11

Q1. Water has maximum density at

• 4^o C
• 4^o K
• 4^o K
• 0^o C

Solution

Water has maximum density at 4 ^oC.

Q2. Newton's law of cooling states that the rate of cooling of a body is proportional to the _____________________.

• temperature of the body
• temperature of the surroundings
• temperature of the body + temperature of the surroundings
• excess temperature of the body over the surroundings.

Solution

Newton's law of cooling states that the rate of cooling of a body is proportional to the excess temperature of the body over the surroundings. That is, dT/dt is proportional to ΔT

Q3. Which of the following relation implies Boyle's law?

• PV = constant
• V/T = constant
• PV = RT
• PV = nRT

Solution

When temperature remains constant, the pressure and the volume of a quantity of gas is related as PV = constant. This relationship is known as Boyle's law.

Q4. If the volume of a block of metal changes by 0.10%, when it is heated through 20^oC, then the coefficient of linear expansion of metal is:

• 1.66 x 10^{-5 o}C^-1
• 2.66 x 10^{-5 o}C^-1
• 2 x 10^{-5 o}C^-1
• 1 x 10^{-5 o}C^-1

Solution

Q5. Rate of conduction of heat depends on:

• Area of cross section
• Temperature difference
• Material
• Both a and b

Solution

Rate of conduction of heat depends on a.     Area of cross section b.     Temperature difference  

Q6. Water contracts on heating between the temperatures

• 0^oC to 4^oC
• 0^oF to 4^oF
• 0^oK to 4^oK
• 0 K to 273 K

Solution

Water contracts on heating between the temperatures 0^oC to 4^oC due to its anomalous behaviour.

Q7. SI unit of thermal conductivity is

• Jm^-1s^-1K^-1
• J m s K^-1
• J s^-1 K
• J s K

Solution

The SI unit of thermal conductivity is Jm^-1s^-1K^-1.

Q8. The process by which heat is transferred from one place to another without heating the intervening medium is known as

• Convection
• Radiation
• Fusion
• Sublimation

Solution

The process by which heat is transferred from one place to another without heating the intervening medium is known as radiation.

Q9. Fusion takes place when

• Liquid changes to solid
• Solid changes to Liquid
• Liquid changes to Gas
• Solid changes to Gas

Solution

The change of state from solid to liquid is called fusion.

Q10. When the temperature of a substance increases, what happens to the speed of the molecules?

• stays the same
• increases
• decreases
• not measureable

Solution

When the temperature is increased, the supplied energy excites the molecules, thus increasing their speed.

Q11. Which of the given phenomena is not related to convection?

• Formation of trade winds
• Maintaining comfortable room temperature in cold countries
• In winter metallic handles appear colder than wooden door
• Formation of land and sea breezes

Solution

Formation of trade winds, land and sea breezes are phenomena related to convection whereas phenomenon in which metallic handle becomes colder than the wooden door is an example of conduction of heat.

Q12. A copper ball weighing 400 gm is put in a furnace with 1000 gm water at 20 °C. The temperature of water increases to 80 °C at equilibrium. Find the temperature of the furnace. The specific heat of copper is 0.1 cal/gm/k and that of water is 1.0 cal/gm/K.

• 2.4 K
• 240 K
• 1580^o C
• 1500^o C

Solution

Let T be the temperature of the furnace. According to the law of calorimetry, we have Heat lost by copper = heat gained by water 400 × 0.1 × (T - 80) = 1000 × 1 × 60 T - 80 = 1580 T = 1500 °C

Q13. The temperature at which the liquid and the vapour states of the substance coexist is called its

• Boiling point
• Melting point
• Freezing Point
• Fusion point

Solution

The temperature at which the liquid and the vapour states of the substance coexist is called its boiling point.

Q14. A steel tape is calibrated at 20^o C. A piece of wood is being measured by steel tape at 10^o C and reading is 30 cm on the tape. The real length of the wood is:

• more than 30 cm
• less than 30 cm
• Equal to 30 cm
• cannot be predicted

Solution

The steel tape contract on cooling, therefore the real length of wood piece would be greater than 30 cm.

Q15. A solid body of constant heat capacity 1 J/°C is being heated by keeping it in contact with reservoirs in two ways: (i)   Sequentially keeping in contact with 2 reservoirs such that each reservoir supplies same amount of heat. (ii)  Sequentially keeping in contact with 8 reservoirs such that each reservoir supplies same amount of heat. In both the cases body is brought from initial temperature 100 °C to final temperature 200 °C. Entropy change of the body in the two cases respectively is:

• ln2, 4ln2
• ln2, ln2
• ln2, 2ln2

Solution

Irrespective of the arrival of the system to an equilibrium state, entropy describes quantitatively an equilibrium state of thermodynamics system. Hence, entropy is a state function. Therefore changes in both the given processes should be same. 

Q16. In a steady state, temperature of each part of rod is

• Constant and same
• Not constant
• Constant but not same
• Varies with time

Solution

In a steady state, the temperature of each part of the rod is constant but not the same.

Q17. Which phase of matter has maximum value of temperature coefficient of cubical expansion?

• Solid
• Liquid
• Gaseous
• All have the same coefficient.

Solution

Gaseous phase has maximum value of temperature coefficient of cubical expansion.

Q18. The amount of heat required to raise the temperature of one mole of an ideal mono atomic gas through 2^oC at constant pressure is (universal gas constant = R)

• 2 R
• 3 R
• 5 R
• 5R/2

Solution

Q19. Which is the fastest mode of heat transfer?

• Conduction
• Radiation
• Convection
• Transition

Solution

The fastest mode of heat transfer is radiation.

Q20. What happens to the volume of the substance when the temperature increases?

• stays the same
• increases
• decreases
• not measureable

Solution

When temperature of a substance increases, the molecules start moving vigorously in all directions, thus expanding and increasing the volume.

Q21. The process by which heat flows from the region of higher temperature to the region of lower temperature by actual movement of material particles is called

• Conduction
• Convection
• Radiation
• Sublimation

Solution

The process by which heat flows from the region of higher temperature to the region of lower temperature by actual movement of material particles is called convection.

Q22. How many grams of ice at -14 °C are needed to cool 200 gram of water from 25 °C to 10 °C? Take latent heat of ice = 80 cal g^-1 and specific heat of ice = 0.5 cal g^-1 °C^-1.

• 30 g
• 25 g
• 31 g
• 35 g

Solution

Heat lost by water in cooling from 25 °C to 10 °C is Q = mc ΔT = 200 x 1 x (25 - 10) = 3000 cal Heat gained by ice at -14 °C to change into water at 10 °C is Q = (mc ΔT)_ice + mL + (mc ΔT)_water    = (m x 0.5 x 14) + (m x 80) + (m x 1 x 10)    = 97m cal By the principle of calorimetry, we have 97 m = 3000 Therefore, the mass of the ice to be added = 3000/97 = 31 g 

Q23. Phenomenon in which solid directly changes into vapour is called

• Fusion
• Vaporization
• Triple point
• Sublimation

Solution

Phenomenon in which solid directly changes into vapour is called sublimation.

Q24. A student added a drop of red food colouring to 4 beakers of water. Each beaker contained 100 ml of water at different temperatures. The student recorded how long it took each beaker to mix completely (without stirring). The following table shows her results:   Beaker Temperature of water Time to mix 1 10 °C 120 sec 2 25 °C 55 sec 3 40 °C 40 sec 4 80 °C 23 sec What conclusion should the student make from this experiment about the movement of the particles?   

• They move slowly in warm water so they mix faster
• They move slowly in warm water so they mix slowly
• They move faster in warm water so they mix faster
• They move faster in warm water so they mix slowly

Solution

Particles are moving faster in warm water and so they mix at a faster rate.

Q25. The temperature at which the solid and the liquid states of the substance are in thermal equilibrium with each other is called its

• Melting point
• Fusion point
• Boiling point
• Freezing point

Solution

The temperature at which the solid and the liquid states of the substance are in thermal equilibrium with each other is called its melting point.

Q26. A device in which heat measurement can be made is called

• Calorimeter
• Joule meter
• Thermal meter
• Gauge meter

Solution

A device in which heat measurement can be made is called Calorimeter.

Q27. The value of ice and steam point on Fahrenheit temperature scale is

• 32 ^oF and 200 ^oF
• 32 ^oF and 212 ^oF
• 30 ^oF and 212 ^oF
• 0 ^oF and 100 ^oF

Solution

The value of ice and steam point on Fahrenheit temperature scale is 32 ^oF and 212 ^oF

Q28. The temperature for which the reading on Celsius and Fahrenheit scales are identical is

• -273 ^oC, -273 ^oF
• -30 ^oC,  -30 ^oF
• 0 ^oC, 0 ^oF
• -40 ^oC,  -40 ^oF

Solution

Let T_C and T_F = x 

Q29. A faulty thermometer reads 5 ^oC in melting ice and 105 ^oC in steam. The correct temperature in ^oF when the faulty thermometer reads 50 ^oC is

• 113 ^oF
• 123 ^oF
• 122 ^oF
• 120 ^oF

Solution

As the lowest and the highest point on the faulty thermometer are 5 ^oC and 105 ^oC, so

Q30. What is the velocity of radiation?

• 3 X 10⁶ m/s
• 3 X 10⁸ m/s
• 3 X 10⁷ m/s
• 3 X 10⁹ m/s

Solution

The velocity of radiation is same as the velocity of light, i.e. c = 3 X 10⁸ m/s.

Q31. A decrease in temperature in a liquid would change it to which of the following?

• Solid
• Liquid
• Gas
• Plasma

Solution

Decreasing the temperature of a liquid, decreases the average K.E. of the molecules, thus bringing them closer and binding them tightly; due to which the liquid changes into a solid.

Q32. Four cylindrical rods of different radii and lengths are used to connect two heat reservoirs at fixed temperatures t₁ and t₂ respectively. From the following pick out the rod which will conduct the maximum quantity of heat:

• Radius 1 cm, length 1 m
• Radius 1 cm, length 2 m
• Radius 2 cm, length 4 m
• Radius 3 cm, length 8 m

Solution

The quantity of heat conducted is given as Hence, we can see that the quantity of heat is directly proportional to the area of cross-section and inversely proportional to the length of the rod. Comparing rod 1 and 2: Area is same and length of 2 is double that of 1. Hence, rod 1 conducts better. So, comparing rod 1 and 3: Area of 2 is 4 times that of 1, but length is also 4 times that of 1. So, both the rods conduct equally. So, comparing 1 and 4: Area of rod 4 is 9 times that of 1, however its length is 8 times more. So, rod 4 is a better conductor. Hence, rod 4 is the best conductor amongst the 4 rods.

Q33. SI unit of latent heat is

• J Kg
• J/Kg
• J Kg ^-2
• Cal/ Kg

Solution

SI unit of latent heat is J/Kg.

Q34. A piece of iron of mass 0.2 kg is kept inside a furnace, till it attains the temperature of the furnace. The hot piece of iron is then dropped into a calorimeter containing 0.24 kg of water at 20°C. The mixture attains an equilibrium temperature of 60°C.  The temperature of the furnace is

• 400 °C
• 406.80 °C
• 506.80  °C
• 500 °C

Solution

Let θ₁ be temperature of the furnace that is temperature of the piece of iron. Thus, the heat lost by piece of iron is Q = M₁C₁ (θ₁ - θ)    = 0.2 × 470 (θ₁ - 60) = 94 (θ₁ - 60) Heat gained by water and calorimeter is Q = (M₂ + w) × c₂ × (θ - θ2)    = (0.24 + 0.01) × 4200 × (60 - 20) = 42000 From above two equations 94 (θ₁ - 60) = 42000 θ₁ = 506.80 °C

Q35. The temperature and pressure at which all three phases of a substances coexist is called

• Fusion point
• Sublimation point
• Melting Point
• Triple point

Solution

The temperature and pressure at which the fusion curve, the vaporisation curve and the sublimation curve meet and all the three phases of a substance coexist is called the triple point of the substance.

Q36. Among the following methods of heat transfer, gravity does not play any part in

• Convection
• Convection and Conduction
• Radiation and Conduction
• Radiation

Solution

Gravity does not play any part in radiation and conduction because in both these processes heat is transferred without any motion of the medium particles. However, in convection heat is transmitted through the substance from one point to another due to the motion of the heated particles of the substance. These heated particles are affected by gravity.

Q37. If the temperature difference between the body and surrounding is small, then the rate of loss of heat is directly proportional to

• Pressure difference of the body
• Size of the two bodies
• Temperature of two bodies
• Nature of two bodies

Solution

If the temperature difference between the body and surrounding is small, then rate of loss of heat is directly proportional to the temperature of two bodies.

Q38. An increase in temperature in a liquid would cause a phase change to which of the following?

• Solid
• Liquid
• Gas
• Plasma

Solution

Increasing the temperature of liquid, increases the average K.E. of the molecules. The molecules start moving vigorously in all the directions, thereby increasing and the inter-molecular space between them. Thus, the liquid changes into gas.

Q39. A bottle of perfume is opened and the smell travels across the room. What does this observation suggest about the particles of the perfume?

• They move faster when they are cold
• They move slowly when cold
• They are always in motion and can travel
• They are large enough to see with a microscope

Solution

Particles of the perfume (or a medium) are always in motion and can travel.

Q40. Value of absolute Zero on Celsius scale is equal to

• 273 .5 K
• 273.15 K
• -273.15 ^oC
• 273.15 ^oC