The temperature of the atmosphere at a high alititude is around `500^(@)C. Yet an animal there would freeze to death and not boil. Explain.

On an X temperature scale, water freezes at -125.0^(@) X and boils at 375.0^(@) X . On a Y temperature scale, water freezes at -70.0^(@)Y and boils at -30.0^(@)Y . The value of temperature on X-scale equal to the temperature of 50.0^(@)Y on Y-scale is

It has been recorded that the temperature of the earth’s atmosphere has increased by 0.6^@C . (a) What has caused this increase ? (b) Explain its consequences.

Water oozes out from a porous pot the pressure inside being 20 atmosphere more than that outside. If the temperature of the water inside be 10^(@)C , what would be the temperature of the water coming out? ( J=4.2 joules cal^(-1) , atmospheric pressure =1.05xx10^(5)Nm^(-2) )

Explain why : (a) A body with large reflectivity is a poor emitter. (b) A brass tumbler feels much colder then a wooden tray on a chilly day. (c ) an optical pyrometer (for measuring high temperatures) calibrated for an ideal black body correct value for the temperature when the same piece is in the furnace. (d) The earth without its atmosphere would be inshospitably cold. (e ) Heating system based on circulation of steam are more effecient in warming a building than those based on circulation of hot water.

Addition of non-volatile solute to solvent lowers its vapoure pressure. Therefore, the vapour pressure of a solution (i.e, V.P. of solvent in a solution) is lower than that of pure solvent in a solution) is lower than that of pure solvent, at the same temperature. A higher temperature is needed to raise the vapour pressure upto one atmosphere pressure, when boiling point is attined. However, increase in b.pt. is small . for example, 0.1 molal aqueous sucrose solution boils at 10.05^(@)C Sea water, an aqueous solution, which is rich in Na^(+) and Cl^(-) ions, freezes about 1^(@)C lower than frozen water . At the freezing point of a pure-solvent, the reates at which two molecule stick together to form the solid and leave it to return to liquid are equal when solute is present. Few solvent molecules are in contact with surface of solid. However, the rate at which the solvent molecules leave, surface of solid remains unchanged. That is why, temperature is lowered to restore the equalibrium. The freezing depression in a dilute solution is proportional to molality of the solute. The freezing point of benzene solution was 5.4^(@)C . The osmotic pressure of same solution at 10^(@)C is (freezing point of benzene = 5.5^(@)C ). Assume solution to be dilute. [ K_(f) for C_(6)H_(6) is 4.9 K "molality"^(-1) ].

On a cold winter dry, the temperature of atmosphere is -T^(@)C . The cylindrical dram shown is made of insultating material and it contains water at 0^(@)C . If L is latent heat of fusion of ice, rho is density of ice and K_(R) is thermal conductivity of ice, the time taken for total mass of water to freeze is