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$Δ Q = n C d T$ represents

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Important Questions on Thermal Properties of Matter

EASY

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

Two moles of oxygen is mixed with eight moles of helium. The effective specific heat of the mixture at constant volume is

HARD

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

A water cooler of storage capacity

120

litres can cool water at constant rate of

P

W

. In a closed circulation system (as shown schematically in the figure), the water from the cooler is used to cool an external device that generates constantly

3

kW

of heat (thermal load). The temperature of water fed into the device can not exceed

30^{o} C

and the entire stored

120

litres of water is initially cooled to

10^{o} C

. The entire system is thermally insulated. The minimum value of

P

(in

W

) for which the device can be operated for

3

hours is:

(Specific heat of water is

4.2 kJ

k g^{- 1} K^{- 1}

and the density of water is

1000 kg m^{- 3}

)

HARD

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

10.0 W

electrical heater is used to heat a container filled with

0.5 kg

of water. It is found that the temperature of the water and the container rise by

3 K

15

minutes. The container is then emptied, dried, and filled with

2 kg

of an oil. It is now observed that the same heater raises the temperature of the container-oil system by

2 K

20

minutes. Assuming no other heat losses in any of the processes, the specific heat capacity of the oil is

HARD

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

1 kg

of ice at

- 20^{o} C

is mixed with

2 kg

of water at

90^{o} C

. Assuming that there is no loss of energy to the environment, what will be the final temperature of the mixture? (Assume latent heat of ice

= 334.4 kJ {(kg)}^{- 1}

, specific heat of water and ice are

4.18 kJ {(kg - K)}^{- 1}

and

2.09 kJ {(kg - K)}^{- 1}

, respectively.)

HARD

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

A certain liquid has a melting point of

- 50 ° C

and a boiling point of

150 ° C

. A thermometer is designed with this liquid and its melting and boiling points are designated at

0 ° L

and

100 ° L

. The melting and boiling points of water on this scale are

HARD

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

20 g

bullet whose specific heat is,

5000 J {kg}^{- 1} {}^{\circ}C^{- 1}

and moving at,

2000 m s^{- 1}

plunges into a

1.0 kg

block of wax whose specific heat is,

3000 J {kg}^{- 1} {}^{\circ}C^{- 1}

. Both bullet and wax are at,

25 ° C

and assume that

(i)

the bullet comes to rest in the wax and

(ii)

all its kinetic energy goes into heating the wax. The thermal temperature of the wax in,

{}^{\circ}C

is close to.

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

An experiment takes

10 \min

to raise the temperature of water in a container from

0^{o} C

100^{o} C

and another

55 \min

to convert it totally into steam by a heater supplying heat at a uniform rate. Neglecting the specific heat of the container and taking specific heat of the water to be

1 cal {(g^{\circ} C)}^{- 1}

, the heat of vaporization according to this experiment will come out to be:

HARD

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

A current carrying wire heats a metal rod. The wire provides a constant power

(P)

to the rod. The metal rod is enclosed in an insulated container. It is observed that the temperature

(T)

in the metal rod changes with time

(t)

as:

T (t) = T_{0} (1 + β t^{\frac{1}{4}})

, where

β

is a constant with appropriate dimension while

T_{0}

is a constant with dimension of temperature. The heat capacity of the metal is:

EASY

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

The SI unit of mechanical equivalent of heat is

EASY

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

At what temperature do the Fahrenheit and Celcius scales of temperature coincide?

EASY

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

Ice is used in a cooler in order to cool its contents. Which of the following will speed up the cooling process?

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

Solar energy is incident normally on the earth's surface at the rate of about

1 .4 kW m^{- 2}

. The distance between the earth and the sun is

1 .5 \times 10^{11} m

. Energy

(E)

and mass

(m)

are related by the Einstein equation,

E = m c^{2}

where

c = (3 \times 10^{8} m s^{- 1})

is the speed of light in free space. The decrease in the mass of the sun is

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

Water of volume 2 L in a closed container is heated with a coil of 1 kW. While water is heated, the container loses energy at a rate of 160 J/s. In how much time will the temperature of water rise from 27^oC to 77^oC ? (Specific heat of water is 4.2 kJ/kg and that of the container is negligible).

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

Two different liquids of same mass are kept in two identical vessels, which are placed in a freezer that extracts heat from them at the same rate causing each liquid to transform into a solid. The schematic figure below shows the temperature T vs time t plot for the two materials. We denote the specific heat of materials in the liquid (solid) states to be $C_{L 1} (C_{S 1})$ and $C_{L 2} (C_{S 2})$ respectively.

Question Image

EASY

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

200 g

water is heated from

40^{o} C

60^{o} C

. Ignoring the slight expansion of water, the change in its internal energy is close to (Given specific heat of water

= 4184

J {kg}^{- 1} K^{- 1}

EASY

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

The specific heat of water

= 4200 J

{kg}^{- 1} K^{- 1}

and the latent heat of ice

= 3.4 \times 10^{5} J

{kg}^{- 1}

100 g

of ice at

0^{o} C

is placed in

200 g

of water at

25^{o} C

. The amount of ice that will melt as the temperature of water reaches

0^{o} C

is close to (in grams)

EASY

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

A calorimeter of water equivalent

20 g

contains

180 g

of water at

25 ° C

{}^{'}m^{'}

' grams of steam at

100 ° C

is mixed in it till the temperature of the mixture is

31 ° C

. The value of

m

is close to (Latent heat of water

= 540 cal g^{- 1}

, specific heat of water

= 1 cal g^{- 1 °} C^{- 1}

)

EASY

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

Pyrometer is a device for measuring

EASY

Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

Mercury is often used in clinical thermometers. Which one of the following properties of mercury is not a reason for this?

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Physics>Heat and Thermodynamics>Thermal Properties of Matter>Specific Heat Capacity and Molar Heat Capacity

A thin paper cup filled with water does not catch fire when placed over a flame. This is because

ΔQ=nCdT represents

Important Questions on Thermal Properties of Matter

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$Δ Q = n C d T$ represents