
Normal melting point of sulphur

What do you think is the reason behind the slight difference in the answers of thermometers A and B? (The thermometers are not faulty.) What further procedure is needed in the experiment to reduce the discrepancy between the two readings?

Answer:

The slight difference in the answers of thermometers A and B occurs because the gases used in the thermometers are not ideal gases. To reduce this discrepancy, the experiments should be carried out at low pressures where the behaviour of real gases tends closer to that of ideal gases.

Q. 10.6 A steel tape 1m long is correctly calibrated for a temperature of 27.0C. The length of a steel rod measured by this tape is found to be 63.0cm on a hot day when the temperature is 45.0C. What is the actual length of the steel rod on that day? What is the length of the same steel rod on a day when the temperature is 27.0C? Coefficient of linear expansion of steel =1.20×105K1.

Answer:

At 27 oC, the 63 cm (l1) mark on the steel tape would be measuring exactly 63 cm as the tape is calibrated at 27 o C

Coefficient of linear expansion of steel =1.20×105K1.

Actual length when the scale is giving a reading of 63 cm at 45 oC is l2

l2=l1(1+αΔT)=63×(1+1.20×105×(4527))=63.013608cm

The actual length of the steel rod on a day when the temperature is 45 °C is 63.013608 cm.

Length of the same steel rod on a day when the temperature is 63°C.

Q. 10.7 A large steel wheel is to be fitted on to a shaft of the same material. At 27C , the outer diameter of the shaft is 8.70cm and the diameter of the central hole in the wheel is 8.69cm . The shaft is cooled using ‘dry ice’. At what temperature of the shaft does the wheel slip on the shaft? Assume coefficient of linear expansion of the steel to be constant over the required temperature range : αsteel=1.20×105K1 .

Answer:

Diameter of the steel shaft at 27 o C (T 1 ) d 1 = 8.70 cm

The diameter of the central hole in the wheel, d2 = 8.69 cm

Coefficient of linear expansion of the steel αsteel=1.20×105K1.

The wheel will slip on the shaft when the diameter of the steel shaft becomes equal to the diameter of the central hole in the wheel.

Let this happen at temperature T

d2=d1(1+α(TT1))8.69=8.7(1+1.2×105(T27))

T=68.79 oC

Q. 10.8 A hole is drilled in a copper sheet. The diameter of the hole is 4.24cm at 27.0C. What is the change in the diameter of the hole when the sheet is heated to 227C? Coefficient of linear expansion of copper =1.70×105K1.

Answer:

Coefficient of linear expansion of copper α =1.70×105K1.

Coefficient of superficial expansion of copper is β

β=2α

β=2×1.7×105

β=3.4×105K1

Diameter of the hole at 27 o C (d 1 ) = 4.24 cm

Area of the hole at 227 o C is

A2=A1(1+βΔT)

A2=π(4.242)2(1+3.4×105(22727))
A2=14.215 cm2

Let the diameter at 227 oC be d 2

π(d24)2=14.215

d2=4.254cm

Change in diameter is d 2 -d 1 = 4.24 -4.254 = 0.014 cm.

Q. 10.9 A brass wire 1.8m long at 27C is held taut with little tension between two rigid supports. If the wire is cooled to a temperature of 39C, what is the tension developed in the wire if its diameter is 2.0mm? Co-efficient of linear expansionofbrass=2.0×105K1; Youngsmodulusofbrass=0.91×1011Pa.

Answer:

Young's Modulus of Brass, Y=0.91×1011

Coefficient of linear expansion of Brass, α=2.0×105K1

The diameter of the given brass wire, d = 2.0 mm

Length of the given brass wire, l = 1.8 m

Initial Temperature T 1 = 27 o C

Final Temperature T 2 = -39 o C

Y=StressStrain

Y=FAΔll

F=ΔlAYl

F=(lαΔT)AYl

F=αΔTAY

F=αΔTYπd24

F=2.0×105×(3927)×0.91×1011×π×(2×103)24

F=378N

The tension developed in the wire is 378 N. The negative sign signifies that this tension is inward.

Q. 10.10 A brass rod of length 50cm and diameter 3.0mm is joined to a steel rod of the same length and diameter. What is the change in length of the combined rod at 250C, if the original lengths are at 40.0C? Is there a ‘thermal stress’ developed at the junction? The ends of the rod are free to expand (Coefficient of linear expansionofbrass=2.0×105K1,steel=1.2×105K1 ).

Answer:

Length of the rods l = 50 cm

Coefficient of linear expansion of brass, αb=2×105K1

Coefficient of linear expansion of steel, αs=1.2×105K1

Initial Temperature T 1 = 40.0 o C

Final Temperature T 2 = 250 o C

Change in the length of the brass rod is

Δlb=ltαbΔT

Δlb=50×2.0×105×(25040)

Δlb=0.21cm

A change in the length of the steel rod is

Δls=lsαsΔT

Δls=50×1.2×105×(25040)

Δls=0.126cm

Change in the length of the combined rod is

Δl=Δls+Δlb

Δl=0.126+0.21

Δl=0.336cm

Q. 10.11 The coefficient of volume expansion of glycerine is 49×105K1. What is the fractional change in its density for a 30C rise in temperature?

Answer:

Coefficient of volume expansion of glycerine is γ=49×105K1

Let the initial volume and mass of a certain amount of glycerine be V and m, respectively.

Initial density is

ρ=mV

Change in volume for a 30 oC rise in temperature will be

ΔV=V(γΔT)

ΔV=V(49×105×30)

ΔV=0.0147V

Final Density is

ρ=mV+ΔV

ρ=m1.0147V

ρ=0.986mV

Fractional Change in density is

ρρρ=0.986mvmvmv=0.014

The negative sign signifies that with an increase in temperature, density will decrease.

Q. 10.12 A 10kW drilling machine is used to drill a bore in a small aluminium block of mass 8.0kg. How much is the rise in temperature of the block in 2.5 minutes, assuming 50o/o of power is used up in heating the machine itself or lost to the surrounding. Specificheatofaluminium=0.91Jg1K1.

Answer:

Power of the drilling machine, P = 10 kW

Time. t = 2.5 min

Total energy dissipated, E, is

E=Pt

E=10×103×2.5×60

E=1.5×106J

The thermal energy absorbed by the aluminium block is

ΔQ=E2

ΔQ=1.5×1062

ΔQ=7.5×105J

Mass of the aluminium block, m = 8.0 kg

Specific heat of aluminium, c = 0.91 J g -1 K -1

Let the rise in temperature be ΔT

mcΔT=ΔQ

ΔT=ΔQmc

ΔT=7.5×1050.91×8×103

ΔT=103.02 oC

Q. 10.13 A copper block of mass 2.5kg is heated in a furnace to a temperature of 500C and then placed on a large ice block. What is the maximum amount of ice that can melt? (Specific heat of copper =0.39Jg1K1; heat of fusion of water =335Jg1 ).

Answer:

Mass of copper block m = 2.5 kg

Initial Temperature of the copper block, T 1 = 500 o C

Final Temperature of Copper block, T 2 = 0 o C

Specific heat of copper, c = 0.39 J g -1 K -1

Thermal Energy released by the copper block is ΔQ

ΔQ=mcΔT

ΔQ=2.5×103×0.39×500

ΔQ=487500 J

Latent heat of fusion of water, L = 335 J g -1

The amount of ice that can melt is

w=ΔQL

w=487500335

w=1455.22g

1.455 kg of ice can melt using the heat released by the copper block.

Q. 10.14 In an experiment on the specific heat of a metal, a 0.20kg block of the metal at 150 °C is dropped in a copper calorimeter (of water equivalent 0.025kg ) containing 150cm3 of water at 27C. The final temperature is 40C. Compute the specific heat of the metal. If heat losses to the surroundings are not negligible, is your answer greater or smaller than the actual value for specific heat of the metal?

Answer:

Let the specific heat of the metal be c.

Mass of metal block m = 200 g

Initial Temperature of the metal block = 150 o C

Final Temperature of the metal block = 40 o C

The heat released by the block is

ΔQ=mcΔT

ΔQ=200×c×(15040)

ΔQ=22000c

Initial Temperature of the calorimeter and water = 27 °C

Final Temperature of the calorimeter and water = 40 °C

Amount of water = 150 cm

Mass of water = 150 g

Water equivalent of calorimeter = 25 g

Specific heat of water = 4.186 J g -1 K -1

Heat absorbed by the Calorimeter and water is ΔQ

ΔQ=(150+25)×4.186×(4027)

ΔQ=9523.15J

The heat absorbed by the Calorimeter and water is equal to the heat released by the block

ΔQ=ΔQ22000c=9523.15c=0.433 J g1 K1

The above value would be less than the actual value since some heat must have been lost to the surroundings as well, which we haven't accounted for.

Q. 10.15 Given below are observations on molar specific heats at room temperature of some common gases.

Gas Molar specific heat (Cv)

(calmol1K1)

Hydrogen 4.87

Nitrogen 4.97

Oxygen 5.02

Nitric oxide 4.99

Carbon monoxide 5.01

Chlorine 6.17

The measured molar specific heats of these gases are markedly different from those for monatomic gases. Typically, the molar specific heat of a monatomic gas is 2.92cal/molK.. Explain this difference. What can you infer from the somewhat larger (than the rest) value for chlorine?

Answer:

Monoatomic gases have only a translational degree of freedom, but diatomic gases have rotational degrees of freedom as well. The temperature increases with an increase in the spontaneity of motion in all degrees. Therefore, to increase the temperature of diatomic gases, more energy is required than that required to increase the temperature of monoatomic gases by the same value, owing to higher degrees of freedom in diatomic gases.

If we only consider rotational modes of freedom, the molar specific heat of the diatomic gases would be given as

c=fR2


c=52×1.92


c=4.95 cal mol1 K1

The number of degrees of freedom = 5 (3 translational and 2 rotational)

The values given in the table are more or less in accordance with the above calculated ones. The larger deviation from the calculated value in the case of chlorine is because of the presence of vibrational motion as well.

Q. 10.16 A child running a temperature of 101F is given an antipyrin (i.e. a medicine that lowers fever) which causes an increase in the rate of evaporation of sweat from his body. If the fever is brought down to 98F in 20 minutes, what is the average rate of extra evaporation caused, by the drug. Assume the evaporation mechanism to be the only way by which heat is lost. The mass of the child is 30kg. . The specific heat of human body is approximately the same as that of water, and latent heat of evaporation of water at that temperature is about 580calg1 .

Answer:

Initial Temperature of the boy = 101°F

Final Temperature of the boy = 98°F

Change in Temperature is

ΔT=3 oF

ΔT=3×59

ΔT=1.67 oC

Mass of the child is m = 30 kg

Specific heat of human body = 1000 cal kg -1 °C -1

Heat released is ΔQ

ΔQ=mcΔT

ΔQ=30×1000×1.67

ΔQ=50000 cal

Latent heat of evaporation of water = 580 cal g -1

The amount of heat lost by the boy has been absorbed by the water.

Let the mass of water which has evaporated be m'

ΔQ=mL

m=QL

m=50000580

m=86.2 g
Time in which the water has evaporated, t = 20 min.

The rate of evaporation is m'/t

mt=86.220

mt=4.31 g min1

Q. 10.17 A ‘thermacole’ icebox is a cheap and an efficient method for storing small quantities of cooked food in summer in particular. A cubical icebox of side 30 cm has a thickness of 5.0cm. If 4.0kg of ice is put in the box, estimate the amount of ice remaining after 6 h. The outside temperature is 45C. and co-efficient of thermal conductivity of thermacole is 0.01Js1m1K1. [Heatoffusionofwater=335×103Jkg1]

Answer:

Side of the box s = 30 cm

Area available for conduction A

A = 6s 2

A=6(30) 2

A=5400 cm 2 = 0.54 m 2

Temperature difference = 45 o C

Coefficient of thermal conductivity of thermacole is k = 0.01 J s -1 m -1 K -1

Width of the box is d = 5 cm

Heat absorbed by the box in 6 hours is ΔQ

ΔQ=kAΔTl

ΔQ=0.01×0.54×45×6×60×600.05

ΔQ=104976 J

The heat of fusion of water is L=335×103 J kg1

The amount of ice which has melted is m'

m=ΔQL

m=104976335×103

m=0.313 kg

Amount of ice left after 6 hours = 4 - 0.313 = 3.687 kg

Q. 10.18 A brass boiler has a base area of 0.15m2 and thickness 1.0cm. It boils water at the rate of 6.0kg/min when placed on a gas stove. Estimate the temperature of the part of the flame in contact with the boiler. Thermal conductivity of brass =109Js1m1K1; Heat of vaporisation of water =2256×103Jkg1.

Answer:

The rate at which water boils, R = 6.0 kg min -1

The heat of vaporisation of water, L=2256×103 J kg1

The rate at which heat enters the boiler

dQdT=RL

dQdT=6×2256×10360

dQdT=2.256×105Js1

The base area of the boiler, A = 0.15 m 2

Thickness, l = 1.0 cm

Thermal conductivity of brass =109Js1m1K1;

The temperature inside the boiler = Boiling point of water = 100 o C

Let the temperature of the flame in contact with the boiler be T

The amount of heat flowing into the boiler is

dQdt=KAΔTl2.256×105=109×0.15×(T100)1×102T100=137.98T=237.98C

The temperature of the flame in contact with the boiler is 237.98 o C

Q. 10.19 (a) Explain whya body with large reflectivity is a poor emitter

Answer:

A body with a large reflectivity is a poor absorber. As we know, a body which is a poor absorber will also be a poor emitter. Therefore, a body with large reflectivity is a poor emitter.

Q .10.19 (b) Explain whya brass tumbler feels much colder than a wooden tray on a chilly day

Answer:

Brass is a good conductor of heat. Therefore, once someone touches brass, the heat from their body flows into it, and it feels cold. In the case of a wooden tray, no such conduction of heat from the body takes place, as wood is a very poor conductor of heat.

Q. 10.19 (c) Explain why an optical pyrometer (for measuring high temperatures) calibrated for an ideal black body radiation gives too low a value for the temperature of a red hot iron piece in the open but gives a correct value for the temperature when the same piece is in the furnace

Answer:

An optical pyrometer relates the brightness of a glowing body to its temperature. In the open, because of other sources of light, the sensor in the optical pyrometer does not detect the true brightness of a red hot piece of iron and thus does not predict its temperature correctly, whereas in the furnace, the piece of iron is the only source of light and the sensor detects its brightness correctly thus giving the correct value of the temperature.

Q. 10.19 (d) Explain why the Earth without its atmosphere would be inhospitably cold

Answer:

The sun's rays contain infrared radiation. These are reflected back by the lower part of the atmosphere after being reflected by the surface of the Earth and are trapped inside the atmosphere, thus maintaining the Earth's temperature at a hospitable level. Without these rays being trapped, the temperature of the Earth would go down severely, and thus the Earth without its atmosphere would be inhospitably cold.

Q. 10.19 (e) Explain why heating systems based on the circulation of steam are more efficient in warming a building than those based on the circulation of hot water

Answer:

Heating systems based on the circulation of steam are more efficient in warming a building than those based on the circulation of hot water because the same amount of steam at 100 °C contains more energy available for heat dissipation than the same amount of water at 100 °C in the form of latent heat of vaporisation.

Q. 10.20 A body cools from 80C to 50C in 5 minutes. Calculate the time it takes to cool from 60C to 30C. The temperature of the surroundings is 20C.

Answer:

Let a body initially be at temperature T 1

Let its final Temperature be T 2

Let the surrounding temperature be T 0

Let the temperature change over time t.

According to Newton's Law of Cooling

dTdt=K(TT0)

dTTT0=Kdt

T1T2dTTT0=K0tdt


[ln(TT0)]T1T2=K[t]0t


ln(T2T0T1T0)=Kt

where K is a constant.

We have been given that the body cools from 80 o C to 50 o C in 5 minutes when the surrounding temperature is 20 o C.

T 2 = 50 o C

T 1 = 80 o C

T 0 = 20 o C

t = 5 min = 300 s.

ln(50208020)=K×300K=ln(2)300

For T 1 = 60 o C and T 2 = 30 o C we have

ln(30206020)=ln2300t


t=ln(4)×300ln(2)


t=2ln(2)×300ln(2)


t=600 s


t=10 min

The body will take 10 minutes to cool from 60 o C to 30 o C at the surrounding temperature of 20 o C.

Class 11 Physics Chapter 10 - Thermal Properties of Matter: Higher Order Thinking Skills (HOTS) Questions

The Class 11 Physics NCERT Chapter 10 HOTS (Higher Order Thinking Skills) Questions are designed to challenge students’ understanding of thermal properties of matter beyond textbook exercises. These questions encourage critical thinking, application-based learning, and problem-solving skills, preparing students for competitive exams like JEE and NEET.

Q1: When 100 g of liquid A at 100oC is added to 50 g of liquid B at a temperature of 75oC, the temperature of the mixture becomes 90oC. The temperature of the mixture (in oC), if 100 g of liquid A at 100oC is added to 50 g of liquid B at 50oC, will be :

Answer:

Specific Heat -

S=QmΔθ - wherein S= specific heat Δθ= Change in temperature m= Amount of mass For (I) 100×SA×(10090)=50×SB×(9075)SA=1.52SB=34SB(1) now for (II)100×SA×(100T)=50×SB×(T50)2SA(100T)=SB(T50)(2)
From (1) & (2)

2×34×(100T)=(T50)3(100T)=2(T50)3003T=2T100400=5TT=80C


Q2: If the length of cylinder on heating increases by 2% then the area of base of cylinder will increase by

Answer:

Assuming the initial length of the cylinder is 1, the linear expansion coefficient is α, and the temperature rise is ΔtC,

Δ=αΔtΔ×100=αΔt×1002=αΔt×100


Now, for the area

ΔA=AβΔtΔAA=βΔtΔAA×100=βΔt×100% change in area =βΔt×100=βΔt×100


We know that 2×α×Δt=β×Δt

=2αΔt×100=2(αΔt×100)=2×2=4%


Q3: A cylindrical metal rod of length L0 is shaped into a ring with a small gap, as shown inthe Figure. On heating the system,

A. x will decrease, r will increase

B. Both x and r will decrease

C. Both x and r will increase

D. r will increase, x will remain the same

Answer:

Linear Expansion - When a solid is heated and its length increases, then the Expansion is called linear Expansion.
On the heating, the system x and r both will increase since the expansion of isotropic solids is similar to true photographic enlargement.


Q4: The coefficient of thermal expansion of a rod varies with temperature as α=α0+α0TT0 where T is the temperature of the body and all others are positive constants. If the temperature of the rod of length 0 is changed from T0/2 to T0 uniformly with time, then what is the ratio of the rate of fractional change of length initially and finally?

Answer:

We know the coefficient of thermal expansion is given as

dLL dT=αdLLdt=αdT dt(dLLdt)1(dLLdt)2=α1dTdtα2dTdt(dLLd)1(dLLdt)2=α1α2α0+α0T0/2T0α0+α0T0T0=3/22=34


Q5: A red-hot iron (mass 25 g) has a temperature of 100ºC. It is immersed in a mixture of ice and water at thermal equilibrium. The volume of the mixture is found to be reduced by 0.15 cm3with the temperature of the mixture remains constant. Find the specific heat (in cal gm 0C) of the metal.

Given specific gravity of ice = 0.92, specific gravity of water at 0C=1.0, latent heat of fusion of ice =80calg1.

Answer:

As the ice melts, its density changes, which causes change in volume. Let m g of ice melt.

mρicemρH2O=0.15m=0.15×0.920.08Hlost =Hgaired 25×S×100=0.15×0.920.08×80S=0.06calgmC


Class 11 Physics Chapter 10 - Thermal Properties of Matter: Topics

Chapter 10: Thermal Properties of Matter: Key topics include heat, temperature, thermal expansion and heat conduction. The chapter describes temperature-dependent behaviour of matter and the physics behind the phenomena we experience in our daily lives, such as the boiling of water, expansion of metals and sea breezes. These are the basic points of thermodynamics to understand and the applications in real life.

10.1 Introduction
10.2 Temperature And Heat
10.3 Measurement Of Temperature
10.4 Ideal-Gas Equation And Absolute Temperature
10.5 Thermal Expansion
10.6 Specific Heat Capacity
10.7 Calorimetry
10.8 Change Of State
10.8.1 Latent Heat
10.9 Heat Transfer
10.9.1 Conduction
10.9.2 Convection
10.9.3 Radiation
10.9.4 Blackbody Radiation
10.10 Newton’s Law of Cooling

Class 11 Physics Chapter 10 - Thermal Properties of Matter: Important Formulae

Thermal Properties of Matter class 11 question answers include all essential equations related to heat, temperature, thermal expansion, and heat transfer. These formulas help students solve numerical problems effectively and are crucial for board exams, JEE, NEET, and other competitive tests. Mastery of these formulas simplifies the understanding and application of thermal concepts.

1. Heat and Temperature Relation

Q=mcΔT
Where:

Q= heat added or removed m= mass c= specific heat capacity ΔT= change in temperature

2. Specific Heat Capacity

c=QmΔT

3. Heat Capacity

C=mcC=QΔT

4. Latent Heat

Q=mL
Where:
L= latent heat of fusion or vaporisation
(Use for phase changes with no temperature change)

5. Linear, Areal and Volume Expansion

ΔL=LαΔT

ΔA=AβΔT
Where β=2α


ΔV=VγΔT
Where γ=3α

8. Calorimetry Principle

Heat lost=Heat gained
(Applies to thermal equilibrium problems)

9. Thermal Conduction

Q=kA(T1T2)td


Where:
k= thermal conductivity
A= area
d= thickness
t= time
T1T2= temperature difference

10. Newton’s Law of Cooling

dTdt(TTenv )

Approach to Solve Questions of Class 11 Physics Chapter 10 - Thermal Properties of Matter

To solve the problems presented in Class 11 Physics Chapter 10 - Thermal Properties of Matter, one should pay attention to the application of concepts instead of memorisation of formulae. The questions in this chapter tend to challenge your capacity to relate heat, temperature and expansion of heat to real-life scenarios. A logical step-by-step method will enable students not only to simplify issues, but also to prevent the confusion of various processes in heat transfer and to develop precision in board exams and in competitive examinations.

  • Have a Clear Conceptual Understanding. Revise the simple terms like heat, temperature, specific heat, thermal expansion, and types of heat transfer.
  • Categorise the Kind of Problem. Find out whether the question involves temperature change, thermal expansion, heat capacity, phase change or heat transfer.
  • These should be Calculated Using the Appropriate Formula. Choose the right formula according to the topic
  • Apply conduction, convection, and radiation formulae where necessary.
  • Convert Units, if required. Put everything in SI (e.g. mass as kg, temperature in Kelvin, time in seconds).
  • Use the principle of Calorimetry: Heat lost=Heat gained
  • Include Latent Heat in the case of Phase Change. Remember to add or delete latent heat in melting, boiling or condensation questions.

What Extra Should Students Study Beyond NCERT for JEE/NEET?

This comparison table shows the divergence between textbook focus, depth and the kind of questions that are asked in a competitive examination like JEE and NEET on the topic of thermal properties of matter. NCERT gives a good conceptual knowledge along with a basic practice set, whereas JEE/NEET questions require application of techniques, application-based reasoning and advanced numerical practice. This table assists the students in areas they need to focus on in preparation of the exams.

Frequently Asked Questions (FAQs)

Q: What is the theme of the chapter 10 in NCERT?
A:

Thermal properties of matter describe the behaviour of substances when heat is added or removed, such as temperature changes, expansion, heat transfer and phase changes.

Q: Why is a metal chair colder than a wooden chair of the same temperature?
A:

Metals are good conductors of heat and hence they tend to conduct heat away at a very fast rate from our body and thus they feel colder, whereas wood is a poor conductor and does not conduct heat at a high rate.

Q: What is the difference between heat and temperature?
A:

Heat is a type of energy that is exchanged between bodies with respect to a difference in temperature whereas temperature is a measure of how hot or cold a body is.

Q: Why is specific heat capacity useful in the solution of numerical problems?
A:

Specific heat capacity is used to establish the amount of heat energy needed to increase the temperature of one unit mass of a substance by 1 °C (or 1 K), commonly encountered in calculations-based questions.

Q: Is this chapter valuable in the competitive examinations such as JEE and NEET?
A:

Yes, a lot of conceptual and numerical questions, depending on the heat transfer, thermal expansion, and calorimetry, are regularly asked in JEE, NEET, and other entrance tests.

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