Matter in Our Surrounding Test - 10

Cooling is not caused during boiling. The normal room temperature is 298K or.25^∘C Evaporation is a surface phenomenon but boiling is a bulk phenomenon. The liquid having low boiling points evaporate faster.

Melting point is defined as the constant temperature at which the solid and the liquid phases of substance coexist.

Evaporation of water increase with the increase in temperature, surface area and wind speed but decrease with increase in humidity. So, the larger humidity will decrease the rate of evaporation.

A desert cooler cools better on a hot and dry day because on a hot dry day temperature is high and humidity is less which helps in better evaporation. Due to the higher rate of evaporation it gives better cooling effect.

By touching the surface of china dish. This is due to the fact that to change from liquid to the vapour state, alcohol requires latent heat of vaporisation. the alcohol takes this heat of vaporisation from china dish. The china dish loses heat and gets cooled.

Evaporation of ether occurs due to absorption of heat by surrounding. So, it is an endothermic process.The chemical reaction in which heat is absorbed in called as an endothermic reaction. The reaction in which heat is evolved is called exothermic reaction and the reaction in which no thermal changes occur is called athermic process.

Naphthalene, camphor, iodine and ammonium chloride are sublime substance. So, statement B is correct. Petrol, ether, acetone and carbon tetrachloride are volatile liquid but water is not a volatile liquid.

The process of changing solid directly into gases without changing into liquid is called sublimation.sugar, urea and ice are not sublime substance, only Iodine is a sublime substance.

The latent heat does not increase the kinetic energy of the particles of the substance. and since there is no increase in the kinetic energy of the particles,the temp. of a substance does not rise during the change of state.When the liquid starts boiling, the further heat energy which is supplied is absorbed as latent heat of vaporisation by the liquid to change its state of matter.

Evaporation is a surface phenomenon as takes place only on the surface of liquid. Particles from the surface gain enough energy to overcome the forces of attraction present in the liquid and change into the vapour state. On the other hand, boiling is a bulk phenomenon. Particles from the bulk (whole) of the liquid change into vapour state.

The intermixing of particles of two different types of matter on their own is called diffusion. On heating, diffusion becomes faster. At a given temperature, the rate of diffusion of gases varies inversely as the square root of their densities.