EASY
Earn 100

Place a Pyrex glass funnel with its mouth-down in a saucepan full of water, in such a way that the stem tube of the funnel is above the water or pointing upward into the air. Rest the edge of the bottom portion of the funnel on a nail or on a coin, so that water can get under it. Place the pan on a stove and heat it till it begins to boil. Where do the bubbles form first? Why? Can you explain how a natural geyser works using this experience?

Important Questions on Thermal Properties of Matter

EASY
Two systems are in thermal equilibrium. The quantity which is common for them is
EASY
Latent heat of vaporisation of water is 22.6×105 J kg-1. The amount of heat needed to convert 100 kg of water into vapour at 100 °C is
HARD
A 10 H inductor carries a current of 20 A. If the energy stored in this inductor melts ice at 0 °C, then the mass of the ice melted is [Latent heat of ice =2.26×103 J kg-1
MEDIUM
A solid metal weighing 150 g melts at its melting point of 800 °C by providing heat at the rate of 100 W. The time taken for it to completely melt at the same temperature is 4 min. What is the specific latent heat of fusion of the metal?
EASY
A closed bottle containing water at 30oC is open on the surface of the moon. Then-
HARD

Explain the following temperature versus time graph:

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MEDIUM
50 g of ice at 0 °C is mixed with 50 g of water at 80 °C. If the latent heat of ice is 80 cal g-1 and specific heat of water is 1 cal g-1 °C-1, then the final temperature of mixture is
EASY
If minimum possible work is done by a refrigerator in converting 100 grams of water at 0 °C to ice, how much heat (in calories) is released to the surroundings at temperature 27 °C (Latent heat of ice= 80 Cal/gram) to the nearest integer?
MEDIUM
A thermally insulated vessel contains 150 g of water at 0°C . Then the air from the vessel is pumped out adiabatically. A fraction of water turns into ice and the rest evaporates at 0°C itself. The mass of evaporated water will be closest to: (Latent heat of vaporization of water =2.10×106 J kg-1 and Latent heat of Fusion of water =3.36×105 J kg-1 )
MEDIUM
1 kg of water, at 20 °C is heated in an electric kettle whose heating element has a mean (temperature averaged) resistance of 20Ω. The rms voltage in the mains is 200 V. Ignoring heat loss from the kettle, time taken for water to evaporate fully is close to
[ Specific heat of water =4200 J kg-1 °C-1 Latent heat of water =2260 kJ kg-1 ]
EASY
The physical quantity that determines whether or not a given system A is in thermal equilibrium with another system B is called
EASY
A piece of ice falls from a height h so that it melts completely. Only one-quarter of the heat produced is absorbed by the ice and all energy of ice gets converted into heat during its fall. The value of h is:
(Latent heat of ice is 3.4×105J kg-1 and g=10N kg-1)
EASY

A steam engine intakes 50 g of steam at 100°C per minute and cools it down to 20°C. If latent heat of vaporization of steam is 540 cal g-1, then the heat rejected by the steam engine per minute is _____ ×103 cal

(Given : specific heat capacity of water : 1 cal g-1C-1)

EASY

Heat required to melt 1 g of ice is 80 cal. A man melts 60 g of ice by chewing in one minute. His power is______

HARD

A thermally insulated cubical box of side length 20 cm and wall thickness 2 cm containing 2 kg of ice is closed on all sides. The mass of ice melted in 10 hours is (Thermal conductivity of the material of the box =0.01 Wm-1 K-1, latent heat of ice =360×103 J kg-1 and ambient temperature =40 °C)

EASY
Coefficient of linear expansion of brass and steel rods are α1 and α2. Lengths of brass and steel rods are l1 and l2, respectively. If l2-l1 is maintained the same at all temperatures, which one of the following relations holds good?
HARD
Two rectangular blocks, having identical dimensions, can be arranged either in configuration  I or in configuration II as shown in the figure. One of the blocks has thermal conductivity K and the other 2 K . The temperature difference between the ends along the x-axis is the same in both the configurations. It takes 9 s to transport a certain amount of heat from the hot end to cold end in the configuration I . The time to transport the same amount of heat in the configuration II is

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MEDIUM
Steam at 100 oC is passed into 20 g of water at 10 oC. When water acquires a temperature of 80oC, the mass of water present will be:
[Take specific heat of water =1 cal g-1 oC-1 and latent heat of steam =540 cal g-1]
EASY
In an experiment, a sphere of aluminium of mass 0.20 kg is heated up to 150°C . Immediately, it is put into water of volume 150 cc at 27oC kept in a calorimeter of water equivalent to 0.025 kg . The final temperature of the system is 40oC . The specific heat of the aluminium is(take 4.2 Joule=1 calorie )
EASY
If pressure increased on a piece of wax, the melting point of wax