Explain the following : (i) Most metal oxides are insoluble in water but some of these dissolve in water, what are these oxides and their solutions in water called? (ii) At ordinary temperature, the surface of metals such as magnesium, aluminiumand zinc etc, is covered with a thin layer. What is the composition of this layer? State its importance. (iii) Some alkali metals can be cut with a knife.

Explain the following : (i) Most metal oxides are insoluble in water

1.	Explain the following : (i) Most metal oxides are insoluble in water but some of these dissolve in water, what are these oxides and their solutions in water called? (ii) At ordinary temperature, the surface of metals such as magnesium, aluminiumand zinc etc, is covered with a thin layer. What is the composition of this layer? State its importance. (iii) Some alkali metals can be cut with a knife.
Answer» Solution :(i) These OXIDES are called basic oxides and their solutions in water are called ALKALIS. (ii) This layer formed is protective oxide layer which PREVENTS the metals from further oxidation. (iii) Some alkali can be CUT with a knife because they are very soft and have LOW densities.