karan bisht (30)

GIVE REASON

Q-NAPTHALENE BALLS DISAPPEAR WITH TIME WITHOUT LEAVING ANY SOLID?

ans-because napthalene balls sublime and directly change into vapour state without leaving any solid 

we can get the smell of perfumesitting several meters away?

ANS-because in perfume they contaion voltile solvent and diffused faster and can reach seveeal meter away

Q- Arrange the following substances  in increasing order of force of attracting between the particles water,suger,oxygen.
 Ans oxygen,water and suger.

Q    what is trhe physical state of water at-
Ans (a) 25c is liquid
        (b) 0c is solid or liquid.
        (c) 100c is liquid and vapour.

Q    Give reason
(a) water at  room temperature is a liquid.
(b) An iron almirah is a solid at room temperature.

Ans  (a)  water at  room temperature is a liquid beacuse its freezing point is 0c and boiling point is                      100c.
       (b) An iron almirah is a solid at room temperature because melting point of iron isa higher than                 room temperature

Q    Why is ice at 273 k more effective in cooling than water at the same temperature ?
Ans   Ice at 273 k Will take latent heat from the medium to overcome the fusion and then after gaining some more heat, it will become water, hence the cooling effect of ice is more than the water at same temperature because water does not take this extra heat  from the medium .

Q  What produces more serve burns, boiling water or steam?
Ans  Steam at 100c will produce more servere burns as it has extra heat hidden in it called  latent heat whereas the boiling water does not have this hidden heat.