MEDIUM
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Give the reason behind the increase in kinetic energy on particles with increase in temperature.

Important Questions on Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.

HARD
The melting point of naphthalene is 80°C and the room temperature is 30°C. A sample of liquid naphthalene at 100°C is cooled down to the room temperature. Draw a temperature time graph to represent this cooling. In the graph, mark the region which corresponds to the freezing process.
HARD
An ideal gas undergoes isothermal compression from 5 m3 to 1 m3 against a constant external pressure of 4 N m-2. The heat released in this process is 24 J mol-1K-1 and is used to increase the pressure of 1 mole of Al. The temperature of Al increases by:
HARD
An earthen pitcher used in summer cools water in it essentially by evaporation of water from its porous surface. If a pitcher carries 4 kg of water and the rate of evaporation is 20 g per hour, temperature of water in it decreases by Δ T in two hours. The value of Δ T is close to (ratio of latent heat of evaporation to specific heat of water is 540 °C )
 
HARD
1 kg of ice at -20oC is mixed with 2 kg of water at 90oC . 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.)
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)
MEDIUM
The qualitative sketches I, II and III given below show the variation of surface tension with molar concentration of three different aqueous solutions of KCl, CH3OH  and CH3CH211OSO3- Na+ at room temperature. The correct assignment of the sketches is -

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HARD
A reversible cyclic process for an ideal gas is shown below. Here, P, V, and T are pressure, volume and temperature, respectively. The thermodynamic parameters q, w, H and U are heat, work, enthalpy and internal energy, respectively.

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The correct option(s) is (are)
MEDIUM
A Carnot freezer takes heat from water at 0oC inside it and rejects it to the room at a temperature of 27oC. The latent heat of ice is 336×103 Jkg-1. If 5kg of water at 0oC is converted into ice at 0oC by the freezer, then the energy consumed by the freezer is close to :
HARD
Assume that a drop of a liquid evaporates by a decrease in its surface energy so that its temperature remains unchanged. The minimum radius of the drop for this to be possible is. (The surface tension is T, the density of the liquid is ρ and L is its latent heat of vaporisation.)