Question

if a fresh egg is put into a beaker filled with water it sinks . On dissolving a lot of salt in the water , the egg begins to rise and then floats .Why ?

Answer 1

when you immerse the egg in water the density of water will be less than that of the egg and thus the egg sinks 
  when you put some salt in it it increases the density of water ans thus when you immerse the egg the density of egg will be lesser than the water's density and it thus sinks
              
                              hope it helps you..............

Answer 2

1-the density of egg is more than water
2-so first the egg sinks
3-after adding salt the water becomes more denser than the egg
4-hence the density of egg is less than water
5-so it floats after adding salt

 objects of density less than water floats on water and objects of density greater than water sinks in water..